Curie Point Depth as a Key Indicator of Hydrocarbon Maturity in the Southeastern Niger Delta Basin: Insights From Aeromagnetic Data

Curie Point Depth as a Key Indicator of Hydrocarbon Maturity in the Southeastern Niger Delta Basin: Insights From Aeromagnetic Data | 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 Curie Point Depth as a Key Indicator of Hydrocarbon Maturity in the Southeastern Niger Delta Basin: Insights From Aeromagnetic Data Aniekan Emmanuel Ekpo, Nsikak E. Bassey, Nyakno J George, Itoro G. Udo This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5194917/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 6 You are reading this latest preprint version Abstract This study focuses on the Curie point depth (CPD) as a critical factor in determining the hydrocarbon potential of the southeastern Niger Delta Basin, using aeromagnetic data to analyze subsurface thermal structures. The Curie point depth, which marks the depth at which ferromagnetic minerals lose their magnetic properties at a temperature of approximately 580°C, varies across the basin from 23.27 km to 83.15 km, with an average of 60.36 km. These variations in CPD, combined with geothermal gradient values ranging from 6.98°C/km to 24.93°C/km, and heat flow measurements between 17.44 mW/m² and 62.33 mW/m², provide insights into the thermal maturity of hydrocarbons in different regions. The findings indicate that blocks with intermediate CPD values, such as Blocks 2, 4, 7, and 29, with depths between 55.44 km and 62.60 km, are conducive to oil exploration due to their balanced thermal regimes. Conversely, blocks with shallow CPD values, like Block 9 (23.27 km), exhibit higher heat flow and geothermal gradients, making them better suited for gas exploration due to over-maturation of hydrocarbons. In contrast, deeper CPD regions, like Block 36 (83.15 km), reflect under-mature conditions, where hydrocarbon formation has not yet reached optimal levels. This study underscores the importance of CPD in guiding hydrocarbon exploration strategies in the Niger Delta Basin. Curie temperature Hydrocarbon Maturation Niger Delta Basin Oil and Gas Exploration Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 INTRODUCTION The Curie point depth (CPD), geothermal gradient, and heat flow derived from the aeromagnetic data over the south eastern Niger Delta Basin provide profound insights into the thermal structure and hydrocarbon potential. The Niger Delta is renowned for its significant hydrocarbon reserves, largely due to its complex tectonic and sedimentary history. By examining the variations in Curie depth and geothermal parameters across the study area, we can draw critical conclusions about which parts of the basin are suitable for oil and gas exploration, and which may be under- or over-matured for hydrocarbon generation. The Niger Delta Basin originated from an unsuccessful rift junction that occurred during the tectonic divergence of the South American and African plates, coinciding with the initial opening of the South Atlantic Ocean (Doust & Omatsola, 1990 ). The rifting process in this basin commenced in the late Jurassic period and concluded in the mid-Cretaceous period. Throughout this extensive rifting phase, numerous faults emerged, with a significant number being thrust faults. Concurrently, syn-rift sedimentation took place, resulting in the deposition of sands followed by shales during the late Cretaceous. These sediments were deposited in a complex interplay of subsidence and faulting, which contributed to the distinctive stratigraphy of the Niger Delta Basin. The intricate tectonic activities and sedimentary processes during this period laid the foundational geological framework that has significantly influenced the hydrocarbon potential of the basin. In the Niger Delta Basin, there is no significant evidence of magmatic or volcanic episodes leading to widespread geothermal anomalies within its sedimentary basins. The basin's formation and evolution are predominantly characterized by rifting, sedimentary processes and magmatic intrusions activities (Whiteman, 1982 ; Doust & Omatsola, 1990 ; Tuttle et al., 1999 ). This rifting created accommodation space for thick sequences of sediment to be deposited, leading to the development of the deltaic structure (Evamy et al., 1978 ). The focus of geological activity in the Niger Delta Basin has been on faulting, subsidence, and sedimentation processes, rather than magmatism (Corredor et al., 2005 ). Geothermal anomalies in sedimentary basins are typically associated with magmatic intrusions, volcanic activity, or high heat flow from the Earth's mantle. However, the geothermal gradient in the Niger Delta Basin is more likely influenced by the thick accumulation of sediments, the burial depth of organic-rich layers, and the resulting thermal maturity of hydrocarbons, rather than by magmatic or volcanic episodes (Whiteman, 1982 ; Tuttle et al., 1999 ). While geothermal anomalies may exist in this Basin due to the thermal maturation of organic materials and sedimentary processes, they are not primarily linked to magmatic or volcanic activities but to magmatic intrusion (Evamy et al., 1978 ; Doust & Omatsola, 1990 ). This paper aims to investigate the Curie point depth as well as the thermal maturity of the south eastern part of the Niger Delta basin which have been under exploited for hydrocarbon as compared to other part of the basin. 1.1 Curie Point Depth and Thermal Maturity The Curie point is the depth at which ferromagnetic minerals, such as magnetite, lose their magnetic properties due to high temperatures, typically around 580°C for magnetite. In sedimentary basins like the Niger Delta, the thermal regime is a critical factor influencing the transformation of organic material into hydrocarbons. The depth at which the Curie point occurs can offer indirect information about the geothermal gradient and heat flow in the basin, both of which are crucial for determining the thermal maturity of hydrocarbons. In the context of the Niger Delta, the basin's thermal regime governs the maturation of kerogen into hydrocarbons. Hydrocarbon maturation occurs in specific temperature windows: oil generation typically occurs between 60°C and 120°C, while gas generation occurs at higher temperatures, generally above 120°C to around 200°C. Therefore, understanding the temperature distribution in the subsurface is key to identifying areas with potential hydrocarbon reservoirs. 1.2 GEOLOGY OF THE AREA OF STUDY The area of investigation is located in the southeastern onshore part of the Tertiary Niger Delta Basin of Nigeria. It is part of Bayelsa, Imo, Rivers, Abia, Akwa Ibom and Cross River States of southern Nigeria. The area (Fig. 1) lies between latitudes 4˚ 50' and 5˚ 50'N and longitudes 7˚ 00' and 9˚ 00'E. The study area covers approximately 24,650 km². The topographic map of the area is as shown in Fig. 2 and the geologic map of the study area is as shown in Fig. 3 . The Niger Delta Basin is an extensional rift basin located in the Gulf of Guinea on the passive continental margin near the western coast of Nigeria with suspected or proven access to Cameroon, Equatorial Guinea and São Tomé and Príncipe (Tuttle et al, 2015 ). It is one of the world’s largest Tertiary Deltas and an extremely prolific hydrocarbon province (Doust, 1990 ). It has a subaerial area of about 75,000 km², ha total area of 300,000 km², and a sediment volume of 500,000 km³ (Okiwelu et al., 2013 ; Tuttle et al, 2015 ). The sediment fill has a depth between 9 and 12 km (Merki, 1972 ; Evamy et al., 1978 ; Fatoke, 2010 ; Okiwelu et al., 2013 ). The basin is composed of different geologic formations and this indicates how this basin was formed, as well as the regional and large scale tectonics of the area. The basin being an extensional basin is flanked by other basins in the area, which formed from similar processes. According to Lehner and De Ruiter ( 1977 ), the basin lies in the extreme southwestern part of a larger tectonic structure, the Benue Trough. The eastern part of the basin is bounded by the Cameroon Volcanic Line and the transform passive continental margin (Fatoke, 2010 ). Materials The aeromagnetic data acquired by Nigerian Geological Survey Agency (NGSA) was used for the study. The materials used for this study include eight (8) magnetic sheets of 321, 322, 323, 324, 329, 330, 331 and 332. Oasis Montaj version 8.4, ArcGIS (version 10.1), Microsoft Excel and Surfer software (version 13) were employed in analyzing the data. 2.1 Data Acquisition The airborne data was acquired and assembled by Fugro Airborne Surveys, Canada between 2005 and 2010. These data were collected using Flux-gate proton precession magnetometers and the Flux- Adjusting surface data assimilation system with flight-line space of 0.1 km, tie line space of 0.5 km and terrain clearance ranging from 0.08–0.1 km along 826,000 lines. The observed potential field data were of very high resolution when likened to the 1970 aero-geophysical data. These recent potential field data were noticed to be suited for mineral and petroleum investigations as well as geological mapping (Ekpo et al., 2024 b). The International Geomagnetic Reference Field (IGRF) correction was applied to the magnetic data set to remove the regional component of the Earth's magnetic field, while isolating the local magnetic anomalies that are of interest in geophysical exploration. The IGRF is a mathematical model that represents the Earth's main magnetic field, which is largely generated by processes in the Earth's core. This model is updated every five years and provides the expected magnetic field at any location on the Earth's surface. The IGRF correction involves calculating the magnetic field using the IGRF model at the survey locations and subtracting this regional field from the observed data. This leaves the residual magnetic anomalies, which are more directly related to local geological features. The data used for this study were processed to the form of Total magnetic gridded data displayed as imageries in colour raster format (Fig. 4 ). Reduction to Equator ( RTE) being a processing technique used to simplify the interpretation of magnetic data by centering magnetic anomalies directly over their causative bodies was applied to the data. Magnetic anomalies can appear skewed or offset due to the inclination and declination of the Earth's magnetic field, particularly at lower latitudes. The RTP mathematically transforms the observed magnetic data to simulate what it would look like if the Earth's magnetic field were vertical (as it is at the magnetic poles or equator). The process involved adjusting both the amplitude and the phase of the magnetic field components. The resulting RTP data have anomalies that are centered over their sources, making it easier to correlate magnetic anomalies with subsurface structures. Residual-Regional separation was further carried out on the RTP map and the resultant residual map was used for this analysis. The map was divided into 40 overlapping spectral blocks (Fig. 4 b) and spectral analysis was carried for each of the blocks. 2.2 Methodology To estimate the Curie point (basal) depth \(\:{Z}_{b}\) of the magnetic source, Tanaka et al. ( 1999 ) assumed the magnetic source layer extends infinitely in all horizontal directions. They considered the depth to be proportional to the horizontal scale of the magnetic source, with the magnetization M(x,y) being a random function of x and y. Blakely ( 1995 ) demonstrated that the power density spectra of the total field anomaly P is given by: $$\:P\left({k}_{x},{k}_{y}\right)=P({k}_{x},{k}_{y})\times\:F({k}_{x},{k}_{y})$$ 1 $$\:F\left({k}_{x},{k}_{y}\right)=4{\pi\:}^{2}{C}_{m}^{2}{\left|{\theta\:}_{m}\right|}^{2}{\left|{\theta\:}_{f}\right|}^{2}{e}^{-2\left|k\right|{Z}_{t}}{\left[1-{e}^{-\left|k\right|({Z}_{b}-{Z}_{t})}\right]}^{2}$$ 2 Where 𝑃 is the power density spectrum of the Magnetization, 𝐶 𝑚 is proportionality constant, 𝜃 𝑚 and 𝜃 𝑓 are factors for magnetization and geomagnetic field direction respectively, 𝑍 𝑏 𝑎𝑛𝑑 𝑍 𝑡 being the depths to the bottom and top of the magnetic source respectively. The equation can be simplified by noting that all terms except |𝜃 𝑚 | 2 𝑎𝑛𝑑 |𝜃 𝑓 | 2 are radially symmetric. Furthermore, the radial averages of 𝜃 𝑚 𝑎𝑛𝑑 𝜃 𝑓 are constants. If (𝑥,) is completely random and uncorrelated, (𝑘𝑥,) is a constant. Hence, the radial average of P is: $$\:P\left(\left|k\right|\right)=A{e}^{-2\left|k\right|{Z}_{t}}{\left[1-{e}^{-\left|k\right|({Z}_{b}-{Z}_{t})}\right]}^{2}$$ 3 Where A is a constant and k is the wave number. For wavelengths less than about twice the thickness of the layer Eq. ( 3 ) can be written as Eq. ( 4 ) $$\:\text{ln}P{\left|k\right|}^{1/2}=\text{ln}B-\left|k\right|{Z}_{t}$$ 4 Where B is a constant. The upper bound of magnetic source 𝑍 𝑡 could be estimated by fitting a straight line through the high-wave number part of a radially average power spectrum \(\:[\text{ln}P{\left|k\right|}^{1/2}]\) $$\:\text{ln}P{\left|k\right|}^{1/2}=C{e}^{-\left|k\right|{Z}_{0}}({e}^{-\left|k\right|{Z}_{t}-{Z}_{0}}-{e}^{-\left|k\right|{Z}_{b}-{Z}_{0}})$$ 5 Where C is a constant, a long wavelength, Eq. ( 5 ) can be rewritten as; $$\:\text{ln}P{\left|k\right|}^{1/2}=C{e}^{-\left|k\right|{Z}_{0}}({e}^{-\left|k\right|(-s)}-{e}^{-\left|k\right|\left(s\right)})\approx\:C{e}^{-\left|k\right|{Z}_{0}}2\left|k\right|s$$ 6 Where 2 S is the thickness of the magnetic source. From Eq. ( 6 ), it can be concluded that; $$\:\text{ln}(\frac{P{\left|k\right|}^{1/2}}{\left|k\right|})=\text{ln}D-\left|k\right|{Z}_{0}$$ 7 Where D is a constant. The centroid of the magnetic source 𝑍 𝑜 can be estimated by fitting a straight line through the lower-wave number part of the radially average frequency scale power spectrum average power Then the Basal Depth 𝑍 𝑏 of the magnetic source will be calculated from the equation, $$\:{Z}_{b}=2{Z}_{0}-{Z}_{t}$$ 8 𝑍 𝑂 is the centriod of the magnetic source is the depth to the top of the magnetic source, while 𝑍 𝑏 is the basal depth of the magnetic sources assumed to be the Curie point depth (Bhattacharyya and Lue, 1975; Okubo et al., 1985 ). At the basal depth 𝑍 𝑏 ferromagnetic minerals transition into paramagnetic minerals due to reaching a critical temperature of approximately 580°C at that depth. This temperature marks the Curie point, where the magnetic properties of minerals fundamentally change. Hence, the fundamental principle governing conductive heat transport in this context is Fourier's law of heat conduction and it states that the heat flow through a material is proportional to the negative gradient of temperature and can be expressed mathematically as: $$\:q=-k\frac{dT}{dZ}$$ 9 Where q is the heat flux measured in units of energy with SI unit of W/m 2 , k being the coefficient of thermal conductivity which is a measure of how easily heat flows through a material, with SI unit of 𝑊𝑚 −1 𝐾 −1 𝑜𝑟 𝑊𝑚 −1 ℃ −1 and \(\:dT/dZ\) is the temperature gradient. . Tanaka et al. ( 1999 ) demonstrated that the depth of a thermal isotherm, such as the Curie point, is inversely proportional to the heat flow. This relationship implies that higher heat flow results in a shallower isotherm depth, while lower heat flow leads to a deeper isotherm. Under the assumptions of a one-dimensional heat conduction model, where the temperature variation occurs solely in the vertical direction and the temperature gradient \(\:dT/dZ\) remains constant, Fourier's law simplifies to: $$\:{Z}_{b}=\frac{T}{q}$$ 10 Where \(\:{Z}_{b}\) is the basal depth, T is the temperature at depth \(\:{Z}_{b}\) (typically the Curie temperature, around 580°C) and q the heat flow. In this simplified model, the constancy of the temperature gradient implies that the temperature changes linearly with depth. Thus, by understanding the thermal conductivity and the heat flow in the region, one can estimate the depth at which significant thermal transformations, such as the Curie point transition, occur. Hence the thermal gradient is given as; $$\:\frac{dT}{dZ}=\frac{{T}_{c}-{T}_{s}}{{Z}_{b}}=\frac{580℃-{T}_{s}}{{Z}_{b}}$$ 11 Where 𝑇 𝑠 is the temperature at the surface. The Heat Flow values were calculated using Eq. ( 12 ) $$\:q=k\left(\frac{dT}{dZ}\right)=k\left(\frac{580℃-{T}_{s}}{{Z}_{b}}\right)$$ 12 Where q is the heat flow and k the coefficient of thermal conductivity. The k value might differs within the study area due to variation in the different rock units that are within the study area. The mean value for the coefficient of thermal conductivity in the study area varies depending on the specific geological formations and types of rocks present. However, for sedimentary basins like the Niger Delta, typical values for thermal conductivity generally range between 1.5 to 3.5 Wm − 10 C −1 . For instance, in sedimentary rocks commonly found in the Niger Delta such as sandstones and shales, the thermal conductivity is often around 2.5–3.5 Wm − 10 C −1 for sandstones and 1.5–2.5 Wm − 10 C −1 for shales (Obande & Ojo, 2008 ; Onwuemesi & Oha, 2008 ). The thermal conductivity of 2.5 Wm − 10 C −1 was used in this work. Results The first result obtained are those of the spectral plot shown in Fig. 5, just a sample because all the results for depth to top (Z t ) and depth to centroid (Z o ) obtained from the plots, Curie Point Depth (Z b ), geothermal gradient (GTG) and Heat flow (HF) obtain from the use of equations 8 , 9 and 10 respectively also presented on Table 1 . The results presented on Table 1 was harnessed and used to processed the maps of depth to bottom (Fig. 6 ), geothermal gradient (Fig. 7 ) and heat flow shown in Fig. 8 . . Figure 5 Total magnetic intensity (TMI) map Table 1 Calculated Average Curie point depth, Geothermal gradient and Heat flow from Spectral analysis from total magnetic intensity (TMI) map Block LONGITUDE LATITUDE Depth to Centriod Z o (Km) Depth to top Z t (Km) Curie point depth Z b (Km) Geothermal gradient \(\:\frac{\varvec{d}\varvec{T}}{\varvec{d}\varvec{z}}\) ( o C/Km) Heat flow Q (mWm − 2 ) 1 7.2 5.4 34.92 1.63 68.20 8.50 21.26 2 7.4 5.4 28.69 1.94 55.44 10.46 26.15 3 7.6 5.4 32.42 3.46 61.38 9.45 23.62 4 7.8 5.4 30.09 2.32 57.85 10.03 25.06 5 8.0 5.4 30.21 4.20 56.21 10.32 25.79 6 8.2 5.4 28.42 3.48 53.36 10.87 27.17 7 8.4 5.4 29.68 2.31 57.05 10.17 25.41 8 8.6 5.4 17.82 2.51 33.13 17.51 43.77 9 8.8 5.4 12.89 2.51 23.27 24.93 62.33 10 7.2 5.2 37.90 1.12 74.67 7.77 19.42 11 7.4 5.2 35.14 1.41 68.87 8.42 21.05 12 7.6 5.2 22.09 1.66 42.51 13.64 34.11 13 7.8 5.2 29.88 1.73 58.04 9.99 24.98 14 8.0 5.2 26.18 2.37 50.00 11.60 29.00 15 8.2 5.2 27.12 1.64 52.60 11.03 27.56 16 8.4 5.2 34.89 2.50 67.28 8.62 21.55 17 8.6 5.2 19.80 2.35 37.26 15.57 38.92 18 8.8 5.2 18.32 2.56 34.08 17.02 42.55 19 7.2 5.0 39.82 1.48 78.15 7.42 18.55 20 7.4 5.0 25.83 1.51 50.15 11.56 28.91 21 7.6 5.0 31.87 1.50 62.23 9.32 23.30 22 7.8 5.0 30.29 3.12 57.46 10.09 25.23 23 8.0 5.0 32.08 0.92 63.23 9.17 22.93 24 8.2 5.0 32.10 1.02 63.18 9.18 22.95 25 8.4 5.0 39.64 3.64 75.64 7.67 19.17 26 8.6 5.0 28.56 3.07 54.04 10.73 26.83 27 7.2 4.8 40.24 1.47 79.01 7.34 18.35 28 7.4 4.8 34.56 1.16 67.97 8.53 21.33 29 7.6 4.8 31.93 1.26 62.60 9.26 23.16 30 7.8 4.8 37.59 2.05 73.14 7.93 19.82 31 8.0 4.8 31.59 2.46 60.73 9.55 23.88 32 8.2 4.8 39.22 1.89 76.55 7.58 18.94 33 8.4 4.8 36.83 1.75 71.92 8.06 20.16 34 7.2 4.6 26.63 1.14 52.11 11.13 27.82 35 7.4 4.6 40.08 2.29 77.86 7.45 18.62 36 7.6 4.6 42.68 2.22 83.15 6.98 17.44 37 7.8 4.6 35.57 1.57 69.57 8.34 20.84 38 8.0 4.6 34.04 1.41 66.67 8.70 21.75 39 8.2 4.6 33.66 1.30 66.02 8.78 21.96 40 8.4 4.6 27.01 2.36 51.67 11.23 28.06 AVERAGE 60.36 10.30 25.74 The Curie Point Depth (CPD) Map ( Fig. 6 ) which indicate the depth at which the magnetic anomaly loses its magnetism at Curie temperature (𝑇𝑐) has it lowest and highest values as 23.27 km (Block 9) and 83.15 km (Block 36) respectively with an average depth of 60.36 km. The Geothermal Gradient Map ( Fig. 7 ) shows the rate of depth dependent temperature growth ranging between 6.98 ℃𝑘𝑚 −1 to 24.93 ℃𝑘𝑚 −1 with an average value of 10.30 ℃𝑘𝑚 −1 . The Heat Flow values ranges between 17.44 𝑚𝑊𝑚 −2 to 62.33 𝑚𝑊𝑚 −2 1 with an average value of 25.74 𝑚𝑊𝑚 −2 . Discussion 3.1 Curie Point Depth and Its Geological Implications The Curie point depth is a key thermal marker in understanding the subsurface temperature distribution. It refers to the depth at which magnetic minerals lose their magnetism due to reaching a critical temperature, typically around 580°C. This depth can also provide indirect insights into the geothermal gradient and overall heat flow in the crust, which are essential factors in hydrocarbon maturation. In the Niger Delta Basin, the temperature profile with depth controls the maturation of organic matter into oil and gas. The oil window, generally between 60°C and 120°C, is the temperature range within which organic-rich sediments begin to generate hydrocarbons, while the gas window occurs at higher temperatures, generally above 120°C to around 200°C. The deeper the Curie point, the cooler the subsurface thermal regime, and the less likely it is for organic matter to mature into hydrocarbons at accessible depths. Conversely, shallow Curie points suggest a more thermally active crust, potentially leading to faster maturation of hydrocarbons, and, in some cases, over-maturation, where oil is converted to gas or lost due to excessive heat. 3.2 Mature Regions for Hydrocarbon Exploration Mature regions, where the thermal conditions are optimal for hydrocarbon generation without pushing the organic matter into over-maturation, are particularly important for both oil and gas exploration. In the attached data, certain blocks such as Block 2, Block 4, Block 7, and Block 29 demonstrate this balance. These blocks have Curie depths that range between 55.44 km and 62.60 km, which, when coupled with geothermal gradients of approximately 9.32°C/km to 10.17°C/km, indicate a stable subsurface environment conducive to oil and gas maturation. In these areas, the heat flow is moderate, ranging from 23.16 mW/m² to 25.41 mW/m², reflecting a consistent, moderate input of thermal energy from the Earth’s interior. This suggests that organic-rich sediments located in these regions are likely to have reached the temperatures necessary for oil and possibly early-stage gas generation, without the risk of over-maturation. Geologically, these areas might be located in the central or tectonically stable parts of the basin where sedimentation rates and heat flow have balanced out over time, creating ideal conditions for hydrocarbon preservation and maturation. In the context of the Niger Delta, these blocks represent regions where exploration is likely to yield mature hydrocarbons, particularly oil, due to the moderate subsurface heating. 3.3 Over-Matured Regions for Hydrocarbon Exploration In contrast, over-matured regions are characterized by very shallow Curie depths, high geothermal gradients, and elevated heat flow, which together indicate a much more thermally dynamic subsurface. In the attached data, Blocks 8, 9, and 18 stand out as over-matured zones. Block 9, for instance, has an extremely shallow Curie depth of 23.27 km, accompanied by a high geothermal gradient of 24.93°C/km and a heat flow of 62.33 mW/m². These thermal conditions suggest that the subsurface in this region has experienced excessive heating, driving the maturation of hydrocarbons beyond the oil window and into the gas window or, in extreme cases, leading to the thermal degradation of hydrocarbons. The high heat flow in these blocks may be attributed to localized tectonic or magmatic activity, which could introduce additional heat into the system. In the Niger Delta, such zones may be associated with faulting or other tectonic processes that bring deeper, hotter materials closer to the surface. In over-mature regions, the potential for oil exploration diminishes, as the elevated temperatures likely caused any oil to be over-cooked into gas or possibly burned off entirely. However, these areas may still hold significant gas reserves, as the high thermal gradients would have facilitated the cracking of oil into natural gas. Thus, these blocks are more suited for gas exploration, with Block 9, in particular, presenting a strong candidate for further investigation into gas reservoirs. 3.4 Under-Matured Regions for Hydrocarbon Exploration On the opposite end of the spectrum, under-matured regions are characterized by deep Curie point depths, low geothermal gradients, and correspondingly low heat flow, resulting in cooler subsurface conditions. Blocks such as Block 36, Block 19, Block 32, and Block 35 fit into this category, with Block 36 having a particularly deep Curie depth of 83.15 km, a low geothermal gradient of 6.98°C/km, and a heat flow of only 17.44 mW/m². These regions represent parts of the basin where the organic material has not yet been exposed to sufficient temperatures to generate hydrocarbons in commercial quantities. Geologically, under-matured regions in the Niger Delta are often associated with tectonically stable, cooler areas, possibly situated farther from the heat-generating influences of tectonic activity or magmatic intrusions. These areas are more likely to be found in the deeper, older sections of the basin where the thermal regime has remained relatively cool over geologic time scales. In these zones, the organic material is preserved but remains immature, meaning that it has not yet undergone the necessary thermal transformation into hydrocarbons. Exploration in such areas might yield little in the way of immediate hydrocarbon production, but they could represent future prospects if tectonic or magmatic activity were to increase the regional heat flow, thus maturing the organic material into oil or gas over time. 3.5 Implications for Hydrocarbon Exploration in the Niger Delta The variation in Curie point depth, geothermal gradient, and heat flow across the study area reflects the heterogeneity of the subsurface thermal regime in the Niger Delta Basin. Regions with moderate Curie depths and geothermal gradients, such as Blocks 2, 4, 7, and 29, are prime candidates for oil exploration, as they provide the optimal thermal conditions for hydrocarbon maturation without the risk of over-maturation. These blocks represent areas where the thermal regime has allowed organic-rich sediments to transform into oil and possibly early-stage gas, making them highly attractive targets for exploration. In contrast, blocks such as 8, 9, and 18, which exhibit shallow Curie depths, high geothermal gradients, and elevated heat flow, are more suited for gas exploration. These regions have likely experienced excessive heat, pushing hydrocarbons beyond the oil window into the gas window. The thermal conditions in these blocks are consistent with rapid maturation and gas generation, making them ideal for gas-focused exploration strategies. Finally, under-matured regions such as Blocks 36, 19, and 35 are cooler and less thermally evolved. These regions may contain large amounts of organic material that have not yet matured into hydrocarbons due to insufficient heating. While these areas may not be immediate targets for exploration, they could represent long-term prospects if heat flow increases or if alternative exploration techniques, such as enhanced geothermal energy, become viable. Conclusion The Curie point depth, geothermal gradient, and heat flow data from the attached study provide crucial insights into the hydrocarbon maturity of different parts of the study area, which can be extended to the Niger Delta Basin. Mature areas, such as those in blocks 2, 4, 7, and 29, are likely to offer the best potential for oil exploration due to their balanced thermal regime. Over-matured areas, particularly blocks 8, 9, and 18, are more suitable for gas exploration, as the intense heat flow has likely driven oil to over-mature into gas. Under-matured regions, like blocks 19, 32, and 36, are currently too cool for significant hydrocarbon generation and represent areas where further heat input may be needed to mature the organic material into hydrocarbons. 4.1 Recommendation The following recommendation have been proposed from these studies: Focus Oil Exploration in Moderately Mature Regions: Blocks with moderate Curie point depths (55–62 km) and geothermal gradients (9–10°C/km), such as Blocks 2, 4, 7, and 29, are optimal for oil exploration as they provide favorable thermal conditions for hydrocarbon maturation. Prioritize Gas Exploration in Over-Matured Zones: Blocks with shallow Curie depths and high geothermal gradients, such as Block 9, should be prioritized for gas exploration due to their thermally active subsurface, which has likely pushed hydrocarbons beyond the oil window into gas. Consider Long-Term Potential of Under-Matured Areas: Blocks with deep Curie points and low geothermal gradients, such as Block 36, are currently under-mature for hydrocarbons but may represent future opportunities if heat flow increases or alternative exploration techniques become viable. Geophysical Monitoring: Continuous geophysical monitoring of the study area is recommended to track thermal evolution and tectonic activity, which could alter the thermal maturity of hydrocarbons over time. Declarations Conflict of interest . The author declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. HUMAN ANIMAL RIGHTS: This article does not contain studies with human or animal subject. References Ajakaiye, D. E. (1985). Geothermal gradients in Nigeria and their implications for petroleum exploration. Journal of African Earth Sciences, 3(3), 511-520. Ajao, K. R., Ayodele, T. R., & Jegede, O. O. (2016). An assessment of the geothermal potential of the Niger Delta using oil and gas well temperature data. Renewable Energy, 85, 717-725. Bhattacharyya, B. K., & Leu, L. K. (1975). Analysis of magnetic anomalies over Yellowstone National Park: Mapping of Curie point isothermal surface for geothermal reconnaissance. Journal of Geophysical Research, 80(32), 4461-4465. Blakely, R. J. (1995). Potential Theory in Gravity and Magnetic Applications. Cambridge University Press. Corredor, F., Shaw, J. H., & Bilotti, F. (2005). Structural styles in the deep-water fold and thrust belts of the Niger Delta. American Association of Petroleum Geologists Bulletin, 89(6), 753-780. Doust, H. (1990). Petroleum geology of the Niger Delta. Geological Society, London, Special Publications, 50(1), 365-372. Doust, H., and Omatsola, E. (1990). Niger Delta: American Association of Petroleum Geologists Memoir 48. Ekine, A. S., & Iyabe, P. E. (2009). Heat flow studies in the Niger Delta basin. Geothermal Energy, 34(4), 523-531. Ekpo A. E., BasseyN. E., George N. J. (2024). Aero-gravity data analysis for delineating possible channels of mineralizations migration through lineament. A case study of Southeastern Niger Delta, Nigeria. AKSU Annels of Sustainable Development 2(1), 139-168, 2024. https://doi.org/10.60787/AASD-v2i1-35. Ekpo, A. E., Bassey, N. E., George, N. J., & Udo, I. G. (2024). Depth to basement estimation from aerogravity data over the Southeastern part of Niger Delta region of Nigeria. Researchers Journal of Science and Technology , 4 (5), 44–66. Retrieved from https://rejost.com.ng/index.php/home/article/view/135 Evamy, B. D., Haremboure, J., Kamerling, P., Knaap, W. A., Molloy, F. A., & Rowlands, P. H. (1978). Hydrocarbon habitat of the Tertiary Niger Delta. American Association of Petroleum Geologists Bulletin, 62(1), 1-39. Fatoke, A. O. (2010). Sequence stratigraphic framework of the paralic Agbada Formation, Northern depobelt, onshore Niger Delta, Nigeria. PhD Dissertation, University of Texas at Dallas. Lehner, P., & De Ruiter, P. A. C. (1977). Structural history of Atlantic Margin of Africa. American Association of Petroleum Geologists Bulletin, 61(7), 961-981. Merki, P. J. (1972). Structural geology of the Cenozoic Niger Delta. First Conference on African Geology, Ibadan, Nigeria, 635-646. Okiwelu, A. A., Adebayo, O. E., & Onyemesili, M. N. (2013). Sedimentology and sequence stratigraphy of the western Niger Delta. Nigerian Journal of Science, 47(1), 81-102. Okubo, Y., Graf, R. J., Hansen, R. O., Ogawa, K., & Tsu, H. (1985). Curie point depths of the Island of Kyushu and surrounding areas, Japan. Geophysics, 50(3), 481-494. Omaghomi, E., Adepelumi, A. A., & Adagunodo, T. A. (2013). Geothermal energy potential of the Niger Delta Basin from thermal gradient and heat flow data. Journal of Renewable and Sustainable Energy, 5(6), 063103. Tanaka, A., Okubo, Y., & Matsubayashi, O. (1999). Curie point depth based on spectrum analysis of the magnetic anomaly data in East and Southeast Asia. Tectonophysics, 306(3-4), 461-470. Tuttle, M. L. W., Charpentier, R. R., & Brownfield, M. E. (1999). The Niger Delta Petroleum System: Niger Delta Province, Nigeria, Cameroon, and Equatorial Guinea, Africa. U.S. Geological Survey Open-File Report 99-50-H. Tuttle, M. L., Charpentier, R. R., & Brownfield, M. E. (2015). The Niger Delta Petroleum System: Niger Delta Province, Nigeria, Cameroon, and Equatorial Guinea, Africa. US Geological Survey Bulletin, 2207-B. Whiteman, A. J. (1982). Nigeria: Its Petroleum Geology, Resources and Potential. Graham & Trotman. Nigerian Meteorological Agency (NIMET). (2023). Climate Data and Reports. Retrieved from [NIMET website](https://www.nimet.gov.ng). Obande, E. G., & Ojo, S. B. (2008). Thermal conductivity and heat flow estimates in parts of the Niger Delta, Nigeria. Journal of African Earth Sciences, 50(2-3), 164-170. Onwuemesi, A. G., & Oha, I. A. (2008). Geothermal gradients and subsurface temperature variations in parts of the Niger Delta Basin, Nigeria. Geothermics, 37(4), 476-484. Cite Share Download PDF Status: Under Revision Version 1 posted Reviewers agreed at journal 10 Nov, 2024 Reviewers invited by journal 01 Nov, 2024 Editor invited by journal 31 Oct, 2024 Editor assigned by journal 30 Oct, 2024 First submitted to journal 29 Oct, 2024 Editorial decision: Major revisions 16 Oct, 2024 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-5194917","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":372857745,"identity":"601a3957-b604-4049-999d-8ee926f18184","order_by":0,"name":"Aniekan Emmanuel Ekpo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/UlEQVRIiWNgGAWjYHACgwNQBjMQ2wAxY+MBnIqxaEkDaWkgqAXGAGk5DGbh1cLffnjjgZ85Nnm67WcfGxf8Om+3tv0w0JYam2hcWiTOpBUc7N2WVmx2Jt04eWbf7eRtZxKBWo6l5Tbg0nODx+AA77bDidsOpDEf5u25nWx2AKiFseEwTi3yQC0H/4K0nH8G0nIu2ez8Q/xaDIBaDoNtuZHGnMzz44Cd2Q0CthgC/XJYdlsaUMszZmPehuQEsxtAWxLw+EXu+OHNH99uswE6LI1ZmuePnb3Z+fSHDz7U2OD2PgpgbGNIBKtMIEo5GPxhsCde8SgYBaNgFIwUAAA0E2we/1PsCAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-2967-4346","institution":"Akwa Ibom State University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Aniekan","middleName":"Emmanuel","lastName":"Ekpo","suffix":""},{"id":372857746,"identity":"2ff25152-7bb2-47df-99c3-6cf1f5cb7d99","order_by":1,"name":"Nsikak E. Bassey","email":"","orcid":"","institution":"Akwa Ibom State University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Nsikak","middleName":"E.","lastName":"Bassey","suffix":""},{"id":372857747,"identity":"afe0da5b-7f29-4916-a6ed-e52705f8ef32","order_by":2,"name":"Nyakno J George","email":"","orcid":"","institution":"Akwa Ibom State University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Nyakno","middleName":"J","lastName":"George","suffix":""},{"id":372857748,"identity":"5830b339-1d77-40e0-b688-afe1ef437feb","order_by":3,"name":"Itoro G. Udo","email":"","orcid":"","institution":"Akwa Ibom State University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Itoro","middleName":"G.","lastName":"Udo","suffix":""}],"badges":[],"createdAt":"2024-10-02 21:09:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5194917/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5194917/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":68917770,"identity":"638ace85-099c-430e-b418-633583a03bdf","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1520654,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 1.1:\u003c/strong\u003e Location map of the study area.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/379a6ada3341f01e19527b76.png"},{"id":68917777,"identity":"231dcccd-c5e7-4b6c-b049-873db2be5f2c","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1757185,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e Topographic map of the study area. \u003cstrong\u003e(b)\u003c/strong\u003e 3D view of topographic map of the study area (USGS).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/7b85fb721fbfc7c2b617f8fa.png"},{"id":68917772,"identity":"dc9ad187-682c-4757-92ff-46b2bb494add","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":937009,"visible":true,"origin":"","legend":"\u003cp\u003eGeologic map of the study area (Ekpo et al., 2024a).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/3433d09bdee0fb4a89dfa2f4.png"},{"id":68918109,"identity":"313c23f5-4bef-4183-bd70-6b7fb8c51908","added_by":"auto","created_at":"2024-11-13 13:22:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2937391,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea:\u003c/strong\u003e Total magnetic intensity (TMI) map\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb:\u003c/strong\u003e Residual magnetic map showing 40 overlapping spectral blocks\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/4a929e50d287bfce22aeef91.png"},{"id":68917775,"identity":"476dfa23-d0af-4135-9dfd-02cccf842105","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":217276,"visible":true,"origin":"","legend":"\u003cp\u003eTotal magnetic intensity (TMI) map\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/755d74b2609c6ee3e88ff3d7.png"},{"id":68917771,"identity":"3216d4da-15c2-4f81-99df-2cf9fc1ec6b7","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":566647,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCurie point depth map\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/69090a8846fcb2f87f178685.png"},{"id":68919537,"identity":"212be89a-af22-4742-a192-b030ca044648","added_by":"auto","created_at":"2024-11-13 13:30:49","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":291883,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGeothermal gradient map\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/b104a536b5b8efb004f7ac44.png"},{"id":68917774,"identity":"bda752a7-cc9d-49c8-8428-8aaff66f28a1","added_by":"auto","created_at":"2024-11-13 13:14:49","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":311074,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHeat flow map\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/5699c4afc9a185a8e7328da3.png"},{"id":68920432,"identity":"fd2c0f12-5830-4742-bf5c-2cfb53b8a1a3","added_by":"auto","created_at":"2024-11-13 13:39:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12370518,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5194917/v1/439e7341-ec22-44e9-aaf0-b1079467f004.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eCurie Point Depth as a Key Indicator of Hydrocarbon Maturity in the Southeastern Niger Delta Basin: Insights From Aeromagnetic Data\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe Curie point depth (CPD), geothermal gradient, and heat flow derived from the aeromagnetic data over the south eastern Niger Delta Basin provide profound insights into the thermal structure and hydrocarbon potential. The Niger Delta is renowned for its significant hydrocarbon reserves, largely due to its complex tectonic and sedimentary history. By examining the variations in Curie depth and geothermal parameters across the study area, we can draw critical conclusions about which parts of the basin are suitable for oil and gas exploration, and which may be under- or over-matured for hydrocarbon generation.\u003c/p\u003e \u003cp\u003eThe Niger Delta Basin originated from an unsuccessful rift junction that occurred during the tectonic divergence of the South American and African plates, coinciding with the initial opening of the South Atlantic Ocean (Doust \u0026amp; Omatsola, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). The rifting process in this basin commenced in the late Jurassic period and concluded in the mid-Cretaceous period. Throughout this extensive rifting phase, numerous faults emerged, with a significant number being thrust faults. Concurrently, syn-rift sedimentation took place, resulting in the deposition of sands followed by shales during the late Cretaceous. These sediments were deposited in a complex interplay of subsidence and faulting, which contributed to the distinctive stratigraphy of the Niger Delta Basin. The intricate tectonic activities and sedimentary processes during this period laid the foundational geological framework that has significantly influenced the hydrocarbon potential of the basin. In the Niger Delta Basin, there is no significant evidence of magmatic or volcanic episodes leading to widespread geothermal anomalies within its sedimentary basins. The basin's formation and evolution are predominantly characterized by rifting, sedimentary processes and magmatic intrusions activities (Whiteman, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Doust \u0026amp; Omatsola, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Tuttle et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1999\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis rifting created accommodation space for thick sequences of sediment to be deposited, leading to the development of the deltaic structure (Evamy et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1978\u003c/span\u003e). The focus of geological activity in the Niger Delta Basin has been on faulting, subsidence, and sedimentation processes, rather than magmatism (Corredor et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGeothermal anomalies in sedimentary basins are typically associated with magmatic intrusions, volcanic activity, or high heat flow from the Earth's mantle. However, the geothermal gradient in the Niger Delta Basin is more likely influenced by the thick accumulation of sediments, the burial depth of organic-rich layers, and the resulting thermal maturity of hydrocarbons, rather than by magmatic or volcanic episodes (Whiteman, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Tuttle et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1999\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWhile geothermal anomalies may exist in this Basin due to the thermal maturation of organic materials and sedimentary processes, they are not primarily linked to magmatic or volcanic activities but to magmatic intrusion (Evamy et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Doust \u0026amp; Omatsola, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1990\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis paper aims to investigate the Curie point depth as well as the thermal maturity of the south eastern part of the Niger Delta basin which have been under exploited for hydrocarbon as compared to other part of the basin.\u003c/p\u003e \u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003e1.1 Curie Point Depth and Thermal Maturity\u003c/h2\u003e \u003cp\u003eThe Curie point is the depth at which ferromagnetic minerals, such as magnetite, lose their magnetic properties due to high temperatures, typically around 580\u0026deg;C for magnetite. In sedimentary basins like the Niger Delta, the thermal regime is a critical factor influencing the transformation of organic material into hydrocarbons. The depth at which the Curie point occurs can offer indirect information about the geothermal gradient and heat flow in the basin, both of which are crucial for determining the thermal maturity of hydrocarbons.\u003c/p\u003e \u003cp\u003eIn the context of the Niger Delta, the basin's thermal regime governs the maturation of kerogen into hydrocarbons. Hydrocarbon maturation occurs in specific temperature windows: oil generation typically occurs between 60\u0026deg;C and 120\u0026deg;C, while gas generation occurs at higher temperatures, generally above 120\u0026deg;C to around 200\u0026deg;C. Therefore, understanding the temperature distribution in the subsurface is key to identifying areas with potential hydrocarbon reservoirs.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e1.2 GEOLOGY OF THE AREA OF STUDY\u003c/h2\u003e \u003cp\u003eThe area of investigation is located in the southeastern onshore part of the Tertiary Niger Delta Basin of Nigeria. It is part of Bayelsa, Imo, Rivers, Abia, Akwa Ibom and Cross River States of southern Nigeria. The area (Fig.\u0026nbsp;1) lies between latitudes 4˚ 50' and 5˚ 50'N and longitudes 7˚ 00' and 9˚ 00'E. The study area covers approximately 24,650 km\u0026sup2;. The topographic map of the area is as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and the geologic map of the study area is as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Niger Delta Basin is an extensional rift basin located in the Gulf of Guinea on the passive continental margin near the western coast of Nigeria with suspected or proven access to Cameroon, Equatorial Guinea and S\u0026atilde;o Tom\u0026eacute; and Pr\u0026iacute;ncipe (Tuttle et al, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). It is one of the world\u0026rsquo;s largest Tertiary Deltas and an extremely prolific hydrocarbon province (Doust, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). It has a subaerial area of about 75,000 km\u0026sup2;, ha total area of 300,000 km\u0026sup2;, and a sediment volume of 500,000 km\u0026sup3; (Okiwelu et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Tuttle et al, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The sediment fill has a depth between 9 and 12 km (Merki, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1972\u003c/span\u003e; Evamy et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Fatoke, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Okiwelu et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The basin is composed of different geologic formations and this indicates how this basin was formed, as well as the regional and large scale tectonics of the area. The basin being an extensional basin is flanked by other basins in the area, which formed from similar processes. According to Lehner and De Ruiter (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1977\u003c/span\u003e), the basin lies in the extreme southwestern part of a larger tectonic structure, the Benue Trough. The eastern part of the basin is bounded by the Cameroon Volcanic Line and the transform passive continental margin (Fatoke, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Materials","content":"\u003cp\u003eThe aeromagnetic data acquired by Nigerian Geological Survey Agency (NGSA) was used for the study. The materials used for this study include eight (8) magnetic sheets of 321, 322, 323, 324, 329, 330, 331 and 332. Oasis Montaj version 8.4, ArcGIS (version 10.1), Microsoft Excel and Surfer software (version 13) were employed in analyzing the data.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Data Acquisition\u003c/h2\u003e \u003cp\u003eThe airborne data was acquired and assembled by Fugro Airborne Surveys, Canada between 2005 and 2010. These data were collected using Flux-gate proton precession magnetometers and the Flux- Adjusting surface data assimilation system with flight-line space of 0.1 km, tie line space of 0.5 km and terrain clearance ranging from 0.08\u0026ndash;0.1 km along 826,000 lines. The observed potential field data were of very high resolution when likened to the 1970 aero-geophysical data. These recent potential field data were noticed to be suited for mineral and petroleum investigations as well as geological mapping (Ekpo et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2024\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eThe International Geomagnetic Reference Field (IGRF) correction was applied to the magnetic data set to remove the regional component of the Earth's magnetic field, while isolating the local magnetic anomalies that are of interest in geophysical exploration. The IGRF is a mathematical model that represents the Earth's main magnetic field, which is largely generated by processes in the Earth's core. This model is updated every five years and provides the expected magnetic field at any location on the Earth's surface. The IGRF correction involves calculating the magnetic field using the IGRF model at the survey locations and subtracting this regional field from the observed data. This leaves the residual magnetic anomalies, which are more directly related to local geological features. The data used for this study were processed to the form of Total magnetic gridded data displayed as imageries in colour raster format (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eReduction to Equator \u003cb\u003e(\u003c/b\u003eRTE) being a processing technique used to simplify the interpretation of magnetic data by centering magnetic anomalies directly over their causative bodies was applied to the data. Magnetic anomalies can appear skewed or offset due to the inclination and declination of the Earth's magnetic field, particularly at lower latitudes. The RTP mathematically transforms the observed magnetic data to simulate what it would look like if the Earth's magnetic field were vertical (as it is at the magnetic poles or equator). The process involved adjusting both the amplitude and the phase of the magnetic field components. The resulting RTP data have anomalies that are centered over their sources, making it easier to correlate magnetic anomalies with subsurface structures.\u003c/p\u003e \u003cp\u003eResidual-Regional separation was further carried out on the RTP map and the resultant residual map was used for this analysis. The map was divided into 40 overlapping spectral blocks (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) and spectral analysis was carried for each of the blocks.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Methodology\u003c/h2\u003e \u003cp\u003eTo estimate the Curie point (basal) depth \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Z}_{b}\\)\u003c/span\u003e\u003c/span\u003e of the magnetic source, Tanaka et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1999\u003c/span\u003e) assumed the magnetic source layer extends infinitely in all horizontal directions. They considered the depth to be proportional to the horizontal scale of the magnetic source, with the magnetization M(x,y) being a random function of x and y. Blakely (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) demonstrated that the power density spectra of the total field anomaly P is given by:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:P\\left({k}_{x},{k}_{y}\\right)=P({k}_{x},{k}_{y})\\times\\:F({k}_{x},{k}_{y})$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:F\\left({k}_{x},{k}_{y}\\right)=4{\\pi\\:}^{2}{C}_{m}^{2}{\\left|{\\theta\\:}_{m}\\right|}^{2}{\\left|{\\theta\\:}_{f}\\right|}^{2}{e}^{-2\\left|k\\right|{Z}_{t}}{\\left[1-{e}^{-\\left|k\\right|({Z}_{b}-{Z}_{t})}\\right]}^{2}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u0026#119875; is the power density spectrum of the Magnetization, \u0026#119862;\u003csub\u003e\u0026#119898;\u003c/sub\u003e is proportionality constant, \u0026#120579;\u003csub\u003e\u0026#119898;\u003c/sub\u003e and \u0026#120579;\u003csub\u003e\u0026#119891;\u003c/sub\u003e are factors for magnetization and geomagnetic field direction respectively, \u0026#119885;\u003csub\u003e\u0026#119887;\u003c/sub\u003e \u0026#119886;\u0026#119899;\u0026#119889; \u0026#119885;\u003csub\u003e\u0026#119905;\u003c/sub\u003e being the depths to the bottom and top of the magnetic source respectively. The equation can be simplified by noting that all terms except |\u0026#120579;\u003csub\u003e\u0026#119898;\u003c/sub\u003e|\u003csup\u003e2\u003c/sup\u003e \u0026#119886;\u0026#119899;\u0026#119889; |\u0026#120579;\u003csub\u003e\u0026#119891;\u003c/sub\u003e|\u003csup\u003e2\u003c/sup\u003e are radially symmetric. Furthermore, the radial averages of \u0026#120579;\u003csub\u003e\u0026#119898;\u003c/sub\u003e \u0026#119886;\u0026#119899;\u0026#119889; \u0026#120579;\u003csub\u003e\u0026#119891;\u003c/sub\u003e are constants. If (\u0026#119909;,) is completely random and uncorrelated, (\u0026#119896;\u0026#119909;,) is a constant. Hence, the radial average of P is:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:P\\left(\\left|k\\right|\\right)=A{e}^{-2\\left|k\\right|{Z}_{t}}{\\left[1-{e}^{-\\left|k\\right|({Z}_{b}-{Z}_{t})}\\right]}^{2}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere A is a constant and k is the wave number. For wavelengths less than about twice the thickness of the layer Eq.\u0026nbsp;(\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) can be written as Eq.\u0026nbsp;(\u003cspan refid=\"Equ4\" class=\"InternalRef\"\u003e4\u003c/span\u003e)\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}P{\\left|k\\right|}^{1/2}=\\text{ln}B-\\left|k\\right|{Z}_{t}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere B is a constant. The upper bound of magnetic source \u0026#119885;\u003csub\u003e\u0026#119905;\u003c/sub\u003e could be estimated by fitting a straight line through the high-wave number part of a radially average power spectrum \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:[\\text{ln}P{\\left|k\\right|}^{1/2}]\\)\u003c/span\u003e\u003c/span\u003e\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}P{\\left|k\\right|}^{1/2}=C{e}^{-\\left|k\\right|{Z}_{0}}({e}^{-\\left|k\\right|{Z}_{t}-{Z}_{0}}-{e}^{-\\left|k\\right|{Z}_{b}-{Z}_{0}})$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere C is a constant, a long wavelength, Eq.\u0026nbsp;(\u003cspan refid=\"Equ5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) can be rewritten as;\u003cdiv id=\"Equ6\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}P{\\left|k\\right|}^{1/2}=C{e}^{-\\left|k\\right|{Z}_{0}}({e}^{-\\left|k\\right|(-s)}-{e}^{-\\left|k\\right|\\left(s\\right)})\\approx\\:C{e}^{-\\left|k\\right|{Z}_{0}}2\\left|k\\right|s$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere 2 S is the thickness of the magnetic source. From Eq.\u0026nbsp;(\u003cspan refid=\"Equ6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), it can be concluded that;\u003cdiv id=\"Equ7\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}(\\frac{P{\\left|k\\right|}^{1/2}}{\\left|k\\right|})=\\text{ln}D-\\left|k\\right|{Z}_{0}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere D is a constant. The centroid of the magnetic source \u0026#119885;\u003csub\u003e\u0026#119900;\u003c/sub\u003e can be estimated by fitting a straight line through the lower-wave number part of the radially average frequency scale power spectrum average power Then the Basal Depth \u0026#119885;\u003csub\u003e\u0026#119887;\u003c/sub\u003e of the magnetic source will be calculated\u003c/p\u003e \u003cp\u003efrom the equation,\u003cdiv id=\"Equ8\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$\\:{Z}_{b}=2{Z}_{0}-{Z}_{t}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e\u0026#119885;\u003csub\u003e\u0026#119874;\u003c/sub\u003e is the centriod of the magnetic source is the depth to the top of the magnetic source, while \u0026#119885;\u003csub\u003e\u0026#119887;\u003c/sub\u003e is the basal depth of the magnetic sources assumed to be the Curie point depth (Bhattacharyya and Lue, 1975; Okubo et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1985\u003c/span\u003e). At the basal depth \u0026#119885;\u003csub\u003e\u0026#119887;\u003c/sub\u003e ferromagnetic minerals transition into paramagnetic minerals due to reaching a critical temperature of approximately 580\u0026deg;C at that depth. This temperature marks the Curie point, where the magnetic properties of minerals fundamentally change. Hence, the fundamental principle governing conductive heat transport in this context is Fourier's law of heat conduction and it states that the heat flow through a material is proportional to the negative gradient of temperature and can be expressed mathematically as:\u003cdiv id=\"Equ9\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ9\" name=\"EquationSource\"\u003e\n$$\\:q=-k\\frac{dT}{dZ}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere q is the heat flux measured in units of energy with SI unit of W/m\u003csup\u003e2\u003c/sup\u003e, k being the coefficient of thermal conductivity which is a measure of how easily heat flows through a material, with SI unit of \u0026#119882;\u0026#119898;\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u0026#119870;\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u0026#119900;\u0026#119903; \u0026#119882;\u0026#119898;\u003csup\u003e\u0026minus;1\u003c/sup\u003e℃\u003csup\u003e\u0026minus;1\u003c/sup\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:dT/dZ\\)\u003c/span\u003e\u003c/span\u003e is the temperature gradient. .\u003c/p\u003e \u003cp\u003eTanaka et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1999\u003c/span\u003e) demonstrated that the depth of a thermal isotherm, such as the Curie point, is inversely proportional to the heat flow. This relationship implies that higher heat flow results in a shallower isotherm depth, while lower heat flow leads to a deeper isotherm. Under the assumptions of a one-dimensional heat conduction model, where the temperature variation occurs solely in the vertical direction and the temperature gradient \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:dT/dZ\\)\u003c/span\u003e\u003c/span\u003e remains constant, Fourier's law simplifies to:\u003cdiv id=\"Equ10\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ10\" name=\"EquationSource\"\u003e\n$$\\:{Z}_{b}=\\frac{T}{q}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e10\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Z}_{b}\\)\u003c/span\u003e\u003c/span\u003e is the basal depth, T is the temperature at depth \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Z}_{b}\\)\u003c/span\u003e\u003c/span\u003e (typically the Curie temperature, around 580\u0026deg;C) and q the heat flow.\u003c/p\u003e \u003cp\u003eIn this simplified model, the constancy of the temperature gradient implies that the temperature changes linearly with depth. Thus, by understanding the thermal conductivity and the heat flow in the region, one can estimate the depth at which significant thermal transformations, such as the Curie point transition, occur.\u003c/p\u003e \u003cp\u003eHence the thermal gradient is given as;\u003cdiv id=\"Equ11\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ11\" name=\"EquationSource\"\u003e\n$$\\:\\frac{dT}{dZ}=\\frac{{T}_{c}-{T}_{s}}{{Z}_{b}}=\\frac{580℃-{T}_{s}}{{Z}_{b}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e11\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u0026#119879;\u003csub\u003e\u0026#119904;\u003c/sub\u003e is the temperature at the surface. The Heat Flow values were calculated using Eq.\u0026nbsp;(\u003cspan refid=\"Equ12\" class=\"InternalRef\"\u003e12\u003c/span\u003e)\u003cdiv id=\"Equ12\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ12\" name=\"EquationSource\"\u003e\n$$\\:q=k\\left(\\frac{dT}{dZ}\\right)=k\\left(\\frac{580℃-{T}_{s}}{{Z}_{b}}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e12\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere q is the heat flow and k the coefficient of thermal conductivity. The k value might differs within the study area due to variation in the different rock units that are within the study area. The mean value for the coefficient of thermal conductivity in the study area varies depending on the specific geological formations and types of rocks present. However, for sedimentary basins like the Niger Delta, typical values for thermal conductivity generally range between 1.5 to 3.5 Wm\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003eC\u003csup\u003e\u0026minus;1\u003c/sup\u003e. For instance, in sedimentary rocks commonly found in the Niger Delta such as sandstones and shales, the thermal conductivity is often around 2.5\u0026ndash;3.5 Wm\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003eC\u003csup\u003e\u0026minus;1\u003c/sup\u003e for sandstones and 1.5\u0026ndash;2.5 Wm\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003eC\u003csup\u003e\u0026minus;1\u003c/sup\u003e for shales (Obande \u0026amp; Ojo, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Onwuemesi \u0026amp; Oha, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The thermal conductivity of 2.5 Wm\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003eC\u003csup\u003e\u0026minus;1\u003c/sup\u003e was used in this work.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe first result obtained are those of the spectral plot shown in Fig.\u0026nbsp;5, just a sample because all the results for depth to top (Z\u003csub\u003et\u003c/sub\u003e) and depth to centroid (Z\u003csub\u003eo\u003c/sub\u003e) obtained from the plots, Curie Point Depth (Z\u003csub\u003eb\u003c/sub\u003e), geothermal gradient (GTG) and Heat flow (HF) obtain from the use of equations \u003cspan refid=\"Equ8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, \u003cspan refid=\"Equ9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and \u003cspan refid=\"Equ10\" class=\"InternalRef\"\u003e10\u003c/span\u003e respectively also presented on Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results presented on Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e was harnessed and used to processed the maps of depth to bottom (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), geothermal gradient (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e) and heat flow shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e. \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFigure 5\u003c/strong\u003e \u003cp\u003eTotal magnetic intensity (TMI) map\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCalculated Average Curie point depth, Geothermal gradient and Heat flow from Spectral analysis from total magnetic intensity (TMI) map\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBlock\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLONGITUDE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLATITUDE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDepth to Centriod\u003c/p\u003e \u003cp\u003eZ\u003csub\u003eo\u003c/sub\u003e (Km)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDepth to top\u003c/p\u003e \u003cp\u003eZ\u003csub\u003et\u003c/sub\u003e (Km)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCurie point depth Z\u003csub\u003eb\u003c/sub\u003e (Km)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGeothermal gradient\u003c/p\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\varvec{d}\\varvec{T}}{\\varvec{d}\\varvec{z}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003e(\u003csup\u003eo\u003c/sup\u003eC/Km)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eHeat flow\u003c/p\u003e \u003cp\u003eQ (mWm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e68.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e55.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e26.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e61.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e23.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e 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colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e33.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e17.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e43.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e 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colname=\"c8\"\u003e \u003cp\u003e20.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e52.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e11.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e27.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e77.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e18.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e83.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e17.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e35.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e69.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e66.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e33.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e66.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e51.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e11.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAVERAGE\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e60.36\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e10.30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e25.74\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eThe Curie Point Depth (CPD) Map (\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) which indicate the depth at which the magnetic anomaly loses its magnetism at Curie temperature (\u0026#119879;\u0026#119888;) has it lowest and highest values as 23.27 km (Block 9) and 83.15 km (Block 36) respectively with an average depth of 60.36 km.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eThe Geothermal Gradient Map (\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e shows the rate of depth dependent temperature growth ranging between 6.98 ℃\u0026#119896;\u0026#119898;\u003csup\u003e\u0026minus;1\u003c/sup\u003e to 24.93 ℃\u0026#119896;\u0026#119898;\u003csup\u003e\u0026minus;1\u003c/sup\u003ewith an average value of 10.30 ℃\u0026#119896;\u0026#119898;\u003csup\u003e\u0026minus;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eThe Heat Flow\u003c/b\u003e values ranges between 17.44 \u0026#119898;\u0026#119882;\u0026#119898;\u003csup\u003e\u0026minus;2\u003c/sup\u003e to 62.33 \u0026#119898;\u0026#119882;\u0026#119898;\u003csup\u003e\u0026minus;2 1\u003c/sup\u003ewith an average value of 25.74 \u0026#119898;\u0026#119882;\u0026#119898;\u003csup\u003e\u0026minus;2\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Curie Point Depth and Its Geological Implications\u003c/h2\u003e \u003cp\u003eThe Curie point depth is a key thermal marker in understanding the subsurface temperature distribution. It refers to the depth at which magnetic minerals lose their magnetism due to reaching a critical temperature, typically around 580\u0026deg;C. This depth can also provide indirect insights into the geothermal gradient and overall heat flow in the crust, which are essential factors in hydrocarbon maturation.\u003c/p\u003e \u003cp\u003eIn the Niger Delta Basin, the temperature profile with depth controls the maturation of organic matter into oil and gas. The oil window, generally between 60\u0026deg;C and 120\u0026deg;C, is the temperature range within which organic-rich sediments begin to generate hydrocarbons, while the gas window occurs at higher temperatures, generally above 120\u0026deg;C to around 200\u0026deg;C. The deeper the Curie point, the cooler the subsurface thermal regime, and the less likely it is for organic matter to mature into hydrocarbons at accessible depths. Conversely, shallow Curie points suggest a more thermally active crust, potentially leading to faster maturation of hydrocarbons, and, in some cases, over-maturation, where oil is converted to gas or lost due to excessive heat.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Mature Regions for Hydrocarbon Exploration\u003c/h2\u003e \u003cp\u003eMature regions, where the thermal conditions are optimal for hydrocarbon generation without pushing the organic matter into over-maturation, are particularly important for both oil and gas exploration. In the attached data, certain blocks such as Block 2, Block 4, Block 7, and Block 29 demonstrate this balance. These blocks have Curie depths that range between 55.44 km and 62.60 km, which, when coupled with geothermal gradients of approximately 9.32\u0026deg;C/km to 10.17\u0026deg;C/km, indicate a stable subsurface environment conducive to oil and gas maturation.\u003c/p\u003e \u003cp\u003eIn these areas, the heat flow is moderate, ranging from 23.16 mW/m\u0026sup2; to 25.41 mW/m\u0026sup2;, reflecting a consistent, moderate input of thermal energy from the Earth\u0026rsquo;s interior. This suggests that organic-rich sediments located in these regions are likely to have reached the temperatures necessary for oil and possibly early-stage gas generation, without the risk of over-maturation. Geologically, these areas might be located in the central or tectonically stable parts of the basin where sedimentation rates and heat flow have balanced out over time, creating ideal conditions for hydrocarbon preservation and maturation. In the context of the Niger Delta, these blocks represent regions where exploration is likely to yield mature hydrocarbons, particularly oil, due to the moderate subsurface heating.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Over-Matured Regions for Hydrocarbon Exploration\u003c/h2\u003e \u003cp\u003eIn contrast, over-matured regions are characterized by very shallow Curie depths, high geothermal gradients, and elevated heat flow, which together indicate a much more thermally dynamic subsurface. In the attached data, Blocks 8, 9, and 18 stand out as over-matured zones. Block 9, for instance, has an extremely shallow Curie depth of 23.27 km, accompanied by a high geothermal gradient of 24.93\u0026deg;C/km and a heat flow of 62.33 mW/m\u0026sup2;. These thermal conditions suggest that the subsurface in this region has experienced excessive heating, driving the maturation of hydrocarbons beyond the oil window and into the gas window or, in extreme cases, leading to the thermal degradation of hydrocarbons.\u003c/p\u003e \u003cp\u003eThe high heat flow in these blocks may be attributed to localized tectonic or magmatic activity, which could introduce additional heat into the system. In the Niger Delta, such zones may be associated with faulting or other tectonic processes that bring deeper, hotter materials closer to the surface. In over-mature regions, the potential for oil exploration diminishes, as the elevated temperatures likely caused any oil to be over-cooked into gas or possibly burned off entirely. However, these areas may still hold significant gas reserves, as the high thermal gradients would have facilitated the cracking of oil into natural gas. Thus, these blocks are more suited for gas exploration, with Block 9, in particular, presenting a strong candidate for further investigation into gas reservoirs.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Under-Matured Regions for Hydrocarbon Exploration\u003c/h2\u003e \u003cp\u003eOn the opposite end of the spectrum, under-matured regions are characterized by deep Curie point depths, low geothermal gradients, and correspondingly low heat flow, resulting in cooler subsurface conditions. Blocks such as Block 36, Block 19, Block 32, and Block 35 fit into this category, with Block 36 having a particularly deep Curie depth of 83.15 km, a low geothermal gradient of 6.98\u0026deg;C/km, and a heat flow of only 17.44 mW/m\u0026sup2;. These regions represent parts of the basin where the organic material has not yet been exposed to sufficient temperatures to generate hydrocarbons in commercial quantities.\u003c/p\u003e \u003cp\u003eGeologically, under-matured regions in the Niger Delta are often associated with tectonically stable, cooler areas, possibly situated farther from the heat-generating influences of tectonic activity or magmatic intrusions. These areas are more likely to be found in the deeper, older sections of the basin where the thermal regime has remained relatively cool over geologic time scales. In these zones, the organic material is preserved but remains immature, meaning that it has not yet undergone the necessary thermal transformation into hydrocarbons. Exploration in such areas might yield little in the way of immediate hydrocarbon production, but they could represent future prospects if tectonic or magmatic activity were to increase the regional heat flow, thus maturing the organic material into oil or gas over time.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Implications for Hydrocarbon Exploration in the Niger Delta\u003c/h2\u003e \u003cp\u003eThe variation in Curie point depth, geothermal gradient, and heat flow across the study area reflects the heterogeneity of the subsurface thermal regime in the Niger Delta Basin. Regions with moderate Curie depths and geothermal gradients, such as Blocks 2, 4, 7, and 29, are prime candidates for oil exploration, as they provide the optimal thermal conditions for hydrocarbon maturation without the risk of over-maturation. These blocks represent areas where the thermal regime has allowed organic-rich sediments to transform into oil and possibly early-stage gas, making them highly attractive targets for exploration.\u003c/p\u003e \u003cp\u003eIn contrast, blocks such as 8, 9, and 18, which exhibit shallow Curie depths, high geothermal gradients, and elevated heat flow, are more suited for gas exploration. These regions have likely experienced excessive heat, pushing hydrocarbons beyond the oil window into the gas window. The thermal conditions in these blocks are consistent with rapid maturation and gas generation, making them ideal for gas-focused exploration strategies.\u003c/p\u003e \u003cp\u003eFinally, under-matured regions such as Blocks 36, 19, and 35 are cooler and less thermally evolved. These regions may contain large amounts of organic material that have not yet matured into hydrocarbons due to insufficient heating. While these areas may not be immediate targets for exploration, they could represent long-term prospects if heat flow increases or if alternative exploration techniques, such as enhanced geothermal energy, become viable.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe Curie point depth, geothermal gradient, and heat flow data from the attached study provide crucial insights into the hydrocarbon maturity of different parts of the study area, which can be extended to the Niger Delta Basin. Mature areas, such as those in blocks 2, 4, 7, and 29, are likely to offer the best potential for oil exploration due to their balanced thermal regime. Over-matured areas, particularly blocks 8, 9, and 18, are more suitable for gas exploration, as the intense heat flow has likely driven oil to over-mature into gas. Under-matured regions, like blocks 19, 32, and 36, are currently too cool for significant hydrocarbon generation and represent areas where further heat input may be needed to mature the organic material into hydrocarbons.\u003c/p\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Recommendation\u003c/h2\u003e \u003cp\u003eThe following recommendation have been proposed from these studies:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eFocus Oil Exploration in Moderately Mature Regions: Blocks with moderate Curie point depths (55\u0026ndash;62 km) and geothermal gradients (9\u0026ndash;10\u0026deg;C/km), such as Blocks 2, 4, 7, and 29, are optimal for oil exploration as they provide favorable thermal conditions for hydrocarbon maturation.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePrioritize Gas Exploration in Over-Matured Zones: Blocks with shallow Curie depths and high geothermal gradients, such as Block 9, should be prioritized for gas exploration due to their thermally active subsurface, which has likely pushed hydrocarbons beyond the oil window into gas.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eConsider Long-Term Potential of Under-Matured Areas: Blocks with deep Curie points and low geothermal gradients, such as Block 36, are currently under-mature for hydrocarbons but may represent future opportunities if heat flow increases or alternative exploration techniques become viable.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eGeophysical Monitoring: Continuous geophysical monitoring of the study area is recommended to track thermal evolution and tectonic activity, which could alter the thermal maturity of hydrocarbons over time.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e. The author declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHUMAN ANIMAL RIGHTS:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis article does not contain studies with human or animal subject.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAjakaiye, D. E. (1985). Geothermal gradients in Nigeria and their implications for petroleum exploration. Journal of African Earth Sciences, 3(3), 511-520.\u003c/li\u003e\n\u003cli\u003eAjao, K. R., Ayodele, T. R., \u0026amp; Jegede, O. O. (2016). An assessment of the geothermal potential of the Niger Delta using oil and gas well temperature data. Renewable Energy, 85, 717-725.\u003c/li\u003e\n\u003cli\u003eBhattacharyya, B. K., \u0026amp; Leu, L. K. (1975). Analysis of magnetic anomalies over Yellowstone National Park: Mapping of Curie point isothermal surface for geothermal reconnaissance. Journal of Geophysical Research, 80(32), 4461-4465.\u003c/li\u003e\n\u003cli\u003eBlakely, R. J. (1995). Potential Theory in Gravity and Magnetic Applications. Cambridge University Press.\u003c/li\u003e\n\u003cli\u003eCorredor, F., Shaw, J. H., \u0026amp; Bilotti, F. (2005). Structural styles in the deep-water fold and thrust belts of the Niger Delta. American Association of Petroleum Geologists Bulletin, 89(6), 753-780.\u003c/li\u003e\n\u003cli\u003eDoust, H. (1990). Petroleum geology of the Niger Delta. Geological Society, London, Special Publications, 50(1), 365-372.\u003c/li\u003e\n\u003cli\u003eDoust, H., and Omatsola, E. (1990). Niger Delta: American Association of Petroleum Geologists Memoir 48.\u003c/li\u003e\n\u003cli\u003eEkine, A. S., \u0026amp; Iyabe, P. E. (2009). Heat flow studies in the Niger Delta basin. Geothermal Energy, 34(4), 523-531.\u003c/li\u003e\n\u003cli\u003eEkpo A. E., BasseyN. E., George N. J. (2024). Aero-gravity data analysis for delineating possible channels of mineralizations migration through lineament. A case study of Southeastern Niger Delta, Nigeria. AKSU Annels of Sustainable Development 2(1), 139-168, 2024. https://doi.org/10.60787/AASD-v2i1-35. \u003c/li\u003e\n\u003cli\u003eEkpo, A. E., Bassey, N. E., George, N. J., \u0026amp; Udo, I. G. (2024). Depth to basement estimation from aerogravity data over the Southeastern part of Niger Delta region of Nigeria. \u003cem\u003eResearchers Journal of Science and Technology\u003c/em\u003e, \u003cem\u003e4\u003c/em\u003e(5), 44\u0026ndash;66. Retrieved from https://rejost.com.ng/index.php/home/article/view/135\u003c/li\u003e\n\u003cli\u003eEvamy, B. D., Haremboure, J., Kamerling, P., Knaap, W. A., Molloy, F. A., \u0026amp; Rowlands, P. H. (1978). Hydrocarbon habitat of the Tertiary Niger Delta. American Association of Petroleum Geologists Bulletin, 62(1), 1-39.\u003c/li\u003e\n\u003cli\u003eFatoke, A. O. (2010). Sequence stratigraphic framework of the paralic Agbada Formation, Northern depobelt, onshore Niger Delta, Nigeria. PhD Dissertation, University of Texas at Dallas.\u003c/li\u003e\n\u003cli\u003eLehner, P., \u0026amp; De Ruiter, P. A. C. (1977). Structural history of Atlantic Margin of Africa. American Association of Petroleum Geologists Bulletin, 61(7), 961-981.\u003c/li\u003e\n\u003cli\u003eMerki, P. J. (1972). Structural geology of the Cenozoic Niger Delta. First Conference on African Geology, Ibadan, Nigeria, 635-646.\u003c/li\u003e\n\u003cli\u003eOkiwelu, A. A., Adebayo, O. E., \u0026amp; Onyemesili, M. N. (2013). Sedimentology and sequence stratigraphy of the western Niger Delta. Nigerian Journal of Science, 47(1), 81-102.\u003c/li\u003e\n\u003cli\u003eOkubo, Y., Graf, R. J., Hansen, R. O., Ogawa, K., \u0026amp; Tsu, H. (1985). 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The Niger Delta Petroleum System: Niger Delta Province, Nigeria, Cameroon, and Equatorial Guinea, Africa. US Geological Survey Bulletin, 2207-B.\u003c/li\u003e\n\u003cli\u003eWhiteman, A. J. (1982). Nigeria: Its Petroleum Geology, Resources and Potential. Graham \u0026amp; Trotman.\u003c/li\u003e\n\u003cli\u003eNigerian Meteorological Agency (NIMET). (2023). Climate Data and Reports. Retrieved from [NIMET website](https://www.nimet.gov.ng).\u003c/li\u003e\n\u003cli\u003eObande, E. G., \u0026amp; Ojo, S. B. (2008). Thermal conductivity and heat flow estimates in parts of the Niger Delta, Nigeria. Journal of African Earth Sciences, 50(2-3), 164-170.\u003c/li\u003e\n\u003cli\u003eOnwuemesi, A. G., \u0026amp; Oha, I. A. (2008). Geothermal gradients and subsurface temperature variations in parts of the Niger Delta Basin, Nigeria. Geothermics, 37(4), 476-484.\u003c/li\u003e\n\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"acta-geophysica","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"agph","sideBox":"Learn more about [Acta Geophysica](http://link.springer.com/journal/11600)","snPcode":"11600","submissionUrl":"https://www.editorialmanager.com/agph/default2.aspx","title":"Acta Geophysica","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Curie temperature, Hydrocarbon Maturation, Niger Delta Basin, Oil and Gas Exploration","lastPublishedDoi":"10.21203/rs.3.rs-5194917/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5194917/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study focuses on the Curie point depth (CPD) as a critical factor in determining the hydrocarbon potential of the southeastern Niger Delta Basin, using aeromagnetic data to analyze subsurface thermal structures. The Curie point depth, which marks the depth at which ferromagnetic minerals lose their magnetic properties at a temperature of approximately 580\u0026deg;C, varies across the basin from 23.27 km to 83.15 km, with an average of 60.36 km. These variations in CPD, combined with geothermal gradient values ranging from 6.98\u0026deg;C/km to 24.93\u0026deg;C/km, and heat flow measurements between 17.44 mW/m\u0026sup2; and 62.33 mW/m\u0026sup2;, provide insights into the thermal maturity of hydrocarbons in different regions. The findings indicate that blocks with intermediate CPD values, such as Blocks 2, 4, 7, and 29, with depths between 55.44 km and 62.60 km, are conducive to oil exploration due to their balanced thermal regimes. Conversely, blocks with shallow CPD values, like Block 9 (23.27 km), exhibit higher heat flow and geothermal gradients, making them better suited for gas exploration due to over-maturation of hydrocarbons. In contrast, deeper CPD regions, like Block 36 (83.15 km), reflect under-mature conditions, where hydrocarbon formation has not yet reached optimal levels. This study underscores the importance of CPD in guiding hydrocarbon exploration strategies in the Niger Delta Basin.\u003c/p\u003e","manuscriptTitle":"Curie Point Depth as a Key Indicator of Hydrocarbon Maturity in the Southeastern Niger Delta Basin: Insights From Aeromagnetic Data","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-13 13:14:44","doi":"10.21203/rs.3.rs-5194917/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-11-10T16:17:38+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-01T06:20:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Acta Geophysica","date":"2024-10-31T09:05:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-30T20:56:37+00:00","index":"","fulltext":""},{"type":"submitted","content":"Acta Geophysica","date":"2024-10-29T06:20:49+00:00","index":"","fulltext":""},{"type":"decision","content":"Major revisions","date":"2024-10-17T03:16:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"acta-geophysica","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"agph","sideBox":"Learn more about [Acta Geophysica](http://link.springer.com/journal/11600)","snPcode":"11600","submissionUrl":"https://www.editorialmanager.com/agph/default2.aspx","title":"Acta Geophysica","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"035b1927-e6f3-4906-a5de-a28775f05e8b","owner":[],"postedDate":"November 13th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2025-03-16T11:26:44+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-13 13:14:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5194917","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5194917","identity":"rs-5194917","version":["v1"]},"buildId":"cBFmMYwuxLRRLfASyISRj","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}