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TitleThe influence of rigid matrix minerals on organic porosity and pore size in shale reservoirs: Upper Devonian Duvernay Formation, Alberta, Canada
AuthorKnapp, L J; Ardakani, O HORCID logo; Uchida, S; Nanjo, T; Otomo, C; Hattori, T
SourceInternational Journal of Coal Geology vol. 227, 103525, 2020 p. 1-23,
Alt SeriesNatural Resources Canada, Contribution Series 20190532
Mediapaper; on-line; digital
File formatpdf
NTS72M; 73D; 73E; 73L; 73M; 74D; 82M; 82N; 82O; 82P; 83; 84A; 84B; 84C; 84D; 93A; 93H; 93I; 93P; 94A
Lat/Long WENS-120.0778 -110.0514 57.0000 51.0000
Subjectsfossil fuels; sedimentology; mineralogy; Science and Technology; Nature and Environment; Upper Devonian; petroleum resources; hydrocarbons; reservoir rocks; porosity; pore size; thermal maturation; Duvernay Formation; Phanerozoic; Paleozoic; Devonian
Illustrationslocation maps; stratigraphic columns; tables; charts; graphs
ProgramGeoscience for New Energy Supply (GNES) Shale Reservoir Characterization
Released2020 05 28
AbstractOrganic porosity is an important component of the pore system in many shale hydrocarbon reservoirs. While much research has been directed towards understanding the development of organic porosity as a function of thermal maturity, relationships between mineralogy and organic porosity have been less extensively investigated. This study illustrates the role of rigid matrix minerals, particularly biogenically-sourced microcrystalline quartz, on organic porosity and pore size enhancement. The Upper Devonian Duvernay Formation of western Canada is a siliceous-calcareous self-sourced reservoir with 3.2-3.49 wt.% average total organic carbon (TOC) in a study area occurring in the volatile oil to dry gas thermal maturity zones. Biogenic silica is widely distributed throughout the matrix as microcrystalline quartz and locally comprises >50 wt.% of the rock. Porosity and pore size data gathered from BIB- and FIB-SEM, helium porosimetry, H1 NMR T2, and MICP indicate that organic porosity and pore size is enhanced when in association with biogenic silica. Biogenic silica forms a rigid siliceous matrix framework that limits compaction of pores and ductile organic matter and clay minerals. Where biogenic silica concentration is low, clay mineral (mica+illite) interparticle micro- and fine mesopores dominate. In these samples detrital quartz and biogenic silica have limited influence on pore size other than to preserve the small fraction of organic macropores. The occurrence of biogenic- and clay-dominated pore systems varies systematically with stratigraphic and lateral variations in lithofacies, and sharp contrasts are observed across sequence boundaries. The observation that mineralogy strongly influences the ability for organic pores to be preserved confirms that studies examining the relationship between thermal maturity and organic porosity must account for mineralogical variations.
Summary(Plain Language Summary, not published)
This study discuss the mechanisms by which rigid matrix minerals, in this case microcrystalline quartz sourced from biogenic silica, exert a strong control on pore volume and pore size distribution, particularly for organic porosity.

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