An approach to the geology of the shale gas in the Lower Permian Kalagang Formation, Jimunai depression, northern Xinjiang

The geological characteristics of the shale gas in the Lower Permian Kalagang Formation, Jimunai depression, northern Xinjiang are approached on the basis of organic geochemical signatures and reservoir characteristics. The dark shales from the lower member of the Lower Permian Kalagang Formation consist mainly of carbonaceous shales with the total organic carbon contents ranging between 0.3% and 4.32%, indicating a moderate organic carbon abundance and type III of organic matter types. Ro values ranging between 1.43% and 2.87% suggest the mature to overmature stages of thermal evolution of kerogens with good hydrocarbon potential. The mineral compositions include quartz, feldspar and clay minerals. The pore types are composed of macropores, mesopores and micropores. The reservoir spaces are represented by intragranular and intergranular solution openings. The porosity values vary from 0.97% to 1.52%, and the permeability values from 0.0097 to 0.0197mD with an average of 0.0139mD, implying that the black shales in the study area have good reservoir potential.