Geochemical controls on colloidal stability and polar compounds deposition in Cretaceous –Tertiary carbonate reservoirs using core extracts, SW Iran

Geochemical controls on colloidal stability and polar compounds deposition in Cretaceous –Tertiary carbonate reservoirs using core extracts, SW Iran | 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 Geochemical controls on colloidal stability and polar compounds deposition in Cretaceous –Tertiary carbonate reservoirs using core extracts, SW Iran Ahmad Batvandi, Ali Shekarifard This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8813846/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Asphaltene instability and precipitation represent major flow-assurance challenges in carbonate reservoirs and are strongly influenced by fluid composition, thermal maturity, and hydrocarbon charge history. Predicting these processes remains difficult because conventional compositional indices often fail to capture the combined effects of active polar compounds and refractory organic matter under heterogeneous reservoir conditions. In this study, we investigate the geochemical controls on asphaltene stability in Cretaceous–Tertiary carbonate reservoirs using an integrated analysis of bulk oil composition, biomarker distributions, and Rock-Eval pyrolysis data derived from reservoir rock bitumen. Rock-Eval pyrolysis was performed on 127 core samples, complemented by biomarker (GC–MS) and SARA compositional analyses (Iatroscan–FID) on 21 core extracts from multiple carbonate reservoirs. The results show that variations in the balance between saturates, aromatics, resins, and asphaltenes exert a primary control on oil colloidal behavior. Depletion of resin and aromatic fractions combined with saturate enrichment promotes colloidal instability and increases the likelihood of asphaltene aggregation. Shallow reservoir intervals display relatively stable colloidal systems, whereas deeper intervals exhibit pronounced instability reflected by elevated colloidal instability indices and reduced polarity indices. Geochemical results indicate that the free oils and bitumen are non-biodegraded and are predominantly derived from marine Type II organic matter with varying levels of thermal maturity. To better characterize polar compound behavior, a composite polar index (CPI) is introduced by integrating generative polar fractions (S2b), refractory organic matter (residual carbon), and reactive organic content derived from Rock-Eval parameters. The CPI effectively discriminates stable, transitional, and critical intervals and identifies zones prone to polar compound accumulation and asphaltene precipitation, including conditions where conventional SARA-based indices show limitations. The results indicate that asphaltene instability is primarily governed by compositional evolution and thermal maturity rather than pressure-related effects alone. This integrated geochemical framework provides a quantitative and transferable approach for predicting asphaltene precipitation risk in heterogeneous carbonate reservoirs. Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Solid earth sciences Asphaltene precipitation colloidal stability SARA analysis Rock-Eval pyrolysis carbonate reservoirs Abadan Plain Iran Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8813846","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":593549385,"identity":"81b73e27-0d6c-4ecd-8558-627a5751dcd1","order_by":0,"name":"Ahmad Batvandi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0klEQVRIiWNgGAWjYFACHih9mPkAhMFMjBaw2sNsCRAG8VoO8BgwHCDGWfwNvAc/f2yzy+M7zvNN+gODnTwDO+8DvFokDvAlSxxsSy6WPMy7TeIAQ7JhAzO7AX5rgO6ROHCGOXEDRAtzAgMzG34d8gd4jH8cOFMP1MLzDKilnrAWgwM8ZhIHKg6DtLABtRwmrMXwMF+axZmK44kzD7MZW5wxOG7YRkiL3PHewzcqDKoT+84ffnijoqJanp//GH4taBEHDCsCdoyCUTAKRsEoIAYAADIbQIAtgdgQAAAAAElFTkSuQmCC","orcid":"","institution":"University of Tehran","correspondingAuthor":true,"prefix":"","firstName":"Ahmad","middleName":"","lastName":"Batvandi","suffix":""},{"id":593549388,"identity":"db7e466b-e060-46e3-ad5b-c019646403d2","order_by":1,"name":"Ali Shekarifard","email":"","orcid":"","institution":"University of Tehran","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"","lastName":"Shekarifard","suffix":""}],"badges":[],"createdAt":"2026-02-07 08:53:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8813846/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8813846/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104400040,"identity":"55bb8b28-afe0-4a08-b149-6786c3edd0ae","added_by":"auto","created_at":"2026-03-11 12:08:38","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1687720,"visible":true,"origin":"","legend":"","description":"","filename":"ManuscriptAsphaltene.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8813846/v1_covered_cc910324-147f-4828-b870-f73398d616aa.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Geochemical controls on colloidal stability and polar compounds deposition in Cretaceous –Tertiary carbonate reservoirs using core extracts, SW Iran","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Asphaltene precipitation, colloidal stability, SARA analysis, Rock-Eval pyrolysis, carbonate reservoirs, Abadan Plain, Iran","lastPublishedDoi":"10.21203/rs.3.rs-8813846/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8813846/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAsphaltene instability and precipitation represent major flow-assurance challenges in carbonate reservoirs and are strongly influenced by fluid composition, thermal maturity, and hydrocarbon charge history. Predicting these processes remains difficult because conventional compositional indices often fail to capture the combined effects of active polar compounds and refractory organic matter under heterogeneous reservoir conditions. In this study, we investigate the geochemical controls on asphaltene stability in Cretaceous\u0026ndash;Tertiary carbonate reservoirs using an integrated analysis of bulk oil composition, biomarker distributions, and Rock-Eval pyrolysis data derived from reservoir rock bitumen. Rock-Eval pyrolysis was performed on 127 core samples, complemented by biomarker (GC\u0026ndash;MS) and SARA compositional analyses (Iatroscan\u0026ndash;FID) on 21 core extracts from multiple carbonate reservoirs. The results show that variations in the balance between saturates, aromatics, resins, and asphaltenes exert a primary control on oil colloidal behavior. Depletion of resin and aromatic fractions combined with saturate enrichment promotes colloidal instability and increases the likelihood of asphaltene aggregation. Shallow reservoir intervals display relatively stable colloidal systems, whereas deeper intervals exhibit pronounced instability reflected by elevated colloidal instability indices and reduced polarity indices.\u003c/p\u003e \u003cp\u003eGeochemical results indicate that the free oils and bitumen are non-biodegraded and are predominantly derived from marine Type II organic matter with varying levels of thermal maturity. To better characterize polar compound behavior, a composite polar index (CPI) is introduced by integrating generative polar fractions (S2b), refractory organic matter (residual carbon), and reactive organic content derived from Rock-Eval parameters. The CPI effectively discriminates stable, transitional, and critical intervals and identifies zones prone to polar compound accumulation and asphaltene precipitation, including conditions where conventional SARA-based indices show limitations. The results indicate that asphaltene instability is primarily governed by compositional evolution and thermal maturity rather than pressure-related effects alone. This integrated geochemical framework provides a quantitative and transferable approach for predicting asphaltene precipitation risk in heterogeneous carbonate reservoirs.\u003c/p\u003e","manuscriptTitle":"Geochemical controls on colloidal stability and polar compounds deposition in Cretaceous –Tertiary carbonate reservoirs using core extracts, SW Iran","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-20 13:54:58","doi":"10.21203/rs.3.rs-8813846/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f246e4ab-fa98-4206-af09-57ea2d76ca67","owner":[],"postedDate":"February 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":63160725,"name":"Earth and environmental sciences/Environmental sciences"},{"id":63160726,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2026-03-02T06:57:12+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-20 13:54:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8813846","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8813846","identity":"rs-8813846","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}