Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings

Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings Roohollah Babaei-Mahani, Ali Fereidounpour, Yinghe He, Peter Scholes This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8732040/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract Drilling operations generate large volumes of drill cuttings contaminated with hydrocarbons, salts, and trace metals, creating significant environmental and regulatory challenges for offshore disposal. Most regulatory frameworks prohibit the discharge of drill cuttings containing more than 1 wt.% oil‑on‑cuttings, necessitating effective on‑site treatment technologies. This study evaluates the performance of a continuous hybrid microwave–infrared thermal desorption process for the remediation of oil‑contaminated drill cuttings. Offshore water‑based drill cuttings contaminated with sour crude oil were collected from Middle Eastern drilling operations and treated using a pilot‑scale unit under inert, low‑oxygen conditions. The process achieved oil-removal efficiencies of 95.0–97.8%, consistently reducing oil on cuttings to below 1 wt.%. Total Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) were reduced by more than 96% across all samples. Thermogravimetric analysis confirmed that most volatile contaminants were removed at temperatures below 110°C, indicating a lower thermal demand than conventional thermal treatments. The results demonstrate that hybrid microwave/infrared thermal processing is an effective and energy‑efficient approach for the treatment of offshore drill cuttings, enabling regulatory compliance while minimising secondary emissions and operational disruption. drill cuttings treatment microwave/infrared processing environmental risk mitigation waste management drill cuttings processor offshore ecosystem protection Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Highlights • Continuous hybrid microwave-infrared thermal desorption of drill cuttings. • Oil removal efficiencies > 95% with final oil‑on‑cuttings < 1 wt.%. • Low‑temperature contaminant removal confirmed by TGA analysis. • Applicable to offshore drilling waste management. Introduction Background and context The volume of drill cuttings waste generated during oil and gas exploration and production can exceed 5,000 cubic meters per well, depending on several critical factors (Biltayib et al. 2016). Drill cuttings are pieces of rock brought to the surface during drilling operations by the action of drilling bits. The physical and chemical properties of drill cuttings depend on the type of drill bits, drilling mud, penetration rate, formation types, and additives used. Proper management of drill cuttings waste is essential to mitigate environmental impacts and comply with national and international regulations. The factors influencing drilling waste generation include the type of formation, well depth, borehole diameter, drilling fluid selection, solid control equipment, formation porosity, and borehole washout. Harder formations typically yield fewer cuttings than softer formations. Deeper wells and larger boreholes contribute to increased volumes of cuttings. The type of drilling fluid, water-based, oil-based, or synthetic-based, affects the volume and the environmental compatibility of the cuttings. Formation porosity also plays an important role in the volume of cuttings produced. Higher porosity formations generate fewer cuttings. Another critical factor is borehole washout, which occurs when the actual size of the wellbore is larger than the drill bit size due to the collapse or erosion of the formation during drilling. Washout is particularly prevalent in loose or weak formations, such as shale or unconsolidated sands, which are prone to erosion. This results in increased volumes of cuttings. Larger washout percentages directly correspond to greater waste volumes, making this a key consideration in waste management strategies. Various methods exist for disposal and management of drill cuttings; each presents specific challenges. Landfarming (Ball et al. 2012 ) spreads cuttings over land, mixing them with soil to promote bioremediation. This technique is most suitable for waste derived from water-based muds, as oil-based contamination can pose significant environmental harm. Injection of cuttings into subsurface formations (veil et al. 1996 ) offers secure containment, as long as both specialized equipment and suitable geological zones are available. However, this method essentially transfers the pollution from the surface to deeper geological layers, raising concerns about long-term environmental impacts. Biodegradation (Semple et al. 2003 ) employs microorganisms to break down hydrocarbons, but it proceeds more slowly and with less effectiveness when dealing with heavily contaminated or resistant materials such as high-molecular-weight aromatics, tars, or weathered oil residues. For oil-based drill cuttings, combining surfactant-based washing with subsequent biodegradation has been shown to significantly reduce residual hydrocarbons, illustrating the potential of integrated biological approaches (Yan et al. 2011 ). Solidification immobilizes contaminants, but cannot fully prevent leaching and may itself introduce further pollutants, especially under changing environmental conditions (Negata, 2003), such as acid rain, fluctuations in pH, or cyclic wetting and drying. Incineration at high temperatures can effectively neutralize many hazardous contaminants and greatly reduce waste volume, but it is energy-intensive and must be accompanied by stringent control of air emissions to avoid the release of toxic by-products. These observations are consistent with broader reviews of thermal treatment of hydrocarbon-impacted soils, which emphasise the trade-off between temperature, residence time, and environmental performance (Liu et al. 2023 ). Field experience has shown that optimising drilling waste treatment trains and matching technologies to local discharge criteria is essential for achieving regulatory compliance at acceptable cost (Mueller et al. 2013 ). Recent developments have explored microwave technology as a treatment method for drill cuttings. The advantage of microwave processes is rapid, localized heating, which can decompose hydrocarbons and reduce contamination (Pereira et al. 2014 ). Most published research, however, concerns experimental or batch-scale tests. To date, continuous microwave systems have not matched the required capacity for real-world drilling rates (Mota et al. 2018 ). The scale-up and design of continuous microwave systems for oil-contaminated drill cuttings have been investigated, highlighting both the potential of this technology and the engineering challenges associated with continuous operation (Robinson et al. 2010 ). For instance, prototype units achieve treatment rates well below those produced during active drilling. Further optimization for continuous operation and scale-up is needed to realize industrial application. Overall, current management techniques for drill cuttings suffer from scalability or environmental trade-offs. This study introduces a novel processing method, aiming to address current limitations with improved efficiency and sustainability. Literature Review Microwave technology has emerged as a highly effective method for treating drill cuttings contaminated with synthetic and oil-based drilling fluids. This technology leverages microwaves' unique ability to heat materials volumetrically, providing rapid and uniform heating that is not achievable with conventional thermal methods. Pereira et al. ( 2014 ) demonstrated that microwave radiation could reduce n-paraffin content in cuttings contaminated with non-aqueous fluids (NAFs) to below the discharge limit of 6.9% by mass, making it a viable option for on-site decontamination. Similarly, Mota et al. ( 2018 ) explored the kinetics of batch microwave drying of drill cuttings contaminated with an olefin-based fluid and achieved significant reductions in drying time and energy consumption, particularly at lower power settings. Their studies have shown that microwave heating promotes selective heating at the molecular level, providing advantages such as energy efficiency and shorter drying times. For instance, microwave drying technology allows the reuse of the recovered organic phase in the preparation of a new load of drilling fluid, as it does not alter the chemical composition of the fluid. Microwave heating produced more porous solid residues that enhanced heat and mass transfer during the treatment process, leading to greater mass loss and lower residual oil content in the treated cuttings (Celik et al. 2019 ). Several studies have compared microwave and infrared technologies to conventional thermal methods such as electric heating. Microwave heating has been shown to produce more porous solid residues, which enhance heat and mass transfer during the treatment process. This leads to greater mass loss and lower residual oil content in the treated cuttings (Junior et al. 2019). In addition to these studies, microwave drying of drilled cuttings has been shown to recover drilling fluid while reducing waste volume, further supporting the feasibility of microwave-based remediation (Santos 2014). In contrast, electric heating relies on the thermal conductivity of the material and the heat transfer efficiency in the system, which can be less effective for decontaminating drill cuttings. Previous work on the thermal treatment of drill cuttings has also identified scale-up, energy consumption, and off-gas handling as key design constraints for commercial systems (Rossi 2016 ). Additionally, the use of microwave technology has shown that it can promote the pyrolysis of petroleum hydrocarbons, making it more suitable for treating oil-based drilling cuttings (Hou et al. 2018 ). Microwave technology offers a promising solution for the treatment of drill cuttings contaminated with synthetic and oil-based fluids. Its ability to provide rapid, uniform heating with reduced energy consumption and environmental impact makes it a superior alternative to traditional thermal methods. However, challenges such as scaling up the technology for continuous processing need to be addressed to fully realise its potential in industrial applications. Further research into the optimization of process parameters and the design of continuous microwave treatment systems is necessary. The integration of microwave technology with existing oil and gas operations can significantly reduce the environmental footprint of drilling activities and provide a sustainable method for the remediation of drill cuttings. Regulatory Bodies Strict environmental regulations control the discharge of drill cuttings, with a primary focus on marine ecosystem protection. The Oslo-Paris (OSPAR) Convention sets the most restrictive standards for offshore activities in the North Sea and North-East Atlantic. Since 2001, OSPAR has prohibited offshore discharge of cuttings contaminated by oil-based and synthetic-based fluids unless residual oil is below 1% by dry weight. In 2012, OSPAR added stringent requirements for sediment monitoring and hydrocarbon reporting at drilling sites to support benthic ecosystem recovery. Other frameworks, including the EPA Effluent Guidelines (USA) (US Environmental Protection Agency (EPA) ( 2024 )), Barcelona Convention (Mediterranean), and London Protocol, regulate discharge limits and treatment methods, but OSPAR enforces the strictest, most comprehensive control of offshore discharge practices. In onshore operations, particularly in the UK, the Environmental Agency has issued sector-specific guidance that sets out detailed requirements for the management, treatment, and disposal of drill cuttings and associated wastes from oil and gas activities (Environmental Agency 2015 ). Industry guidance documents also emphasise the need to manage drilling fluids and associated health and environmental risks through a structured risk-management framework, particularly in offshore operations (IPIECA 2009 ). Drill cuttings Volume Today, oil and gas production as the world's primary energy source remains a crucial focus for production companies. Accessing oil and gas reservoirs at various depths is associated with producing a large volume of drilling cuttings, which are often contaminated due to the addition of organic and/or inorganic chemicals to the drilling fluid. This also happens while drilling in oil and gas reservoirs. These polluted drilling cuttings can cause significant environmental and public health issues and cannot be discharged into the environment without treatment. The studies show that the returned drilling fluids contain heavy metals like nickel, mercury, cadmium, chromium, copper, and lead. These elements are associated with chronic diseases, including cancer (Antia et al. 2022 ). Sustainable reservoir and production engineering practices increasingly require that drilling waste management be integrated into overall field development planning, rather than treated as an isolated downstream activity (Majid 2022 ). The transport and settling behaviour of drill cuttings in drilling fluids strongly affects surface solids control efficiency and the volume of cuttings requiring treatment, as highlighted by recent work on settling velocity and hydrodynamics of cuttings in complex mud systems (Agwu et al. 2018 ). The drilling fluid system is one of the main parts of the drilling operation and is the heart of the drilling operation. Figure 1 (Tabatabaei et al. 2022) shows a schematic of the drilling fluid circulation system. Drilling fluid can undertake more than 15 critical functions depending on different situations, from providing the necessary pressure to control formation pressures and overburdens, cooling and lubricating the drill bit and drill string, carrying cuttings to the surface, achieving geological information, etc. Diesel or chemical additives are usually used to impart lubricating properties to the mud. These additives are often derived from oil. The amount of this diesel used is proportional to the need, ranging from 1 to 3 percent of the volume of the drilling mud. On the other hand, adding other chemical additives and polymers makes the drilling cuttings sufficiently contaminated that they cannot be disposed of on land or sea without treatment. Various methods have been proposed and implemented for treating drill cuttings, each with its advantages and disadvantages. Treatment methods include land spreading, land farming, bioremediation, reinjection, fixation with agents like cement, thermal, etc. Ilinykh et al. ( 2023 ) developed a life cycle assessment (LCA) of drilling waste management methods in Russia. They compared land spraying, disposal, solidification, and reinjection. The results illustrate that solidification has the highest impact due to cement and lime consumption, while reinjection has the lowest environmental impact. In sensitive environments, especially marine environments, the methods above have not been able to reduce the contamination levels of drilling cuttings below global standards. As a result, specialists have always been looking for new methods to treat contaminated drill cuttings. One of these methods is pyrolysis, which involves the absorption or separation of contaminants from the surface of the drill cuttings by heating them. This method has gained attention in recent years. In the pyrolysis method, researchers have compared the use of conventional heat sources, such as electrical or microwave energy, multiple times. In all these studies, the superiority of microwave techniques over other thermal methods has been proven (Beneroso et al. 2015 ; Lu et al. 2012 ; Hossain et al. 2011 ; Shang et al. 2006 ; Robinson et al. 2008 b; Shang et al. 2007 ). The main reason for this result is the selective and volumetric heating provided by microwave methods. In all previous and current methods of treating drill cuttings, the treatment capacity has always been a challenge, particularly when drilling the upper sections of the well (top holes), where a large volume of drill cuttings, along with the returning drilling fluid, is discharged onto the shale shaker screens. Eq. 1 , adapted from standard drilling engineering practice, shows how much cutting is produced during drilling as a function of borehole geometry, porosity, washout, and penetration rate (Bourgoyne et al. 1986 ). $$\:Vc=\frac{\left(1-{\varnothing}\right)\text{*}{(D+W)}^{2}*ROP}{1029.4}$$ 1 Where, Vc is the volume of cutting in bbl/hr. Ø is formation porosity (%). D is the wellbore diameter in inches. W is wellbore washout in inches ROP is the rate of penetration in feet per hour. In other words, the production rate of drill cuttings in the upper sections of the well is much higher than their treatment rate. In onshore drilling, due to the availability of sufficient space, these drill cuttings are usually stored in constructed pits like coral, waste pits and tanks, where they are treated over time and eventually disposed of in landfills. Due to the lack of space in offshore drilling platforms, using a sufficient number of skips to store the drill cuttings is impossible. Therefore, there is a need to address this deficiency in the treatment methods and design the methods and related equipment to allow the produced cuttings to be treated quickly onsite and discharged into the sea. Alternative solutions for handling offshore cuttings usually come with secondary pollution and require significant time and cost. For example, transporting the drill cuttings to shore (skip and ship) for treatment and disposal involves challenges such as high transportation costs, the long distance between the drilling platform and the shore, and air and noise pollution caused by ship traffic. Additionally, disposing of drill cuttings onshore often leads to soil and groundwater contamination. Advanced Thermal Processor (ATP) ATP uses microwave and Infrared energy to remove oil contamination from drill cuttings. This processor is a fully integrated solution for treating drill cuttings without adversely affecting the land or marine environment. The technology is based on the advanced simultaneous use of multiple electromagnetic frequencies and a unique phase separation drum. This maximises heat and mass transfer within the system, reducing plant size, material holdup, and operating costs. In addition, the low-intensity thermal regimes allow oil to be recovered without degradation. Infrared radiation provides surface heating, which can be effective in applications where rapid surface drying or decontamination is required. Some of the benefits of the ATP are: Processor treats a wide range of feedstocks, including OBM, SBM and WBM, with crude and low and high water/oil contents Using a rotating drum to minimise the cutting residence time Treat cuttings continuously Energy efficient in comparison to other methods Treats drill cuttings to less than 1% oil on cuttings No quenching is required after processing. Creates clean oil and water streams Low-intensity thermal regimes, no oil degradation The processor system uses microwave and infrared energy to remove the oil contamination in drill cuttings arising from water or oil-based mud operations. The microwave energy specifically targets the moisture in the drill cuttings and the subsequent rapid evaporation, which removes the contaminating oil by the mechanism of steam stripping. Because of the manner of the energy transfer, the system operates at lower energy and temperature than conventional thermal processes. The throughput of the system depends on the available energy of the system and the moisture content of the received feed. Evaporation of moisture consumes a significant portion of the microwave and infrared energy. Therefore, preconditioning the feed by removing excess water mechanically increases the system's effective throughput. The solids processor consists of the following main components: Enclosed conveying system for controlled feed Industrial standard microwave generators Infrared heated reactor chamber Enclosed solids discharge system Inert purge safety system Condenser system to separate oil and water Fully integrated PLC control system Materials and Methods Process Overview Solids Treatment The waste stream is fed into the processor's primary feed hopper. The waste is continuously fed from the hopper at the required rate, via an enclosed screw conveyor, to the processor. The rotating processor efficiently exposes the waste to powerful microwave and infrared energy as it passes through it. Process conditions, such as residence time and energy input, are optimally selected to ensure complete treatment of the specific waste stream. All vapours and gases released during processing are swiftly extracted from the reaction chamber by a high-efficiency fan and directed to a dedicated condensate and gas clean-up system. The fan’s suction is precisely regulated to maintain optimal operating conditions, even when feedstock composition varies. Treated solids are discharged from the processor through isolation valves and conveyed via an enclosed screw conveyor to the discharge line. As the solids exit at relatively low temperatures, high-volume water quenching is not required. An inert atmosphere is maintained inside the processor, achieved initially by purging with nitrogen gas and steam generated in situ during operation. The processor is sealed to prevent any air ingress during operation. Instrumentation monitors the system for flammability, and in the event of an alarm condition, the processor is automatically purged with nitrogen gas and the system is shut down. Oil and Water Handling The oil/water vapour handling system (Fig. 2 ) separates entrained solid particles from the vaporised oil and water stream through a series of separation processes. The system produces water with an oil content of 0–15 ppm and recovers oil suitable for reuse in new drilling fluid formulations. In this system, energy is applied directly to the water and oil components within the feed material, enabling rapid and efficient removal with minimal heat transfer to the inert solids in the drill cuttings. As a result, all of the applied energy is effectively used to extract the contaminants. The processor features a mechanically simple design with few moving parts. It operates gently, using slow rotation to achieve material movement and mixing, resulting in minimal wear, low maintenance requirements, and reduced repair needs. Feed system and design criteria The contaminated cuttings are received from the storage tank. A decanting centrifuge is used to remove the free water, lowering the moisture content in order to maximize the throughput of the system. Any sludge generated during the natural process is reintegrated into the feed stream by metering it, along with dewasstered drill cuttings, into a continuous paddle blender. This ensures a uniform and consistent mixture. The feed is mechanically conveyed into the hopper of the ATP unit. The level in the hopper is maintained to provide an airlock. At the interior base of the hopper, a hydraulically operated sliding frame reciprocates continuously, thereby providing a continuous feed to the offtake screw. The sliding frame design is key to the material handling of the highly variable flow characteristics of the drill cuttings. The action of the sliding frame keeps the exposed flights of the offtake screw conveyor full, thereby providing accurate volumetric proportioning. The variable pitch screw drives material into the processor. As the flight length increases, the feed breaks up before entry into the ATP processor. Our challenge has been to design a feed unit that can ultimately accept either pump or conveyor technology, depending on the moisture content. The feed system must be flexible enough to operate in a number of density ranges whilst generating a seal to minimise oxygen leakage into the processor. The unit needs to operate safely in extreme temperature conditions situated in an ATEX zone two area. One of the design concerns was the feed characteristics. The contaminated cutting can vary both in moisture/oil content and flow characteristics, and therefore, a unit has been selected that can handle a wide range of materials. The sliding frame of the hopper is key to the design of the unit in that it constantly agitates and mobilises the material and allows a constant volumetric flow into the processor. ATP Drum The processor consists of a rotating drum, which is inclined slightly from horizontal. The cuttings travel at a speed which is a function of the circumferential velocity. The cuttings are subjected to both microwave energy and infrared-sourced thermal energy for 15 minutes. During this time, the water and oil are driven off the cuttings into the vapour phase. The ATP drum is housed within a sealed canopy in which the infrared heaters are located. The heaters are situated along the complete length and circumference of the drum in order to distribute the energy evenly. The canopy is filled with nitrogen controlled at a slightly higher pressure to both the atmosphere and the processing chamber. This ensures that any leakage across the drum seal will be nitrogen leaking inwards, again avoiding any chance of air ingress. Discharge system Following processing, the drill cuttings are stripped of moisture and oil, resulting in a dry, powdery solid (Fig. 3 ) that is easily conveyed. The treated material exits the processor via an inclined screw conveyor and passes through a rotary valve, which serves as an airlock at the discharge end of the system. The solids can then be safely discharged overboard. To prevent airborne dust emissions, a water mist system is employed. Vapour handling The ATP process incorporates a recirculating gas stream that acts as a carrier gas in the process. As the stream and oil vapour are produced from the bed, the carrier gas transports the condensable to the oil/water collection system. Vapour exits the ATP processor at the discharge end and first passes through a gas scrubber to remove any entrained solid particles. It then enters the condensate unit, where heat is removed from the stream, causing the oil and water to condense out of the vapour phase. The resulting condensate is directed to an oil/water plate separator for oil recovery. The remaining gas flows to a loop fan that drives carrier gas recirculation, after which it is reheated and returned to the ATP processor. The condensed water is utilised in the discharge mist system to control dust emissions. A desktop device was initially designed and built in the first phase in our lab. In the second phase, modifications were made, and a prototype (Fig. 4 ) device was developed. In this study, tests were conducted using the prototype device and the results were analysed. Safety and Inert Atmosphere Control The drum is enclosed within a sealed canopy filled with nitrogen at a slightly higher pressure than the processing chamber. This prevents air leakage into the system, ensuring safe operation in the ATEX Zone 2 environment. Additional safety measures include continuous monitoring of oxygen levels and redundant nitrogen supply to maintain an inert atmosphere. Post-Processing and Waste Management Following processing, the treated drill cuttings are converted into a dry, powder-like solid, which is easily conveyed via an inclined screw conveyor. The treated material passes through an airlock valve before final disposal. A water mist system is employed to suppress dust emissions. Energy Efficiency Considerations Due to the high energy demand associated with moisture evaporation, pre-conditioning of the feed is essential. Mechanical dewatering using a centrifuge reduces excess water, thereby increasing the system’s effective throughput. Additionally, energy recovery mechanisms, such as heat exchangers, can be incorporated to optimize thermal efficiency. Results and discussion Offshore Project - a Case Study This study was carried out on water-based drill cuttings contaminated with sour crude oil. The samples were collected from an offshore drilling rig in the Middle East. The samples were processed using our prototype. The objective of the project was to develop a full-scale, rig-based ATP system, with the prototype results used to define the operating envelope and required processing conditions. The design of the full-scale ATP and its feed system will be presented in a separate article. The current paper focuses on the results obtained from processing the samples using the ATP prototype unit at our lab. The prototype unit uses microwave and infrared energy to remove the oil contamination in water-based drill cuttings. Six samples of water-based drill cuttings contaminated with sour crude were received from an offshore field. After laboratory characterisation of these samples, they were processed in the ATP prototype in two batches. The treated drill cuttings contained less than 1% oil on cuttings, confirming that significant oil removal had been achieved. The recovered oil exhibited high-boiling fractions, as expected from crude oil contamination. The samples were processed using microwave-induced oil stripping. During the initial phase, the feed rate and bed depth were adjusted to maximise microwave energy absorption. Across six samples, absorption efficiency was high, with negligible reflected power recorded. Test runs were carried out under standard water-based mud (WBM) conditions, targeting a solid discharge temperature of 60°C to 100°C. The discharged solids were left to air-cool, without the use of water quenching. Table 1 Oil, water, and hydrocarbon content of water-based drill cuttings before and after treatment using the ATP prototype unit. Oil Content (% W/W) Water Content (% W/W) Oil Removal Efficiency TPH (mg/kg) TOG (%) Sample ID Before After Before After (%) Before After Before After 1 5.7 0.15 17.2 0 97.37 15067 590 4.62 0.18 2 5.3 0.15 17.5 0.15 97.17 14119 564 4.18 0.14 3 5.2 0.17 17.8 0.075 96.73 12733 490 3.87 0.11 4 5.9 0.14 16.8 0.1 97.63 17340 681 5.5 0.22 5 6.3 0.14 15.3 0.2 97.78 19740 731 6 0.25 6 4.4 0.22 24 0.35 95.00 9500 205 3.57 0.04 Total Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) are critical parameters used to evaluate hydrocarbon contamination in drill cuttings. TPH quantifies the total concentration of petroleum-derived hydrocarbons, while TOG encompasses both petroleum hydrocarbons and other solvent-extractable organic compounds such as animal or vegetable oils. In this study, TPH and TOG were measured using standard gravimetric and infrared spectrophotometric methods following solvent extraction, in accordance with recognised environmental testing protocols. Reducing TPH and TOG levels is a key objective, as it directly influences environmental safety, regulatory compliance, and the viability of waste management strategies for treated cuttings. High removal efficiencies achieved through the microwave/infrared treatment process demonstrate its effectiveness in producing near-inert solid waste, thereby supporting safe discharge or potential reuse of the treated material. Table 1 illustrates the removal efficiency for oil content, water content, TPH, and TOG across all samples. Key observations include: Oil Content: Removal efficiency ranges from ~ 95% to ~ 97.8%, with Sample 5 showing the highest efficiency. Water Content: Removal efficiency is consistently high, with most samples achieving > 99% removal. Sample 6, however, shows slightly lower efficiency (~ 98.5%) due to its higher initial water content. TPH: Removal efficiency ranges from ~ 96% to ~ 98%, with Sample 6 showing the lowest efficiency (~ 95%). TOG: Removal efficiency is consistently high, with all samples achieving > 96% removal. The bar chart (Fig. 5 ) underscores the versatility of the treatment process in handling multiple contaminants simultaneously. This is a significant advantage over traditional methods, which often require separate treatment steps for oil, water, and solids. The ability to achieve high removal efficiencies for all contaminants in a single process step enhances the economic and environmental feasibility of the technology. Oil Removal Efficiency vs. Initial Water Content The graph of oil removal efficiency vs. initial water content (Fig. 6 ) shows a clear trend: as the initial water content increases, the oil removal efficiency decreases. This is particularly evident in sample 6, which has the highest initial water content (24% w/w) and the lowest oil removal efficiency (~ 95%). On the other hand, samples with lower initial water content (e.g., Sample 5 with 15.3% w/w) demonstrate higher oil removal efficiency (~ 97.8%). The inverse relationship between oil removal efficiency and initial water content can be attributed to the competition for thermal energy during the microwave/infrared treatment process. Water, being a polar molecule, absorbs microwave energy more efficiently than oil. As a result, in samples with higher water content, a significant portion of the energy is consumed in heating and evaporating water, leaving less energy available for breaking down and removing oil. Additionally, the presence of water can create a barrier effect, where water molecules surround oil droplets, making it more difficult for the thermal energy to reach and volatilise the oil. Oil Removal Efficiency vs. Initial Oil + Water Content This section examines the relationship between oil removal efficiency and the total initial fluid load (combined oil and water content-Fig. 7) present in drill cuttings. The plotted data suggest a subtle inverse trend, samples with higher fluid content (> 23% w/w) appear to show slightly lower oil removal efficiency compared to those with less fluid content. For instance, the sample with 28.4% oil + water content achieved only 95.0% removal efficiency, while samples with ~ 21.6–22.7% fluid content reached removal efficiencies near 97.6–97.8%. This behavior can be explained by fluid dynamics during thermal desorption. According to prior studies (e.g., Noor et al. 2018 ), excess water can form an insulating vapor layer around oil droplets under rapid heating, hindering direct thermal contact between the droplet surface and the heat source. This phenomenon, commonly referred to as the Leidenfrost effect, can reduce desorption efficiency, especially in fine-textured materials like drill cuttings where oil droplets are embedded within a matrix. The current trend, while based on six samples, aligns with thermodynamic expectations and highlights the potential benefit of pre-drying or moisture control prior to thermal treatment. These findings support the optimization of operating parameters based on fluid content to maximise oil removal performance. The process incorporates a gas recirculation system to transport steam and oil vapours to an oil-water separation unit. The vapour stream first passes through a gas scrubber to remove entrained solid particles before entering a condenser. Here, heat is extracted, allowing oil and water to be separated and recovered. The remaining gas is then recirculated back into the processor, enhancing energy efficiency and minimising emissions. Thermogravimetric Analysis (TGA) of Treated Drill Cuttings TGA is a widely accepted technique used to monitor the weight change of materials in response to increasing temperature. In the context of drill cuttings remediation, TGA provides critical insights into the removal behavior of volatile components, such as hydrocarbons and water, and helps evaluate the energy efficiency and thermal footprint of the treatment technology. For sample 1, with an initial oil content of 5.7% w/w and water content of 17.2% w/w, the TGA curve shows a dominant mass loss of 21.17% at just 106°C. This strongly indicates the removal of surface-bound water and light volatile fractions at very low temperatures. The fact that nearly the entire oil and water content of the sample is removed below 110°C demonstrates that the ATP can operate effectively under low-temperature conditions. This early-stage vaporisation confirms the low energy demand and high thermal efficiency of the ATP process, especially when compared to traditional high-temperature methods like incineration or friction-based desorption. Beyond this initial phase, the TGA (Fig. 8 ) trace indicates only minimal additional mass loss: 3.35% at 275°C, 2.24% at 413°C, and 31.96% at 720°C, suggesting that the remaining matrix consists mostly of inorganic or thermally stable residuals. Importantly, the near-absence of volatiles below 400°C after ATP processing confirms that contaminants such as oil and water have been nearly completely eliminated, aligning with regulatory standards such as OSPAR’s < 1% oil-on-cuttings threshold. This thermal profile is not only a validation of treatment completeness but also a demonstration of safe, low-discharge temperatures and environmentally compliant residue behavior. In ATP, microwave and infrared heating penetrate the matrix volumetrically, rapidly driving off moisture and releasing embedded oil droplets without overheating or structural degradation. Overall, TGA confirms that ATP achieves thorough decontamination through precisely controlled, low-temperature desorption, with minimal energy input and a residue that is both stable and environmentally acceptable. Conclusion The ATP offers a significant advancement in the sustainable treatment of oil-contaminated drill cuttings. Through the integration of microwave and infrared heating within a sealed, nitrogen-controlled chamber, ATP achieves effective decontamination at lower temperatures than conventional thermal technologies. This minimises energy demand and discharge temperature, supporting cleaner offshore operations. The experimental findings confirm that ATP consistently removes oil, water, TPH, and TOGs with high efficiency, even when initial contaminant levels vary. Across all tested samples, the system consistently delivered oil removal efficiencies greater than 95%, with some reaching up to 97.8%. TGA further validated the treatment mechanism, showing that over 21% of sample weight, corresponding to oil and water, was vaporised at just 106°C. These results confirm ATP’s ability to remove the majority of volatiles under mild thermal conditions, reducing operational risk and energy consumption. The observed relationships between initial oil/water content and removal efficiency provide valuable insight into process optimisation, while the system’s ability to perform consistently across variable contamination levels confirms its industrial potential. Unique design features, such as continuous feed, a rotating drum, and low-emission processing, make ATP a technically robust alternative to skip-and-ship and other energy-intensive treatment options. This work supports broader industry efforts toward environmentally responsible waste management. Future development may focus on upscaling, energy integration, and extended economic evaluation to maximise the technology’s potential in offshore and remote settings. Declarations Competing Interests The authors declare that they have no competing financial or non-financial interests that are directly or indirectly related to the work submitted for publication. Ethical Approval This is not applicable. Consent to Participate This is not applicable. Consent to Publish This is not applicable. Funding This research received no external funding. Data Availability The datasets analysed during the current study are available from the corresponding author on reasonable request. CRediT authorship contribution statement Roohollah Babaei-Mahani1: Conceptualization, Writing – original draft, Supervision. Ali Fereidounpour: Writing - Review & Editing, Visualization . Yinghe He: Writing - Review & Editing. Peter Scholes: Methodology, Writing - Review & Editing. Acknowledgements Not applicable References Agwu OE, Akpabio JU, Alabi SB (2018) Settling velocity of drill cuttings in drilling fluids: A review of experimental, numerical simulations and artificial intelligence studies. Powder Technol 339:728–746. https://doi.org/10.1016/j.powtec.2018.08.048 Antia M, Ezejiofor AN, Obasi CN, Orisakwe OE (2022) Environmental and public health effects of spent drilling fluid: An updated systematic review. J Hazard Mater Adv 7:100120. https://doi.org/10.1016/j.hazadv.2022.100120 Ball AS, Stewart RJ, Schliephake K (2012) A review of the current options for the treatment and safe disposal of drill cuttings. Waste Manag Res 30(5):457–473. https://doi.org/10.1177/0734242X12444897 Beneroso D, Monti T, Kostas ET, Robinson JP (2015) Microwave pyrolysis of biomass for bio-oil production: Scalable processing concepts. Chem Eng J 279:251–263. https://doi.org/10.1016/j.cej.2015.05.019 Bourgoyne AT, Millheim KK, Chenevert ME, Young FS (1986) Applied drilling engineering. Society of Petroleum Engineers Celik S, Kose E, Çelen S, Akin G, Akyıldız A (2019) Drying of drilling sludge: Conventional and microwave drying. Hittite J Sci Eng 6:119–122. https://doi.org/10.17350/HJSE19030000136 Environmental Agency UK (2015) Onshore oil & gas sector guidance. https://assets.publishing.service.gov.uk/media/5a818a3f40f0b62302697dc3/Onshore_oil_and_gas_sector_guidance.pdf Hossain MK, Strezov V, Chan KY, Ziolkowski A, Nelson PF (2011) Influence of pyrolysis temperature on production and nutrient properties of wastewater sludge biochar. J Environ Manage 92(1):223–228. https://doi.org/10.1016/j.jenvman.2010.09.008 Hou Q, Liu B, Liu X, Guo Y (2018) Simulation and experimental study on the motion characteristics of drill cuttings in deviated wells. J Nat Gas Sci Eng 54:1–12. https://doi.org/10.1016/j.jngse.2018.03.002 Ilinykh G, Fellner J, Sliusar N, Korotaev V (2023) A life cycle assessment of drilling waste management: A case study of oil and gas condensate field in the north of western Siberia, Russia. Sustainable Environ Res 33(1):1–12. https://doi.org/10.1186/s42834-023-00178-7 IPIECA (2009) Drilling fluids and health risk management: A guide for drilling personnel, managers, and health professionals in the oil and gas industry. IPIECA Junior I, Pereira M, Santos J, Duarte CR, Ataíde C, Panisset C (2015) Microwave remediation of oil well drill cuttings. J Petrol Sci Eng 134:23–31. https://doi.org/10.1016/j.petrol.2015.07.022 Liu H, Wang J, Zhang Y, Xu Q, Li G (2023) Thermal treatment of hydrocarbon-impacted soils: A review of technology innovation for sustainable remediation. J Environ Manage 325:116632 Lu L, Leung DYC, Wang H, Huang H (2012) An overview of bio-oil from the pyrolysis of biomass. Appl Energy 99:326–332. https://doi.org/10.1016/j.apenergy.2012.05.042 Majid T (2022) Sustainable natural gas reservoir and production engineering, vol 1. Elsevier Mota ACS, Santos JM, Pereira MS, Ataíde CH Kinetics of batch microwave drying of drill cuttings contaminated with an olefin-based fluid. AADE Fluids Technical Conference and, Exhibition (2018) AADE-18-FTCE-099. https://www.aade.org/application/files/9015/7131/7045/AADE-18-FTCE-099_-_Mota.pdf Mueller F, Andrade D, Massam K (2013) Optimizing drilling waste treatment to meet discharge criteria. Soc Petroleum Eng. https://doi.org/10.2118/163467-MS Noor I, Ali N, Khan N, Mehmood M (2018) Thermophysical properties and heating behavior of oily sludge under microwave irradiation. J Therm Anal Calorim 132(2):893–901. https://doi.org/10.1007/s10973-017-6842-3 Pereira MS, Panisset CM, de Martins Á, Sá AL, de Barrozo CHM, M. A., Ataíde CH (2014) Microwave treatment of drilled cuttings contaminated by synthetic drilling fluid. Sep Purif Technol 124:142–149. https://doi.org/10.1016/j.seppur.2014.03.032 Robinson JP, Kingman SW, Snape CE, Shang H (2008) Advanced microwave processing of drill cuttings: Design, simulation, and evaluation. Proceedings of the SPE/IADC Drilling Conference, SPE-112041-MS. https://doi.org/10.2118/112041-MS Robinson JP, Kingman SW, Snape CE, Bradshaw SM, Bradley MSA, Shang H, Barranco R (2010) Scale-up and design of a continuous microwave treatment system for the processing of oil-contaminated drill cuttings. Chem Eng Res Des 88(11):146–154. https://doi.org/10.1016/j.cherd.2010.01.012 Rossi LM (2016) Thermal treatment of drill cuttings (Master’s thesis). University of Stavanger Santos J, Pereira M, Junior I, Pena M, Ataíde C (2014) Microwave drying of drilled cuttings in the context of waste disposal and drilling fluid recovery. Energy Technol 2. https://doi.org/10.1002/ente.201402053 Semple KT, Reid BJ, Fermor TR (2003) Impact of composting strategies on the fate of polyaromatic hydrocarbons in soil. Environ Pollut 124(3):317–329 Shang H, Snape CE, Kingman SW, Robinson JP (2006) Microwave treatment of oil-contaminated North Sea drill cuttings in a high power multimode cavity. Sep Purif Technol 49(3):84–90. https://doi.org/10.1016/j.seppur.2005.08.007 Shang H, Snape CE, Kingman SW, Robinson JP (2007) A pilot-scale study on microwave remediation of oil-based drill cuttings. J Hazard Mater 145(1–2):234–240. https://doi.org/10.1016/j.jhazmat.2006.11.022 US Environmental Protection Agency (EPA) (2024) TENORM: Oil and gas production wastes. https://www.epa.gov/radiation/tenorm-oil-and-gas-production-wastes Veil JA, Dusseault MB, Gray DH, McMillen SJ, Caudle DD (1996) Evaluation of disposal options for drilling wastes. Argonne National Laboratory, US Department of Energy Yan P, Lu M, Guan Y, Zhang W, Zhang Z (2011) Remediation of oil-based drill cuttings through a biosurfactant-based washing followed by a biodegradation treatment. Bioresour Technol 102(22):10252–10259. https://doi.org/10.1016/j.biortech.2011.08.074 Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major Revision 23 Mar, 2026 Reviewers agreed at journal 24 Feb, 2026 Reviewers invited by journal 24 Feb, 2026 Editor invited by journal 12 Feb, 2026 Editor assigned by journal 04 Feb, 2026 First submitted to journal 03 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8732040","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":596510861,"identity":"0878fa22-6adf-4710-9d94-e9f75a55af62","order_by":0,"name":"Roohollah Babaei-Mahani","email":"data:image/png;base64,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","orcid":"","institution":"Brunel University London","correspondingAuthor":true,"prefix":"","firstName":"Roohollah","middleName":"","lastName":"Babaei-Mahani","suffix":""},{"id":596510862,"identity":"16f8dd6f-6218-4c3a-9fb9-7fef22521fcb","order_by":1,"name":"Ali Fereidounpour","email":"","orcid":"","institution":"Brunel University London","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"","lastName":"Fereidounpour","suffix":""},{"id":596510863,"identity":"beec62fc-8e04-434a-a519-939d6aa8ce83","order_by":2,"name":"Yinghe He","email":"","orcid":"","institution":"Brunel University London","correspondingAuthor":false,"prefix":"","firstName":"Yinghe","middleName":"","lastName":"He","suffix":""},{"id":596510864,"identity":"364f98fd-98e9-4f8e-97d8-9e86dde40ce5","order_by":3,"name":"Peter Scholes","email":"","orcid":"","institution":"Rotawave Scotland LTD","correspondingAuthor":false,"prefix":"","firstName":"Peter","middleName":"","lastName":"Scholes","suffix":""}],"badges":[],"createdAt":"2026-01-29 13:20:03","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8732040/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8732040/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103530565,"identity":"0aee0e99-7e9c-4d58-a974-52aa22ddd984","added_by":"auto","created_at":"2026-02-26 16:55:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":139583,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of a drilling fluid circulation system in rotary drilling operations.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/b731f7c13ddce3b57d7021ba.png"},{"id":103530560,"identity":"b6f1c62f-5468-4386-a8c6-8444ff16c90d","added_by":"auto","created_at":"2026-02-26 16:55:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":37840,"visible":true,"origin":"","legend":"\u003cp\u003eProcess flow diagram of the oil and water vapour handling and separation system for contaminated drill cuttings.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/aac260d19d2737aa3be7f0c6.png"},{"id":103530558,"identity":"7d6e746a-4a0b-4aa1-8aa1-b9812b86187d","added_by":"auto","created_at":"2026-02-26 16:55:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1333367,"visible":true,"origin":"","legend":"\u003cp\u003eVisual comparison of drill cuttings before and after treatment in the discharge system.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/824cc85dc8406c45bf6f1a64.png"},{"id":103530556,"identity":"9df3a81f-1752-4e7b-a322-d1e6d0781b88","added_by":"auto","created_at":"2026-02-26 16:55:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":107836,"visible":true,"origin":"","legend":"\u003cp\u003ePrototype ATP unit used for vapour handling and condensate recovery in this study.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/994c4b811e007b92938fdf74.png"},{"id":103530552,"identity":"c806133d-e002-49aa-90dd-39c33970d3ba","added_by":"auto","created_at":"2026-02-26 16:55:47","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":311895,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of oil content in water-based drill cuttings before and after treatment using the ATP prototype unit.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/2b4bc0bc9aea999cc9958a1f.png"},{"id":103530559,"identity":"d564e6c0-f975-4d1b-b75e-11981db88a3b","added_by":"auto","created_at":"2026-02-26 16:55:50","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":174717,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between initial water content and oil removal efficiency for water-based drill cuttings treated using the ATP prototype.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/8bb7488849690aa158cab8f5.png"},{"id":103530554,"identity":"d928e9d2-ea4d-478d-9294-3df2ab0d6ed5","added_by":"auto","created_at":"2026-02-26 16:55:48","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":269855,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between initial total fluid content (oil + water) and oil removal efficiency for water-based drill cuttings treated using the ATP prototype.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/9a952fd105273ccca89b3515.png"},{"id":103530557,"identity":"015fc3d9-5a6f-4e07-b726-948e010ebcc8","added_by":"auto","created_at":"2026-02-26 16:55:50","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":108903,"visible":true,"origin":"","legend":"\u003cp\u003eTGA curve of ATP-treated drill cuttings (Sample 1).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/95960f7f57a47c4b311fee81.png"},{"id":104398211,"identity":"c1ad94e1-09f5-4b80-855c-deb5957133e4","added_by":"auto","created_at":"2026-03-11 12:00:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3246415,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8732040/v1/30a49d3b-39e2-4b9a-998a-110a3d59f849.pdf"}],"financialInterests":"","formattedTitle":"Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings","fulltext":[{"header":"Highlights","content":"\u003cp\u003e\u0026bull; Continuous hybrid microwave-infrared thermal desorption of drill cuttings.\u003c/p\u003e\u003cp\u003e\u0026bull; Oil removal efficiencies\u0026thinsp;\u0026gt;\u0026thinsp;95% with final oil‑on‑cuttings\u0026thinsp;\u0026lt;\u0026thinsp;1 wt.%.\u003c/p\u003e\u003cp\u003e\u0026bull; Low‑temperature contaminant removal confirmed by TGA analysis.\u003c/p\u003e\u003cp\u003e\u0026bull; Applicable to offshore drilling waste management.\u003c/p\u003e"},{"header":"Introduction","content":"\n\u003ch3\u003eBackground and context\u003c/h3\u003e\n\u003cp\u003eThe volume of drill cuttings waste generated during oil and gas exploration and production can exceed 5,000 cubic meters per well, depending on several critical factors (Biltayib et al. 2016). Drill cuttings are pieces of rock brought to the surface during drilling operations by the action of drilling bits. The physical and chemical properties of drill cuttings depend on the type of drill bits, drilling mud, penetration rate, formation types, and additives used.\u003c/p\u003e \u003cp\u003eProper management of drill cuttings waste is essential to mitigate environmental impacts and comply with national and international regulations. The factors influencing drilling waste generation include the type of formation, well depth, borehole diameter, drilling fluid selection, solid control equipment, formation porosity, and borehole washout. Harder formations typically yield fewer cuttings than softer formations. Deeper wells and larger boreholes contribute to increased volumes of cuttings. The type of drilling fluid, water-based, oil-based, or synthetic-based, affects the volume and the environmental compatibility of the cuttings.\u003c/p\u003e \u003cp\u003eFormation porosity also plays an important role in the volume of cuttings produced. Higher porosity formations generate fewer cuttings. Another critical factor is borehole washout, which occurs when the actual size of the wellbore is larger than the drill bit size due to the collapse or erosion of the formation during drilling. Washout is particularly prevalent in loose or weak formations, such as shale or unconsolidated sands, which are prone to erosion. This results in increased volumes of cuttings. Larger washout percentages directly correspond to greater waste volumes, making this a key consideration in waste management strategies.\u003c/p\u003e \u003cp\u003eVarious methods exist for disposal and management of drill cuttings; each presents specific challenges. Landfarming (Ball et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) spreads cuttings over land, mixing them with soil to promote bioremediation. This technique is most suitable for waste derived from water-based muds, as oil-based contamination can pose significant environmental harm. Injection of cuttings into subsurface formations (veil et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1996\u003c/span\u003e) offers secure containment, as long as both specialized equipment and suitable geological zones are available. However, this method essentially transfers the pollution from the surface to deeper geological layers, raising concerns about long-term environmental impacts. Biodegradation (Semple et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) employs microorganisms to break down hydrocarbons, but it proceeds more slowly and with less effectiveness when dealing with heavily contaminated or resistant materials such as high-molecular-weight aromatics, tars, or weathered oil residues. For oil-based drill cuttings, combining surfactant-based washing with subsequent biodegradation has been shown to significantly reduce residual hydrocarbons, illustrating the potential of integrated biological approaches (Yan et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Solidification immobilizes contaminants, but cannot fully prevent leaching and may itself introduce further pollutants, especially under changing environmental conditions (Negata, 2003), such as acid rain, fluctuations in pH, or cyclic wetting and drying. Incineration at high temperatures can effectively neutralize many hazardous contaminants and greatly reduce waste volume, but it is energy-intensive and must be accompanied by stringent control of air emissions to avoid the release of toxic by-products. These observations are consistent with broader reviews of thermal treatment of hydrocarbon-impacted soils, which emphasise the trade-off between temperature, residence time, and environmental performance (Liu et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Field experience has shown that optimising drilling waste treatment trains and matching technologies to local discharge criteria is essential for achieving regulatory compliance at acceptable cost (Mueller et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRecent developments have explored microwave technology as a treatment method for drill cuttings. The advantage of microwave processes is rapid, localized heating, which can decompose hydrocarbons and reduce contamination (Pereira et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Most published research, however, concerns experimental or batch-scale tests. To date, continuous microwave systems have not matched the required capacity for real-world drilling rates (Mota et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The scale-up and design of continuous microwave systems for oil-contaminated drill cuttings have been investigated, highlighting both the potential of this technology and the engineering challenges associated with continuous operation (Robinson et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). For instance, prototype units achieve treatment rates well below those produced during active drilling. Further optimization for continuous operation and scale-up is needed to realize industrial application.\u003c/p\u003e \u003cp\u003eOverall, current management techniques for drill cuttings suffer from scalability or environmental trade-offs. This study introduces a novel processing method, aiming to address current limitations with improved efficiency and sustainability.\u003c/p\u003e"},{"header":"Literature Review","content":"\u003cp\u003eMicrowave technology has emerged as a highly effective method for treating drill cuttings contaminated with synthetic and oil-based drilling fluids. This technology leverages microwaves' unique ability to heat materials volumetrically, providing rapid and uniform heating that is not achievable with conventional thermal methods.\u003c/p\u003e \u003cp\u003ePereira et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) demonstrated that microwave radiation could reduce n-paraffin content in cuttings contaminated with non-aqueous fluids (NAFs) to below the discharge limit of 6.9% by mass, making it a viable option for on-site decontamination.\u003c/p\u003e \u003cp\u003eSimilarly, Mota et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) explored the kinetics of batch microwave drying of drill cuttings contaminated with an olefin-based fluid and achieved significant reductions in drying time and energy consumption, particularly at lower power settings. Their studies have shown that microwave heating promotes selective heating at the molecular level, providing advantages such as energy efficiency and shorter drying times. For instance, microwave drying technology allows the reuse of the recovered organic phase in the preparation of a new load of drilling fluid, as it does not alter the chemical composition of the fluid.\u003c/p\u003e \u003cp\u003eMicrowave heating produced more porous solid residues that enhanced heat and mass transfer during the treatment process, leading to greater mass loss and lower residual oil content in the treated cuttings (Celik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSeveral studies have compared microwave and infrared technologies to conventional thermal methods such as electric heating. Microwave heating has been shown to produce more porous solid residues, which enhance heat and mass transfer during the treatment process. This leads to greater mass loss and lower residual oil content in the treated cuttings (Junior et al. 2019). In addition to these studies, microwave drying of drilled cuttings has been shown to recover drilling fluid while reducing waste volume, further supporting the feasibility of microwave-based remediation (Santos 2014).\u003c/p\u003e \u003cp\u003eIn contrast, electric heating relies on the thermal conductivity of the material and the heat transfer efficiency in the system, which can be less effective for decontaminating drill cuttings. Previous work on the thermal treatment of drill cuttings has also identified scale-up, energy consumption, and off-gas handling as key design constraints for commercial systems (Rossi \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Additionally, the use of microwave technology has shown that it can promote the pyrolysis of petroleum hydrocarbons, making it more suitable for treating oil-based drilling cuttings (Hou et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMicrowave technology offers a promising solution for the treatment of drill cuttings contaminated with synthetic and oil-based fluids. Its ability to provide rapid, uniform heating with reduced energy consumption and environmental impact makes it a superior alternative to traditional thermal methods. However, challenges such as scaling up the technology for continuous processing need to be addressed to fully realise its potential in industrial applications.\u003c/p\u003e \u003cp\u003eFurther research into the optimization of process parameters and the design of continuous microwave treatment systems is necessary. The integration of microwave technology with existing oil and gas operations can significantly reduce the environmental footprint of drilling activities and provide a sustainable method for the remediation of drill cuttings.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eRegulatory Bodies\u003c/h2\u003e \u003cp\u003eStrict environmental regulations control the discharge of drill cuttings, with a primary focus on marine ecosystem protection. The Oslo-Paris (OSPAR) Convention sets the most restrictive standards for offshore activities in the North Sea and North-East Atlantic. Since 2001, OSPAR has prohibited offshore discharge of cuttings contaminated by oil-based and synthetic-based fluids unless residual oil is below 1% by dry weight. In 2012, OSPAR added stringent requirements for sediment monitoring and hydrocarbon reporting at drilling sites to support benthic ecosystem recovery. Other frameworks, including the EPA Effluent Guidelines (USA) (US Environmental Protection Agency (EPA) (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)), Barcelona Convention (Mediterranean), and London Protocol, regulate discharge limits and treatment methods, but OSPAR enforces the strictest, most comprehensive control of offshore discharge practices. In onshore operations, particularly in the UK, the Environmental Agency has issued sector-specific guidance that sets out detailed requirements for the management, treatment, and disposal of drill cuttings and associated wastes from oil and gas activities (Environmental Agency \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Industry guidance documents also emphasise the need to manage drilling fluids and associated health and environmental risks through a structured risk-management framework, particularly in offshore operations (IPIECA \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eDrill cuttings Volume\u003c/h3\u003e\n\u003cp\u003eToday, oil and gas production as the world's primary energy source remains a crucial focus for production companies. Accessing oil and gas reservoirs at various depths is associated with producing a large volume of drilling cuttings, which are often contaminated due to the addition of organic and/or inorganic chemicals to the drilling fluid. This also happens while drilling in oil and gas reservoirs. These polluted drilling cuttings can cause significant environmental and public health issues and cannot be discharged into the environment without treatment. The studies show that the returned drilling fluids contain heavy metals like nickel, mercury, cadmium, chromium, copper, and lead. These elements are associated with chronic diseases, including cancer (Antia et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSustainable reservoir and production engineering practices increasingly require that drilling waste management be integrated into overall field development planning, rather than treated as an isolated downstream activity (Majid \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe transport and settling behaviour of drill cuttings in drilling fluids strongly affects surface solids control efficiency and the volume of cuttings requiring treatment, as highlighted by recent work on settling velocity and hydrodynamics of cuttings in complex mud systems (Agwu et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe drilling fluid system is one of the main parts of the drilling operation and is the heart of the drilling operation. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (Tabatabaei et al. 2022) shows a schematic of the drilling fluid circulation system. Drilling fluid can undertake more than 15 critical functions depending on different situations, from providing the necessary pressure to control formation pressures and overburdens, cooling and lubricating the drill bit and drill string, carrying cuttings to the surface, achieving geological information, etc. Diesel or chemical additives are usually used to impart lubricating properties to the mud. These additives are often derived from oil. The amount of this diesel used is proportional to the need, ranging from 1 to 3 percent of the volume of the drilling mud. On the other hand, adding other chemical additives and polymers makes the drilling cuttings sufficiently contaminated that they cannot be disposed of on land or sea without treatment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eVarious methods have been proposed and implemented for treating drill cuttings, each with its advantages and disadvantages. Treatment methods include land spreading, land farming, bioremediation, reinjection, fixation with agents like cement, thermal, etc. Ilinykh et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) developed a life cycle assessment (LCA) of drilling waste management methods in Russia. They compared land spraying, disposal, solidification, and reinjection. The results illustrate that solidification has the highest impact due to cement and lime consumption, while reinjection has the lowest environmental impact.\u003c/p\u003e \u003cp\u003eIn sensitive environments, especially marine environments, the methods above have not been able to reduce the contamination levels of drilling cuttings below global standards. As a result, specialists have always been looking for new methods to treat contaminated drill cuttings.\u003c/p\u003e \u003cp\u003eOne of these methods is pyrolysis, which involves the absorption or separation of contaminants from the surface of the drill cuttings by heating them. This method has gained attention in recent years. In the pyrolysis method, researchers have compared the use of conventional heat sources, such as electrical or microwave energy, multiple times. In all these studies, the superiority of microwave techniques over other thermal methods has been proven (Beneroso et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Lu et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Hossain et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Shang et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Robinson et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2008\u003c/span\u003eb; Shang et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The main reason for this result is the selective and volumetric heating provided by microwave methods.\u003c/p\u003e \u003cp\u003eIn all previous and current methods of treating drill cuttings, the treatment capacity has always been a challenge, particularly when drilling the upper sections of the well (top holes), where a large volume of drill cuttings, along with the returning drilling fluid, is discharged onto the shale shaker screens. Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, adapted from standard drilling engineering practice, shows how much cutting is produced during drilling as a function of borehole geometry, porosity, washout, and penetration rate (Bourgoyne et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1986\u003c/span\u003e).\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:Vc=\\frac{\\left(1-{\\varnothing}\\right)\\text{*}{(D+W)}^{2}*ROP}{1029.4}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere,\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eVc is the volume of cutting in bbl/hr.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e\u0026Oslash; is formation porosity (%).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eD is the wellbore diameter in inches.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eW is wellbore washout in inches\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eROP is the rate of penetration in feet per hour.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eIn other words, the production rate of drill cuttings in the upper sections of the well is much higher than their treatment rate. In onshore drilling, due to the availability of sufficient space, these drill cuttings are usually stored in constructed pits like coral, waste pits and tanks, where they are treated over time and eventually disposed of in landfills. Due to the lack of space in offshore drilling platforms, using a sufficient number of skips to store the drill cuttings is impossible. Therefore, there is a need to address this deficiency in the treatment methods and design the methods and related equipment to allow the produced cuttings to be treated quickly onsite and discharged into the sea.\u003c/p\u003e \u003cp\u003eAlternative solutions for handling offshore cuttings usually come with secondary pollution and require significant time and cost. For example, transporting the drill cuttings to shore (skip and ship) for treatment and disposal involves challenges such as high transportation costs, the long distance between the drilling platform and the shore, and air and noise pollution caused by ship traffic. Additionally, disposing of drill cuttings onshore often leads to soil and groundwater contamination.\u003c/p\u003e\n\u003ch3\u003eAdvanced Thermal Processor (ATP)\u003c/h3\u003e\n\u003cp\u003eATP uses microwave and Infrared energy to remove oil contamination from drill cuttings. This processor is a fully integrated solution for treating drill cuttings without adversely affecting the land or marine environment.\u003c/p\u003e \u003cp\u003eThe technology is based on the advanced simultaneous use of multiple electromagnetic frequencies and a unique phase separation drum. This maximises heat and mass transfer within the system, reducing plant size, material holdup, and operating costs. In addition, the low-intensity thermal regimes allow oil to be recovered without degradation. Infrared radiation provides surface heating, which can be effective in applications where rapid surface drying or decontamination is required.\u003c/p\u003e \u003cp\u003eSome of the benefits of the ATP are:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eProcessor treats a wide range of feedstocks, including OBM, SBM and WBM, with crude and low and high water/oil contents\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eUsing a rotating drum to minimise the cutting residence time\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTreat cuttings continuously\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEnergy efficient in comparison to other methods\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTreats drill cuttings to less than 1% oil on cuttings\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNo quenching is required after processing.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCreates clean oil and water streams\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eLow-intensity thermal regimes, no oil degradation\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe processor system uses microwave and infrared energy to remove the oil contamination in drill cuttings arising from water or oil-based mud operations. The microwave energy specifically targets the moisture in the drill cuttings and the subsequent rapid evaporation, which removes the contaminating oil by the mechanism of steam stripping. Because of the manner of the energy transfer, the system operates at lower energy and temperature than conventional thermal processes.\u003c/p\u003e \u003cp\u003eThe throughput of the system depends on the available energy of the system and the moisture content of the received feed. Evaporation of moisture consumes a significant portion of the microwave and infrared energy. Therefore, preconditioning the feed by removing excess water mechanically increases the system's effective throughput. The solids processor consists of the following main components:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eEnclosed conveying system for controlled feed\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eIndustrial standard microwave generators\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eInfrared heated reactor chamber\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEnclosed solids discharge system\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eInert purge safety system\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCondenser system to separate oil and water\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eFully integrated PLC control system\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e "},{"header":"Materials and Methods","content":"\u003ch3\u003eProcess Overview\u003c/h3\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eSolids Treatment\u003c/h2\u003e \u003cp\u003eThe waste stream is fed into the processor's primary feed hopper. The waste is continuously fed from the hopper at the required rate, via an enclosed screw conveyor, to the processor.\u003c/p\u003e \u003cp\u003eThe rotating processor efficiently exposes the waste to powerful microwave and infrared energy as it passes through it. Process conditions, such as residence time and energy input, are optimally selected to ensure complete treatment of the specific waste stream. All vapours and gases released during processing are swiftly extracted from the reaction chamber by a high-efficiency fan and directed to a dedicated condensate and gas clean-up system. The fan’s suction is precisely regulated to maintain optimal operating conditions, even when feedstock composition varies.\u003c/p\u003e \u003cp\u003eTreated solids are discharged from the processor through isolation valves and conveyed via an enclosed screw conveyor to the discharge line. As the solids exit at relatively low temperatures, high-volume water quenching is not required.\u003c/p\u003e \u003cp\u003eAn inert atmosphere is maintained inside the processor, achieved initially by purging with nitrogen gas and steam generated in situ during operation. The processor is sealed to prevent any air ingress during operation. Instrumentation monitors the system for flammability, and in the event of an alarm condition, the processor is automatically purged with nitrogen gas and the system is shut down.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eOil and Water Handling\u003c/h2\u003e \u003cp\u003eThe oil/water vapour handling system (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) separates entrained solid particles from the vaporised oil and water stream through a series of separation processes. The system produces water with an oil content of 0–15 ppm and recovers oil suitable for reuse in new drilling fluid formulations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn this system, energy is applied directly to the water and oil components within the feed material, enabling rapid and efficient removal with minimal heat transfer to the inert solids in the drill cuttings. As a result, all of the applied energy is effectively used to extract the contaminants.\u003c/p\u003e \u003cp\u003eThe processor features a mechanically simple design with few moving parts. It operates gently, using slow rotation to achieve material movement and mixing, resulting in minimal wear, low maintenance requirements, and reduced repair needs.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFeed system and design criteria\u003c/h3\u003e\n\u003cp\u003eThe contaminated cuttings are received from the storage tank. A decanting centrifuge is used to remove the free water, lowering the moisture content in order to maximize the throughput of the system.\u003c/p\u003e \u003cp\u003eAny sludge generated during the natural process is reintegrated into the feed stream by metering it, along with dewasstered drill cuttings, into a continuous paddle blender. This ensures a uniform and consistent mixture.\u003c/p\u003e \u003cp\u003eThe feed is mechanically conveyed into the hopper of the ATP unit. The level in the hopper is maintained to provide an airlock. At the interior base of the hopper, a hydraulically operated sliding frame reciprocates continuously, thereby providing a continuous feed to the offtake screw. The sliding frame design is key to the material handling of the highly variable flow characteristics of the drill cuttings. The action of the sliding frame keeps the exposed flights of the offtake screw conveyor full, thereby providing accurate volumetric proportioning. The variable pitch screw drives material into the processor. As the flight length increases, the feed breaks up before entry into the ATP processor.\u003c/p\u003e \u003cp\u003eOur challenge has been to design a feed unit that can ultimately accept either pump or conveyor technology, depending on the moisture content. The feed system must be flexible enough to operate in a number of density ranges whilst generating a seal to minimise oxygen leakage into the processor. The unit needs to operate safely in extreme temperature conditions situated in an ATEX zone two area.\u003c/p\u003e \u003cp\u003eOne of the design concerns was the feed characteristics. The contaminated cutting can vary both in moisture/oil content and flow characteristics, and therefore, a unit has been selected that can handle a wide range of materials. The sliding frame of the hopper is key to the design of the unit in that it constantly agitates and mobilises the material and allows a constant volumetric flow into the processor.\u003c/p\u003e\n\u003ch3\u003eATP Drum\u003c/h3\u003e\n\u003cp\u003eThe processor consists of a rotating drum, which is inclined slightly from horizontal. The cuttings travel at a speed which is a function of the circumferential velocity. The cuttings are subjected to both microwave energy and infrared-sourced thermal energy for 15 minutes. During this time, the water and oil are driven off the cuttings into the vapour phase.\u003c/p\u003e \u003cp\u003eThe ATP drum is housed within a sealed canopy in which the infrared heaters are located. The heaters are situated along the complete length and circumference of the drum in order to distribute the energy evenly. The canopy is filled with nitrogen controlled at a slightly higher pressure to both the atmosphere and the processing chamber. This ensures that any leakage across the drum seal will be nitrogen leaking inwards, again avoiding any chance of air ingress.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eDischarge system\u003c/h2\u003e \u003cp\u003eFollowing processing, the drill cuttings are stripped of moisture and oil, resulting in a dry, powdery solid (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) that is easily conveyed. The treated material exits the processor via an inclined screw conveyor and passes through a rotary valve, which serves as an airlock at the discharge end of the system. The solids can then be safely discharged overboard. To prevent airborne dust emissions, a water mist system is employed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eVapour handling\u003c/h2\u003e \u003cp\u003eThe ATP process incorporates a recirculating gas stream that acts as a carrier gas in the process. As the stream and oil vapour are produced from the bed, the carrier gas transports the condensable to the oil/water collection system.\u003c/p\u003e \u003cp\u003eVapour exits the ATP processor at the discharge end and first passes through a gas scrubber to remove any entrained solid particles. It then enters the condensate unit, where heat is removed from the stream, causing the oil and water to condense out of the vapour phase. The resulting condensate is directed to an oil/water plate separator for oil recovery. The remaining gas flows to a loop fan that drives carrier gas recirculation, after which it is reheated and returned to the ATP processor. The condensed water is utilised in the discharge mist system to control dust emissions.\u003c/p\u003e \u003cp\u003eA desktop device was initially designed and built in the first phase in our lab. In the second phase, modifications were made, and a prototype (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) device was developed. In this study, tests were conducted using the prototype device and the results were analysed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eSafety and Inert Atmosphere Control\u003c/h2\u003e \u003cp\u003eThe drum is enclosed within a sealed canopy filled with nitrogen at a slightly higher pressure than the processing chamber. This prevents air leakage into the system, ensuring safe operation in the ATEX Zone 2 environment. Additional safety measures include continuous monitoring of oxygen levels and redundant nitrogen supply to maintain an inert atmosphere.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePost-Processing and Waste Management\u003c/h2\u003e \u003cp\u003eFollowing processing, the treated drill cuttings are converted into a dry, powder-like solid, which is easily conveyed via an inclined screw conveyor. The treated material passes through an airlock valve before final disposal. A water mist system is employed to suppress dust emissions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eEnergy Efficiency Considerations\u003c/h2\u003e \u003cp\u003eDue to the high energy demand associated with moisture evaporation, pre-conditioning of the feed is essential. Mechanical dewatering using a centrifuge reduces excess water, thereby increasing the system’s effective throughput. Additionally, energy recovery mechanisms, such as heat exchangers, can be incorporated to optimize thermal efficiency.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003ch2\u003eOffshore Project - a Case Study\u003c/h2\u003e\u003cp\u003eThis study was carried out on water-based drill cuttings contaminated with sour crude oil. The samples were collected from an offshore drilling rig in the Middle East.\u003c/p\u003e\u003cp\u003eThe samples were processed using our prototype. The objective of the project was to develop a full-scale, rig-based ATP system, with the prototype results used to define the operating envelope and required processing conditions. The design of the full-scale ATP and its feed system will be presented in a separate article. The current paper focuses on the results obtained from processing the samples using the ATP prototype unit at our lab.\u003c/p\u003e\u003cp\u003eThe prototype unit uses microwave and infrared energy to remove the oil contamination in water-based drill cuttings. Six samples of water-based drill cuttings contaminated with sour crude were received from an offshore field. After laboratory characterisation of these samples, they were processed in the ATP prototype in two batches.\u003c/p\u003e\u003cp\u003eThe treated drill cuttings contained less than 1% oil on cuttings, confirming that significant oil removal had been achieved. The recovered oil exhibited high-boiling fractions, as expected from crude oil contamination.\u003c/p\u003e\u003cp\u003eThe samples were processed using microwave-induced oil stripping. During the initial phase, the feed rate and bed depth were adjusted to maximise microwave energy absorption. Across six samples, absorption efficiency was high, with negligible reflected power recorded. Test runs were carried out under standard water-based mud (WBM) conditions, targeting a solid discharge temperature of 60°C to 100°C. The discharged solids were left to air-cool, without the use of water quenching.\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\"\u003e\u003c/div\u003e\u003ctable id=\"Tab1\" border=\"1\"\u003e \u003ccaption\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOil, water, and hydrocarbon content of water-based drill cuttings before and after treatment using the ATP prototype unit.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003c/colgroup\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\"\u003e \u003cp\u003eOil Content (% W/W)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\"\u003e \u003cp\u003eWater Content (% W/W)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\"\u003e \u003cp\u003eOil Removal Efficiency\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\"\u003e \u003cp\u003eTPH (mg/kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\"\u003e \u003cp\u003eTOG (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eSample ID\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eBefore\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eAfter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eBefore\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eAfter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eBefore\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eAfter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eBefore\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003eAfter\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e17.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e97.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e15067\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e590\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e4.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e17.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e97.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e14119\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e564\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e4.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e17.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e96.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e12733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e490\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e3.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e16.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e97.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e17340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e681\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e6.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e15.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e97.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e19740\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e731\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e95.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e9500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e205\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e3.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/table\u003e\u003c/div\u003e\u003cp\u003eTotal Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) are critical parameters used to evaluate hydrocarbon contamination in drill cuttings. TPH quantifies the total concentration of petroleum-derived hydrocarbons, while TOG encompasses both petroleum hydrocarbons and other solvent-extractable organic compounds such as animal or vegetable oils. In this study, TPH and TOG were measured using standard gravimetric and infrared spectrophotometric methods following solvent extraction, in accordance with recognised environmental testing protocols.\u003c/p\u003e\u003cp\u003eReducing TPH and TOG levels is a key objective, as it directly influences environmental safety, regulatory compliance, and the viability of waste management strategies for treated cuttings. High removal efficiencies achieved through the microwave/infrared treatment process demonstrate its effectiveness in producing near-inert solid waste, thereby supporting safe discharge or potential reuse of the treated material.\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the removal efficiency for oil content, water content, TPH, and TOG across all samples. Key observations include:\u003c/p\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003eOil Content: Removal efficiency ranges from ~ 95% to ~ 97.8%, with Sample 5 showing the highest efficiency.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eWater Content: Removal efficiency is consistently high, with most samples achieving \u0026gt; 99% removal. Sample 6, however, shows slightly lower efficiency (~ 98.5%) due to its higher initial water content.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTPH: Removal efficiency ranges from ~ 96% to ~ 98%, with Sample 6 showing the lowest efficiency (~ 95%).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTOG: Removal efficiency is consistently high, with all samples achieving \u0026gt; 96% removal.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003cp\u003eThe bar chart (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e) underscores the versatility of the treatment process in handling multiple contaminants simultaneously. This is a significant advantage over traditional methods, which often require separate treatment steps for oil, water, and solids. The ability to achieve high removal efficiencies for all contaminants in a single process step enhances the economic and environmental feasibility of the technology.\u003c/p\u003e\u003ch2\u003eOil Removal Efficiency vs. Initial Water Content\u003c/h2\u003e\u003cp\u003eThe graph of oil removal efficiency vs. initial water content (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e) shows a clear trend: as the initial water content increases, the oil removal efficiency decreases. This is particularly evident in sample 6, which has the highest initial water content (24% w/w) and the lowest oil removal efficiency (~ 95%).\u003c/p\u003e\u003cp\u003eOn the other hand, samples with lower initial water content (e.g., Sample 5 with 15.3% w/w) demonstrate higher oil removal efficiency (~ 97.8%).\u003c/p\u003e\u003cp\u003eThe inverse relationship between oil removal efficiency and initial water content can be attributed to the competition for thermal energy during the microwave/infrared treatment process. Water, being a polar molecule, absorbs microwave energy more efficiently than oil. As a result, in samples with higher water content, a significant portion of the energy is consumed in heating and evaporating water, leaving less energy available for breaking down and removing oil.\u003c/p\u003e\u003cp\u003eAdditionally, the presence of water can create a barrier effect, where water molecules surround oil droplets, making it more difficult for the thermal energy to reach and volatilise the oil.\u003c/p\u003e\u003ch2\u003eOil Removal Efficiency vs. Initial Oil + Water Content\u003c/h2\u003e\u003cp\u003eThis section examines the relationship between oil removal efficiency and the total initial fluid load (combined oil and water content-Fig.\u0026nbsp;7) present in drill cuttings. The plotted data suggest a subtle inverse trend, samples with higher fluid content (\u0026gt; 23% w/w) appear to show slightly lower oil removal efficiency compared to those with less fluid content. For instance, the sample with 28.4% oil + water content achieved only 95.0% removal efficiency, while samples with ~ 21.6–22.7% fluid content reached removal efficiencies near 97.6–97.8%.\u003c/p\u003e\u003cp\u003eThis behavior can be explained by fluid dynamics during thermal desorption. According to prior studies (e.g., Noor et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), excess water can form an insulating vapor layer around oil droplets under rapid heating, hindering direct thermal contact between the droplet surface and the heat source. This phenomenon, commonly referred to as the Leidenfrost effect, can reduce desorption efficiency, especially in fine-textured materials like drill cuttings where oil droplets are embedded within a matrix.\u003c/p\u003e\u003cp\u003eThe current trend, while based on six samples, aligns with thermodynamic expectations and highlights the potential benefit of pre-drying or moisture control prior to thermal treatment. These findings support the optimization of operating parameters based on fluid content to maximise oil removal performance.\u003c/p\u003e\u003cp\u003eThe process incorporates a gas recirculation system to transport steam and oil vapours to an oil-water separation unit. The vapour stream first passes through a gas scrubber to remove entrained solid particles before entering a condenser. Here, heat is extracted, allowing oil and water to be separated and recovered. The remaining gas is then recirculated back into the processor, enhancing energy efficiency and minimising emissions.\u003c/p\u003e\u003ch2\u003eThermogravimetric Analysis (TGA) of Treated Drill Cuttings\u003c/h2\u003e\u003cp\u003eTGA is a widely accepted technique used to monitor the weight change of materials in response to increasing temperature. In the context of drill cuttings remediation, TGA provides critical insights into the removal behavior of volatile components, such as hydrocarbons and water, and helps evaluate the energy efficiency and thermal footprint of the treatment technology.\u003c/p\u003e\u003cp\u003eFor sample 1, with an initial oil content of 5.7% w/w and water content of 17.2% w/w, the TGA curve shows a dominant mass loss of 21.17% at just 106°C. This strongly indicates the removal of surface-bound water and light volatile fractions at very low temperatures. The fact that nearly the entire oil and water content of the sample is removed below 110°C demonstrates that the ATP can operate effectively under low-temperature conditions. This early-stage vaporisation confirms the low energy demand and high thermal efficiency of the ATP process, especially when compared to traditional high-temperature methods like incineration or friction-based desorption.\u003c/p\u003e\u003cp\u003eBeyond this initial phase, the TGA (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e) trace indicates only minimal additional mass loss: 3.35% at 275°C, 2.24% at 413°C, and 31.96% at 720°C, suggesting that the remaining matrix consists mostly of inorganic or thermally stable residuals. Importantly, the near-absence of volatiles below 400°C after ATP processing confirms that contaminants such as oil and water have been nearly completely eliminated, aligning with regulatory standards such as OSPAR’s \u0026lt; 1% oil-on-cuttings threshold.\u003c/p\u003e\u003cp\u003eThis thermal profile is not only a validation of treatment completeness but also a demonstration of safe, low-discharge temperatures and environmentally compliant residue behavior. In ATP, microwave and infrared heating penetrate the matrix volumetrically, rapidly driving off moisture and releasing embedded oil droplets without overheating or structural degradation.\u003c/p\u003e\u003cp\u003eOverall, TGA confirms that ATP achieves thorough decontamination through precisely controlled, low-temperature desorption, with minimal energy input and a residue that is both stable and environmentally acceptable.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe ATP offers a significant advancement in the sustainable treatment of oil-contaminated drill cuttings. Through the integration of microwave and infrared heating within a sealed, nitrogen-controlled chamber, ATP achieves effective decontamination at lower temperatures than conventional thermal technologies. This minimises energy demand and discharge temperature, supporting cleaner offshore operations.\u003c/p\u003e\u003cp\u003eThe experimental findings confirm that ATP consistently removes oil, water, TPH, and TOGs with high efficiency, even when initial contaminant levels vary. Across all tested samples, the system consistently delivered oil removal efficiencies greater than 95%, with some reaching up to 97.8%. TGA further validated the treatment mechanism, showing that over 21% of sample weight, corresponding to oil and water, was vaporised at just 106°C. These results confirm ATP’s ability to remove the majority of volatiles under mild thermal conditions, reducing operational risk and energy consumption.\u003c/p\u003e\u003cp\u003eThe observed relationships between initial oil/water content and removal efficiency provide valuable insight into process optimisation, while the system’s ability to perform consistently across variable contamination levels confirms its industrial potential. Unique design features, such as continuous feed, a rotating drum, and low-emission processing, make ATP a technically robust alternative to skip-and-ship and other energy-intensive treatment options.\u003c/p\u003e\u003cp\u003eThis work supports broader industry efforts toward environmentally responsible waste management. Future development may focus on upscaling, energy integration, and extended economic evaluation to maximise the technology’s potential in offshore and remote settings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing financial or non-financial interests that are directly or indirectly related to the work submitted for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRoohollah Babaei-Mahani1: Conceptualization, Writing \u0026ndash; original draft, Supervision. Ali Fereidounpour: Writing - Review \u0026amp; Editing,\u0026nbsp;Visualization . Yinghe He: Writing - Review \u0026amp; Editing. Peter Scholes: Methodology, Writing - Review \u0026amp; Editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAgwu OE, Akpabio JU, Alabi SB (2018) Settling velocity of drill cuttings in drilling fluids: A review of experimental, numerical simulations and artificial intelligence studies. 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Bioresour Technol 102(22):10252\u0026ndash;10259. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.biortech.2011.08.074\u003c/span\u003e\u003cspan address=\"10.1016/j.biortech.2011.08.074\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"drill cuttings treatment, microwave/infrared processing, environmental risk mitigation, waste management, drill cuttings processor, offshore ecosystem protection","lastPublishedDoi":"10.21203/rs.3.rs-8732040/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8732040/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDrilling operations generate large volumes of drill cuttings contaminated with hydrocarbons, salts, and trace metals, creating significant environmental and regulatory challenges for offshore disposal. Most regulatory frameworks prohibit the discharge of drill cuttings containing more than 1 wt.% oil‑on‑cuttings, necessitating effective on‑site treatment technologies.\u003c/p\u003e \u003cp\u003eThis study evaluates the performance of a continuous hybrid microwave\u0026ndash;infrared thermal desorption process for the remediation of oil‑contaminated drill cuttings. Offshore water‑based drill cuttings contaminated with sour crude oil were collected from Middle Eastern drilling operations and treated using a pilot‑scale unit under inert, low‑oxygen conditions.\u003c/p\u003e \u003cp\u003eThe process achieved oil-removal efficiencies of 95.0\u0026ndash;97.8%, consistently reducing oil on cuttings to below 1 wt.%. Total Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) were reduced by more than 96% across all samples. Thermogravimetric analysis confirmed that most volatile contaminants were removed at temperatures below 110\u0026deg;C, indicating a lower thermal demand than conventional thermal treatments.\u003c/p\u003e \u003cp\u003eThe results demonstrate that hybrid microwave/infrared thermal processing is an effective and energy‑efficient approach for the treatment of offshore drill cuttings, enabling regulatory compliance while minimising secondary emissions and operational disruption.\u003c/p\u003e","manuscriptTitle":"Hybrid microwave-infrared thermal desorption for remediation of oil-contaminated offshore drill cuttings","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-26 16:55:06","doi":"10.21203/rs.3.rs-8732040/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2026-03-23T17:14:16+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2026-02-24T20:11:18+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-24T20:01:03+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2026-02-12T13:37:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-05T04:57:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2026-02-03T08:02:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"eed80bbc-a775-4c43-b356-71cc5a46cfbe","owner":[],"postedDate":"February 26th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-06T14:28:58+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-26 16:55:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8732040","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8732040","identity":"rs-8732040","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}