Gas-bearing Ability Evaluation Of The Lower Paleozoic Shale In Southeast Chongqing

Southeast Chongqing is located in the wide spaced anticlines in East Szechwan and wide spaced synclines in West Hubei and East Chongqing, there developed two sets of shale with high organic matter abundance and high thermal evolution degree, which distributed widely and the gas content changes largely, which have a great potential.The organic matter types in Niutitang Formation of the early Cambrian Series, Southeast Chongqing, are mainly Type I and II. The organic matter type in Wufeng formation black shale of upper Ordovician and Longmaxi lower silurian shale is ?-?1.The brittle minerals'contents in Niutitang Formation of the early Cambrian Series, Southeast Chongqing are as follows, quartz 18%-84%, carbonate 1%-76%, clay mineral 3%-31%.Pore constitution of Niutitang Formation is the organic matter 2%-8%, clay floor 7%-12%, and brittle mineral 81%-91%. Pore throat diameter changes from 20-50nm. The brittle minerals' contents in Wufeng formation of upper Ordovician and Longmaxi Formation of lower Silurian are as follows, quartz 23.8%-81%, carbonate 1.1%-19%, clay mineral 12%-65.7%. Pore constitution of the two formations is the organic matter 5%-11%, clay floor 28%-65%, brittle mineral 31%-52%. Pore throat diameter changes from 20-50nm.The main controlling factors of gas content in shale are the geochemical index, mineral composition, property index and the external factors such as depth, temperature, humidity conditions and pressure. The organic matter type and maturity, brittle mineral content, clay mineral content, porosity and the pore porosity features are the main factors of shale gas accumulation, and the external conditions such as depth, temperature and pressure effect shale gas accumulation in a certain degree.The favorable development areas of shale gas for those two formations are predicted base on the integration of America mainly shale basin accumulation character and southeast ChongQing gas-bearing shale geology feature and the main influence facter of the shale gas content.According to the isothermal adsorption experiment, site desorption test, logging interpretation results and other methods, YouYang country and XiuShan country in Chongqing are the favorable areas of Niutitang Formation, the lower part of the black shale on vertical belong to the favorable layer section and the gas content is range from 2m3/t-12m3/t. LianHu country of PengShui county and QianJiang distict in Chongqing are the favorable areas of Longmaxi Formation, the gas content is over 2m3/t.