Basic Characteristics and Exploration Prospect of the Upper Triassic Xujiahe Formation Continental Shale Gas in Sichuan Basin of China

Abstract

URTeC 1619344 Very little attention were paid for the continental shale sequence compared to marine shale of the Sichuan Basin, although the continental shale owns good conditions for the shale gas accumulation. The further research of shale gas accumulation conditions is meaningful to realize the exploration and development prospects effectively, and to expand the field of exploration and development. Based on the research of the development characteristics, organic type of shale grade of maturity, abundance of organic matter, rock and ore characteristics, physical properties of reservoir, type of pore, and preservative conditions of the continental shale of the 5th sector of the Xujiahe Formation of Upper Triassic in Western Sichuan Depression, oil-bearing property and resource potential are comprehensive studied. The research shows that the thickness of shallow lake facies black mud shale in the 5th sector of the Xujiahe Formation is about 250 to 300 m, and the average of TOC is more than 2% in the mature to high mature stage. The micro-fractures, nano-micron level pores, clay mineral intergranular micro pores and slightly soluble holes are developed in shale, and the quantity of brittle minerals such as quartz, feldspar, carbonates is more than 60%. In spite of multiphase tectonic evolution, the shale’s preservation conditions of shale are excellent. The shale shows very well oil-bearing property. Natural gas was generally released while drilling, and the real quantity of shale gas of the in-situ sample ranges from 0.42 to 6.27 cubic meters per ton, with an average of 1.37 cubic meters per ton, and to absorbed gas mainly, which shows the better characteristics of gas content. The Xujiahe Formation shale has high gas resource potential and high abundance of gas resources. The quantity of the shale gas resource with depth less than 3500m is 0.01 Tcf, gas-bearing abundance is from 10.06×108 to 13.15×108 cubic meters per square kilometer. The quantity of brittle mineral of the continental shale reservoir in the Xujiahe Formation (quartz and carbonate) is high, which predicts that fracturing is easier to form network fractures, to achieve volume transformation and showing a good development prospects.