Geochemical Changes and Fracture Development in Woodford Shale Cores Following Hydrous Pyrolysis under Uniaxial Confinement

Abstract

PreviousNext No AccessUnconventional Resources Technology Conference, Denver, Colorado, 12-14 August 2013Geochemical Changes and Fracture Development in Woodford Shale Cores Following Hydrous Pyrolysis under Uniaxial ConfinementAuthors: Justin E. BirdwellMichael D. LewanMichael MillerJustin E. BirdwellU. S. Geological Survey, Denver, COSearch for more papers by this author, Michael D. LewanU. S. Geological Survey, Denver, COSearch for more papers by this author, and Michael MillerCimarex Energy Company, Tulsa, OKSearch for more papers by this authorhttps://doi.org/10.1190/urtec2013-208 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract URTeC 1581355 A uniaxial confinement clamp was used on Woodford Shale cores in hydrous pyrolysis experiments to study fracture development during thermal maturation. The clamp simulates overburden in that it prevents cores from expanding perpendicular to bedding fabric during the volume-increasing reactions associated with petroleum generation. Cores were cut from a slab of immature Woodford Shale and subjected to hydrous pyrolysis under confinement at 300, 330, and 365 °C for 72 hours to induce thermal maturities ranging from early bitumen to maximum expelled-oil generation. Two additional cores were used as experimental controls: (1) a confined core was saturated with water by heating it to 100 °C under hydrous pyrolysis conditions for 72 hours to use for characterization of the original rock, and (2) an unconfined core was heated at 365 °C for 72 hours to evaluate the effects of confinement on petroleum generation and expulsion. X-ray computed tomography (X-CT) imaging and other analyses identified five distinct beds within the cored interval. Using a tentative classification system, beds 1, 2, and 3 are described as dolomitic marlstone (DM) with total organic carbon (TOC) contents of 7.7, 5.8, and 7.7 wt. %, respectively; bed 4 is a cherty quartzose claystone (CQC) with TOC content of 5.5 wt. %; and bed 5 is a quartzose claystone with TOC content of 10.9 wt. %. Bed samples all had similar Rock-Eval hydrogen indices (600 ± 46 mg S2/g-TOC) and Tmax values (433 ± 2 °C), demonstrating organic matter uniformity and low thermal maturity. The X-CT scan of the core heated to 100 °C showed preexisting fractures that were nearly perpendicular to the bedding fabric primarily in the low-TOC DM bed 2 and CQC bed 4. Heating led to enhancement of preexisting fractures in the confined cores with the greatest enhancement occurring in CQC bed 4. The fractures increased in size and intensity with temperature. This is attributed to the internal pressure generated by volume-increasing reactions during the conversion of kerogen to bitumen and bitumen to oil and gas. The unconfined core heated to 365 °C showed no enhanced fracturing and its X-CT-scan resembled that of the 100 °C confined core. Comparison of the oil and gas yields from the confined and unconfined cores heated to 365 °C showed no significant differences, indicating that product expulsion is not inhibited by the procedure used in this study. These results also indicate that fracturing during thermal maturation is driven primarily by the enhancement of existing fractures. Keywords: fractures, rock physics, sources, unconventionalPermalink: https://doi.org/10.1190/urtec2013-208FiguresReferencesRelatedDetailsCited ByMultimodal Visualization of Vaca Muerta Shale Fabric Before and After Maturation14 May 2021 | Energy & Fuels, Vol. 35, No. 11Complex electrical conductivity changes associated with hydrous pyrolysis maturation of the Woodford ShaleWilliam F. Woodruff, Michael D. Lewan, André Revil, and Carlos Torres-Verdín16 February 2017 | GEOPHYSICS, Vol. 82, No. 2Hydrous Pyrolysis13 May 2017Organic geochemical applications to the exploration for source-rock reservoirs – A reviewJournal of Unconventional Oil and Gas Resources, Vol. 13Changes in Porosity and Organic Matter Phase Distribution Monitored by NMR Relaxometry Following Hydrous Pyrolysis Under Uniaxial ConfinementKathryn E. Washburn, Justin E. Birdwell, Michael D. Lewan, and Michael Miller26 September 2013 Unconventional Resources Technology Conference, Denver, Colorado, 12-14 August 2013ISSN (online):2159-6832Copyright: 2013 Pages: 1229 publication data© 2013 Published in electronic format with permission by the Society of Exploration Geophysicists, American Association of Petroleum Geologists, and Society of Petroleum EngineersPublisher:Unconventional Resources Technology ConferenceSociety of Exploration Geophysicists HistoryPublished: 26 Sep 2013 CITATION INFORMATION Justin E. Birdwell, Michael D. Lewan, and Michael Miller, (2013), "Geochemical Changes and Fracture Development in Woodford Shale Cores Following Hydrous Pyrolysis under Uniaxial Confinement," SEG Global Meeting Abstracts : 2012-2019. https://doi.org/10.1190/urtec2013-208 Plain-Language Summary Keywordsfracturesrock physicssourcesunconventionalPDF DownloadLoading ...