Low-density workover fluid technology designed to lower the required sealing strength for operations in the fractured reservoirs of the Ordos Basin

Low-density workover fluid technology designed to lower the required sealing strength for operations in the fractured reservoirs of the Ordos Basin | 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 Article Low-density workover fluid technology designed to lower the required sealing strength for operations in the fractured reservoirs of the Ordos Basin Wang Yue¹, Liu Guoliang¹, Yang Boli¹, Yuwen Xihan¹, Zhai Xiaopeng², and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8277337/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 10 You are reading this latest preprint version Abstract The tight Upper Paleozoic sandstone reservoirs and Lower Paleozoic carbonate reservoirs in the Ordos Basin necessitate fracturing or acidizing to generate artificial fractures prior to production, classifying them as typical fractured reservoirs. During workover operations, the depletion of formation pressure results in a considerable loss pressure differential. Conventional sealing operations impose overly stringent requirements on plugging materials, giving rise to substantial risks of formation damage and slow post - workover production recovery rates. Laboratory investigations identified optimized components: modified lauramidopropyl betaine as the foaming agent, alcohol - ether modified polyhydroxy polymer as the foam stabilizer, modified hydroxyethyl starch as the viscosifier, and a xanthan gum derivative as the stabilizer. Aiming at a base fluid density of 0.85 - 0.95 g/cm³, an orthogonal experimental design produced a basic formula: (0.80 - 1.40%) viscosifier+(0.5 - 0.6%) stabilizer+(0.18 - 0.32%) foaming agent+(0.28 - 0.32%) foam stabilizer. Glass microspheres with a D90 particle size ≤70 μm, a density of 0.42 - 0.44 g/cm³, and a compressive strength ≥40 MPa were selected as the low - density particles. A low - density workover fluid system with an adjustable density range of 0.65 - 0.90 g/cm³ was developed. Laboratory tests indicated that increasing the low - density particle concentration from 0% to 50% led to a reduction in the system density from 0.85 g/cm³ to 0.65 g/cm³. After static aging for 48 hours at room temperature and 90°C, the density increments were less than 0.05 g/cm³ and 0.10 g/cm³ respectively. After repeated stirring at 3000 r/min for 5 minutes, the density increments were less than 0.01 g/cm³ and 0.03 g/cm³ respectively, demonstrating stable density under reservoir temperature conditions. Five fluid samples with densities ranging from 0.65 - 0.85 g/cm³ were injected at a constant rate of 0.5 mL/min into artificial fractures 0.1 mm wide. The pressure increase relative to water displacement ranged from 6.20 to 17.15 MPa, with lower - density fluids exhibiting higher pressure increases, indicating enhanced plugging performance with decreasing density. After plugging the core samples, 1.5 pore volumes of a 1% ammonium persulfate solution were directly injected and allowed to soak for 2 hours to break the gel. The measured core permeability recovery rate ranged from 92.48% to 95.56%, demonstrating excellent formation protection. Field applications in two low - pressure gas wells, G - X and SN - X, completed in the tight Shanxi Formation sandstone and Majiagou Formation carbonate reservoirs with pressure coefficients of 0.76 and 0.43 respectively, involved the injection of 53.5 m³ and 34.3 m³ of the low - density workover fluid (densities 0.76 g/cm³ and 0.75 g/cm³). Fluid returns were observed at the wellhead with a loss rate below 0.01 m³/h. After workover, gas lift was directly initiated for fluid recovery. The post - workover gas production recovery rate reached 95.83% to 130%. This study confirms that the low - density workover fluid, by reducing the fluid column pressure in the wellbore, effectively mitigates the pressure burden on the fractured formation. This addresses the limitation of inadequate formation protection caused by excessive plugging strength during conventional workover operations. Physical sciences/Energy science and technology Physical sciences/Engineering Physical sciences/Materials science Earth and environmental sciences/Solid earth sciences Natural Gas Fractured Reservoir Workover Lost Circulation Control Low-Density Workover Fluid Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 12 Jan, 2026 Reviews received at journal 19 Dec, 2025 Reviews received at journal 11 Dec, 2025 Reviewers agreed at journal 10 Dec, 2025 Reviewers agreed at journal 10 Dec, 2025 Reviewers invited by journal 09 Dec, 2025 Editor assigned by journal 09 Dec, 2025 Editor invited by journal 09 Dec, 2025 Submission checks completed at journal 08 Dec, 2025 First submitted to journal 08 Dec, 2025 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. We do this by developing innovative software and high quality services for the global research community. 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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-8277337","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":559203654,"identity":"026273e1-5fcf-44b6-a6fb-9bd941940bcc","order_by":0,"name":"Wang Yue¹","email":"","orcid":"","institution":"Changqing Downhole Operation Company, CNPC Chuanqing Drilling Engineering Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Wang","middleName":"","lastName":"Yue¹","suffix":""},{"id":559203660,"identity":"4d17e120-0dd1-4ac9-8332-c8e79aa9eb3c","order_by":1,"name":"Liu 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Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Natural Gas, Fractured Reservoir, Workover, Lost Circulation Control, Low-Density Workover Fluid","lastPublishedDoi":"10.21203/rs.3.rs-8277337/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8277337/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe tight Upper Paleozoic sandstone reservoirs and Lower Paleozoic carbonate reservoirs in the Ordos Basin necessitate fracturing or acidizing to generate artificial fractures prior to production, classifying them as typical fractured reservoirs. During workover operations, the depletion of formation pressure results in a considerable loss pressure differential. Conventional sealing operations impose overly stringent requirements on plugging materials, giving rise to substantial risks of formation damage and slow post - workover production recovery rates.\u003c/p\u003e\n\u003cp\u003eLaboratory investigations identified optimized components: modified lauramidopropyl betaine as the foaming agent, alcohol - ether modified polyhydroxy polymer as the foam stabilizer, modified hydroxyethyl starch as the viscosifier, and a xanthan gum derivative as the stabilizer. Aiming at a base fluid density of 0.85 - 0.95 g/cm³, an orthogonal experimental design produced a basic formula: (0.80 - 1.40%) viscosifier+(0.5 - 0.6%) stabilizer+(0.18 - 0.32%) foaming agent+(0.28 - 0.32%) foam stabilizer. Glass microspheres with a D90 particle size ≤70 μm, a density of 0.42 - 0.44 g/cm³, and a compressive strength ≥40 MPa were selected as the low - density particles. A low - density workover fluid system with an adjustable density range of 0.65 - 0.90 g/cm³ was developed.\u003c/p\u003e\n\u003cp\u003eLaboratory tests indicated that increasing the low - density particle concentration from 0% to 50% led to a reduction in the system density from 0.85 g/cm³ to 0.65 g/cm³. After static aging for 48 hours at room temperature and 90°C, the density increments were less than 0.05 g/cm³ and 0.10 g/cm³ respectively. After repeated stirring at 3000 r/min for 5 minutes, the density increments were less than 0.01 g/cm³ and 0.03 g/cm³ respectively, demonstrating stable density under reservoir temperature conditions.\u003c/p\u003e\n\u003cp\u003eFive fluid samples with densities ranging from 0.65 - 0.85 g/cm³ were injected at a constant rate of 0.5 mL/min into artificial fractures 0.1 mm wide. The pressure increase relative to water displacement ranged from 6.20 to 17.15 MPa, with lower - density fluids exhibiting higher pressure increases, indicating enhanced plugging performance with decreasing density.\u003c/p\u003e\n\u003cp\u003eAfter plugging the core samples, 1.5 pore volumes of a 1% ammonium persulfate solution were directly injected and allowed to soak for 2 hours to break the gel. The measured core permeability recovery rate ranged from 92.48% to 95.56%, demonstrating excellent formation protection.\u003c/p\u003e\n\u003cp\u003eField applications in two low - pressure gas wells, G - X and SN - X, completed in the tight Shanxi Formation sandstone and Majiagou Formation carbonate reservoirs with pressure coefficients of 0.76 and 0.43 respectively, involved the injection of 53.5 m³ and 34.3 m³ of the low - density workover fluid (densities 0.76 g/cm³ and 0.75 g/cm³). Fluid returns were observed at the wellhead with a loss rate below 0.01 m³/h. After workover, gas lift was directly initiated for fluid recovery. The post - workover gas production recovery rate reached 95.83% to 130%.\u003c/p\u003e\n\u003cp\u003eThis study confirms that the low - density workover fluid, by reducing the fluid column pressure in the wellbore, effectively mitigates the pressure burden on the fractured formation. This addresses the limitation of inadequate formation protection caused by excessive plugging strength during conventional workover operations.\u003c/p\u003e","manuscriptTitle":"Low-density workover fluid technology designed to lower the required sealing strength for operations in the fractured reservoirs of the Ordos Basin","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-15 14:24:06","doi":"10.21203/rs.3.rs-8277337/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-12T05:51:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-19T09:35:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-11T10:24:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"338553846508990387373083648938301377407","date":"2025-12-10T18:59:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"209602291600212046516829696170911000128","date":"2025-12-10T06:04:44+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-10T03:32:12+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-10T03:30:17+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-10T03:21:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-08T09:36:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-12-08T09:23:03+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"49643e1d-c0af-4c16-b73d-68baf43c4f42","owner":[],"postedDate":"December 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":59532484,"name":"Physical sciences/Energy science and technology"},{"id":59532485,"name":"Physical sciences/Engineering"},{"id":59532486,"name":"Physical sciences/Materials science"},{"id":59532487,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2026-01-12T05:54:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-15 14:24:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8277337","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8277337","identity":"rs-8277337","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}