Development characteristics and formation stages of tectonic fractures of Cretaceous Bashijiqike tight sandstone reservoir in Keshen gas field, Tarim Basin, China

Abstract

The Cretaceous Bashijiqike formation in the Kuqa Depression of the Tarim Basin is ultra-low porosity and ultra-low permeability reservoir, where fractures have important influences on single well productivity and natural gas accumulation. According to the core CT scanning, casting thin section, laser copolymerization, imaging logging and other data, the basic development characteristics of fracture in this area are analyzed. Based on the analysis results of the core fracture cutting relationship, the carbon and oxygen isotope of the fractures filling, and the temperature measurement of the inclusions, the main stages of the regional fractures are determined. The results show that the fractures in the study area are mainly high angles, mostly filled with calcite and gypsum, and the fracture width is generally less than 0.2mm. There are three groups of structural fractures, which are EW/NE-SW and NW-SE, with the dominant orientations being NE-SW and NW-SE. The structural fracture were formed in three stages, which were the late Yanshan movement period-early Himalayan tectonic movement, the middle period of Himalayan, and the late period of Himalayan tectonic movement. The tectonic activity of the late Himalayan tectonic movement is the strongest, and the formation of fractures formed in this period were low degree of filling and effective.