Shale gas desorption behavior and carbon isotopic variations of gases from canister desorption of two sets of gas shales in south China

Abstract Four shale samples from the Lower Silurian Longmaxi Formation and the Lower Cambrian Shuijingtuo Formation in the eastern part of Chongqing, SW China, were subjected to canister desorption experiments at reservoir and elevated temperatures (up to 90 °C) to investigate shale gas release behaviors and their variations in chemical and isotopic compositions of desorbed gases. Both the ratios of gas released at reservoir temperature to the total desorbed gas at reservoir and elevated temperatures and the desorption rates suggest that the Longmaxi shale gas is more easily released than the Shuijingtuo shale gas. Scanning electron microscope (SEM) observation, along with low temperature CO2 and N2 adsorption results, suggests that organic matter hosted pores with diameters of 2–100 nm are rich in the Longmaxi shales, whereas well-developed micropores (