Characteristics and influencing factors of desorption gas in Wufeng-Longmaxi formations in Fuling area, Sichuan Basin

Adsorption gas is the main form of shale gas, and research of the characteristics and influencing factors of desorption gas can guide the exploration and development of shale gas. The variation of desorption rate, the change of desorption gas volume and the difference of carbon isotopes were analyzed using desorption experiments of shale gas from Wufeng-Longmaxi formations in Fuling area in Sichuan Basin. The amount of natural gas desorbed within a certain time after a core is loaded into the desorber is measured and mainly reflects the amount of adsorbed gas and part of the free gas in the rock. The comparison with shale quality shows that the amount of desorbed gas is positively correlated with total organic carbon content, brittle mineral content, and the illite/smectite ratio in clay, but not related to illite content. It has a negative correlation with chlorite content. The amount of desorbed gas has a positive correlation with the micropore volume and possesses a good positive correlation with the mesopore volume, but not with the macropore volume.