How argillaceous reservoirs exhibit better quality than silty mudstones? Anomalous behavior of shale gas-bearing properties of continental fine-grained sediments in Southwest China and its possible forcing mechanisms

• DOI: 10.1016/j.petsci.2021.09.032
• Publication Date: 2021-09-21T15:29:23Z
• Authors: Wei Yang; Liang Xu; Dong-Xia Chen; Zhen-Xue Jiang; Zi-Ya Zhang; Bin Hao; Ru-Si Zuo; Qian-You Wang; Rong Chen
• Keywords: Bedding; Terrigenous sediment; Petrophysics; Tight oil

Achieving a thorough understanding of how primary sedimentary granularity drives considerable heterogeneity in internal reservoir attributes terrigenous fine-grained deposits is great significance. We investigated the quantitative differentiation and its corresponding driving forces physical properties pore-structure characteristics silty-mud sediments Upper Triassic Xujiahe Formation (SW China) using multi-method approach. The results show that micro-mesopore volume surface area mudstones/shales are apparently higher than those silty mudstones remarkable threefold rise average permeability also presents. Extensively distributed bitumen pores occurring mostly along brittle mineral grains or forming clay-organic complexes make contributions to shrinking microcracks. Furthermore, an evidently concentration clay minerals mudstone/shale reservoirs primarily responsible for development two types inter-crystalline grain aggregates between well-oriented platelets. These major causes facilitate formation micro-bedding fractures/non-bedding microfractures connected fracture pore-fracture networks, high-quality argillaceous by strongly enhancing storage spaces seepage capacities. Finally, conceptual model established interpreting differential reservoir-forming mechanism two-sided effects on petrophysical quality continental sediments.