Micro-Pore Structure Characteristics and Classification Evaluation of Tight Reservoirs in Chang 6 Member of Wuqi Area

Pore structure determines the reservoir capacity and permeability, which is the key content of unconventional oil and gas exploration and development research. In this study, a series of analysis methods, such as casting thin sections, scanning electron microscope, X-ray diffraction and high-pressure mercury injection, are used to study the petrological characteristics, physical characteristics and micro-pore structure of the Chang 6 reservoir in the Wuqi area. Based on a clear comprehension of the reservoir characteristics and pore structure attributes, appropriate pore structure classification criteria tailored to the target intervals within the study area is established. The results show that the Chang-6 member in the Wuqi area is a typical low porosity, ultra-low permeability reservoir. The lithology is mainly feldspar and sandstone, the pores being mainly residual intergranular pores, with a certain amount of secondary dissolved pores, which mainly develop necking, flaky and curved throats. According to the parameters of high-pressure mercury injection, the pore structure of the reservoir can be divided into three categories: I, II and III. Among them, Type I is the best pore structure of Chang 6 reservoir in the Wuqi area, and it is a favorable exploration target in this study.