Reservoir Characteristics and Controlling Factors of the Benxi Formation in the Eastern Yanchuan Block

Abstract

With the continuous advancement of oil and gas exploration in China, the recoverable reserves of conventional oil and gas fields have entered a stage of high depletion, and unconventional oil and gas resources have gradually become important targets for exploration and development. Among them, tight sandstone gas has attracted considerable attention due to its large resource potential [1,2]. However, compared with conventional reservoirs, tight sandstone reservoirs are generally characterized by low porosity and permeability, narrow pore-throat systems, dense lithology, and complex diagenetic processes, which increase the difficulty of reservoir evaluation and productivity prediction. The Benxi Formation in the eastern Yanchuan Block of the Ordos Basin mainly develops tight sandstone reservoirs and represents an important gas-bearing interval in the Upper Paleozoic. In this study, the tight sandstone reservoirs of the Benxi Formation in the eastern Yanchuan Block of the Ordos Basin were selected as the research object. Based on previous studies, core observation and casting thin-section analysis were conducted to investigate the petrological characteristics, pore types, and diagenetic features of the reservoirs, as well as their influence on reservoir physical properties. The results indicate that multiple pore types are developed in the tight sandstone reservoirs of the Benxi Formation, with complex pore structures. Reservoir quality is mainly controlled by sedimentation and diagenesis. This study clarifies the evolutionary characteristics of tight sandstone reservoirs in the Benxi Formation and provides a theoretical basis for predicting favorable tight gas“sweet spots”in the study area.