Pore structure analysis of tight reservoirs in He-8 Member of Upper Paleozoic in the southwestern Ordos Basin, China

Abstract

Quantitative characterization of the pore structure in tight reservoir can provide basic parameters for the evaluation of the reservoir quality. By using the cast thin-section petrography, scanning electron microscopy, mercury injection capillary pressure, and constant-rate mercury injection, we have evaluated the distribution characteristics of pore throat and its contribution to permeability. In addition, we have established the relationship between different pore-throat structure parameters and reservoir physical, which provides theoretical support for reservoir evaluation of the He-8 Member in the study area. The results indicate that the pore structure exerts a great control on the quality of the reservoir. Large pore throats (>0.15 μm) are the main contributors to the high seepage capacity of the reservoir. Throat radius, throat distribution, and pore-throat ratio are the key factors controlling the quality of tight reservoir. The He-8 Member of the Upper Paleozoic in the study area is dominated by tight reservoirs, accompanied by a small number of conventional reservoirs.

Densification Mechanisms and Pore Evolution Analysis of a Tight Reservoir: A Case Study of Shan-1 Member of Upper Paleozoic Shanxi Formation in SW Ordos Basin, China

“…The present-day structure exhibits a large monocline feature, with higher elevations in the east and south and lower elevations in the west and north. The Upper Paleozoic succession comprises the Carboniferous Benxi Formation, Permian Taiyuan Formation, Shanxi Formation, Shihezi Formation, and Shiqianfeng Formation [2]. These formations represent a transitional sequence of continental to marine clastic rock deposits.…”

“…Oil and gas exploration practices have demonstrated that tight sandstone gas reservoirs are crucial targets for natural gas exploration [1][2][3]. The Shan-1 Member of the Permian Shanxi Formation in the Southwest (SW) Ordos Basin represents a tight reservoir.…”

“…The distribution of gas in tight reservoirs is constrained, posing a significant challenge to oil and gas exploration and development. Understanding pore evolution and densification, which are focal points in the study of reservoir characteristics [2], is essential.…”