Using Structural Diagenesis to Infer the Timing of Natural Fractures in the Marcellus Shale

Abstract

PreviousNext No AccessUnconventional Resources Technology Conference, Denver, Colorado, 12-14 August 2013Using Structural Diagenesis to Infer the Timing of Natural Fractures in the Marcellus ShaleAuthors: Laura PommerJulia F. W. GalePeter EichhublAndrás FallStephen E. LaubachLaura PommerBureau of Economic Geology, University of Texas at AustinSearch for more papers by this author, Julia F. W. GaleBureau of Economic Geology, University of Texas at AustinSearch for more papers by this author, Peter EichhublBureau of Economic Geology, University of Texas at AustinSearch for more papers by this author, András FallBureau of Economic Geology, University of Texas at AustinSearch for more papers by this author, and Stephen E. LaubachBureau of Economic Geology, University of Texas at AustinSearch for more papers by this authorhttps://doi.org/10.1190/urtec2013-167 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract URTeC 1580135 Economic production of oil and gas from mudrocks such as the Devonian Marcellus Shale relies on hydraulic fracture stimulation. The orientation, size, porosity, and strength of subsurface natural fracture systems can influence the growth of hydraulic fractures by conducting fluid, opening, or slipping during treatment. Knowledge of the orientation, size, porosity, and other attributes of natural fractures in the Marcellus Shale is based on core and outcrop data. Fractures in outcrop and core may not be the same age, however, and uncertainty in knowledge of fracture timing and origin impedes use of outcrop data for subsurface applications. Previous studies of fracture timing correlated fracture strikes in outcrop with inferred paleostress directions from past tectonic events. Fractures in the subsurface typically share common orientations with those observed in outcrop, but most fractures in outcrop are barren joints, whereas most of those in the subsurface are lined or sealed with cement. We compare rare fracture cements in outcrop with subsurface examples to test the hypothesis that some fractures in outcrops are equivalent to subsurface fracture systems. We compare fracture cement morphology, texture, mineralogy, and geochemistry from a suite of outcrop samples from Union Springs, New York, with fractures in four cores from a currently producing reservoir in southwest Pennsylvania. Light-microscope petrography and cold cathodoluminescence of calcite in outcrop and some core samples reveal crack-seal and blocky textures that record fracture opening and sealing. Other core samples have fibrous calcite fill and other mineral phases. Using aqueous and hydrocarbon fluid inclusions from synkinematic fracture cements, we can tie fracture growth to burial history. Stable isotopes in calcite fracture cements from different fracture types in cores and outcrop range from -21.5‰ to +4.4‰ δ13C PDB and -8.0‰ to -12.0‰ δ18O PDB. Assuming burial history predicts thermal history, isotopic composition together with fluid inclusions suggest calcite formed at 50-100°C, and that fracture timing was Acadian or early Alleghanian, forming during burial. The outcrop fractures tested in this study appear analogous to subsurface fractures, although other fracture types are present in the cores that are not observed in outcrop; additionally, the orientations in outcrops and the subsurface do not always match. Keywords: gas, production, porosity, correlation, fractures, fluid, modelingPermalink: https://doi.org/10.1190/urtec2013-167FiguresReferencesRelatedDetailsCited ByCharacteristics and Main Controls of Tectonic Fractures and Their Contribution to Deep Tight Reservoirs: A Case Study of the Huoshiling-Shahezi Formations in Gudian Half-Graben, Songliao Basin, China8 August 2022 | Lithosphere, Vol. 2022, No. Special 12Mudrock Components and the Genesis of Bulk Rock Properties1 October 2019Computational modelling of multi-stage hydraulic fractures under stress shadowing and intersecting with pre-existing natural fractures17 December 2018 | Acta Mechanica, Vol. 230, No. 3Two-Scale Geomechanics of Shale25 June 2018 | SPE Reservoir Evaluation & Engineering, Vol. 22, No. 01An application of outcrop analogues to understanding the origin and abundance of natural fractures in the Woodford ShaleJournal of Petroleum Science and Engineering, Vol. 164Guidelines for the Handling of Natural Fractures and Faults in Hydraulically Stimulated Resource Plays20 October 2015Marcellus fracture characterization using P-wave azimuthal velocity attributes: Comparison with production and outcrop dataTanya L. 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Laubach, (2013), "Using Structural Diagenesis to Infer the Timing of Natural Fractures in the Marcellus Shale," SEG Global Meeting Abstracts : 1639-1644. https://doi.org/10.1190/urtec2013-167 Plain-Language Summary KeywordsgasproductionporositycorrelationfracturesfluidmodelingPDF DownloadLoading ...