Geological controls on the methane storage capacity in organic-rich shales

Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin, China

Sorption capacities and pore characteristics of bulk shales and isolated kerogens have been determined for immature, oil-window, and gas-window mature samples from the Lower Toarcian Posidonia shale formation. Dubinin–Radushkevich (DR) micropore volumes, sorption pore volumes, and surface areas of shales and kerogens were determined from CO2 adsorption isotherms at −78 and 0 °C, and from N2 adsorption isotherms at −196 °C. Mercury injection capillary pressure porosimetry, grain density measurements, and helium pycnometry were used to determine shale and kerogen densities and total pore volumes. Total porosities decrease through the oil-window and then increase into the gas-window. High-pressure methane isotherms up to 14 MPa were determined at 45, 65, and 85 °C on dry shale and at 45 and 65 °C on kerogen. Methane excess uptakes at 65 °C and 11.5 MPa were in the range 0.056–0.110 mmol g–1 (40–78 scf t–1) for dry Posidonia shales and 0.36–0.70 mmol g–1 (253–499 scf t–1) for the corresponding dry kerogens. A...

/pdf/high-pressure-methane-adsorption-and-characterization-of-4guj85cxwl.pdf

High-pressure methane adsorption and characterization of pores in Posidonia shales and isolated kerogens.

Pore types, pore size, and pore abundance vary systematically across thermal maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM). Destruction of primary pores during early burial (to ∼0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM “stringers.” Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3–4 nm [0.00000012–0.00000015 in.]). At low maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. At higher maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-maturity ( ∼1.2%–1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low maturity. A large portion of OM within high-maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred. Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).

Pore types and pore-size distributions across thermal maturity, Eagle Ford Formation, southern Texas

Shale gas potential of the major marine shale formations in the Upper Yangtze Platform, South China, Part II: Methane sorption capacity

Experimental investigation of main controls to methane adsorption in clay-rich rocks

Lithofacies and reservoir characteristics of saline lacustrine fine-grained sedimentary rocks in the northern Dongpu Sag, Bohai Bay Basin: Implications for shale oil exploration

Junli Qu

Papers

Experimental investigation of main controls to methane adsorption in clay-rich rocks

Lithofacies and reservoir characteristics of saline lacustrine fine-grained sedimentary rocks in the northern Dongpu Sag, Bohai Bay Basin: Implications for shale oil exploration