Pore Type, Pore Structure, and Controlling Factors in the Late Triassic Lacustrine Yanchang Shale, Ordos Basin, China

Organic-rich lacustrine shales in the Upper Triassic Yanchang Formation with thermal maturity mainly oil window are main shale and gas system strata of Ordos Basin, China. Pore systems important for storage transfer gas. The objectives this study to identify pore types structures investigate controlling factors types, structures, total porosities Shale. In study, organic-rich mudstones, mudstones siltstone interlayers, siltstone, sandstones were selected from 15 wells southern Basin. X-ray diffraction, pyrolysis, scanning electron microscopy (SEM), low-pressure nitrogen adsorption analysis, helium porosimetry conducted mineral compositions, porosities, factors. Siltstone sandstone interlayers heterogeneously developed petrology, composition, geochemistry, type, structure, porosity different those mudstones. usually have more quartz feldspars, greater detrital grain sizes, relatively better sorting but lower clay minerals, organic carbon (TOC), amount free liquid hydrocarbons values (S1), residual (S2), compared Interparticle (interP), intraparticle (intraP) pores, pores (OPs) both siltstones OPs observed samples (e.g., 0.5–0.85%). inorganic size is than that OPs. Additionally, diameters also generally higher volumes (PVs) sizes less 10 nm, between 50 nm (PV, 10–50 nm), specific surface area (SSA), they PVs PV, when interlayers. dominant type TOC (first order), sources OM (second (third while abundances rigid grains SSA PV. Both abundant distribution (PSD), related abundance carbonate cement content. PV Shale reservoirs may increased