Experimental study of the impact on methane adsorption capacity of continental shales with thermal evolution

Abstract In order to reveal the methane adsorption capacity influenced by the geological factors in the process of thermal evolution, a shale sample from Chang-7 Member of the Yanchang Formation in the southeastern part of the Ordos Basin was collected. Seven different samples were acquired to simulate burial depths through the thermal simulation experiment. The organic geochemical parameters, mineral composition, pore structure, and methane adsorption capacities were measured. According to this research, influence factors on methane adsorption capacity considering thermal evolution can be divided into three kinds: Physical factors such as specific surface area and pore diameter, organic geochemical factors such as TOC and thermal maturity, as well as mineral composition factors such as clay minerals and andreattite. Geological factors have intricate impacts on the methane adsorption capacity. Considering each factor was combined together, it may increase the significance of the adsorption amount and influence factors. Micro-pore is the most important factor, it has a positive correlation with the methane adsorption capacity. The adsorption quantity increases when TOC decreases due to the thermal evolution of organic produced micro-pores which increases the adsorption space. In addition, the adsorption capacity of shale has a negative correlation to the burial depth. The deeper it's buried the faster the adsorption capacity decreases.