Types, Evolution of Fractures, and Their Relationship with Oil and Gas Migration of Permian Changxing Formation in Yuanba Gas Field of Sichuan Basin, China

Abstract

Yuanba gas field of Sichuan Basin is characterized by weak-tectonic deformation, and the fractures have had a significant effect on oil and gas migration. This paper investigates the types, evolution of fractures, and their relationship with oil and gas migration of the Permian Changxing Formation of the Yuanba gas field according to geological and geochemical analyses. Four genetic types of fractures with different occurrences were distinguished: intercrystal fractures, pressure solution fractures (stylolites), structural fractures, and overpressure fractures. Intercrystal fractures present multiple straight edges between the dolomite particles and no fixed direction. Pressure solution fractures are in the form of zigzags. Structural fractures have straight edges and a certain direction and are usually distributed in groups. Overpressure fractures have irregular shapes and irregular directions and occur in multiple quantity. According to the comprehensive analyses, the intercrystal fractures, pressure so...