The Characteristics And Influence Of Shale Adsorption Of Wufeng-longmaxi Formation Shale In Southern Sichuan Basin

With the exploration of shale gas,people have realized that the study of shale gas bearing property is of great significance for the further exploration of shale gas.In this dissertation,the marine shale in southern Sichuan was selected to explore the mechanism of shale gas adsorption by using organic geochemical experiments,gas adsorption and methane adsorption experiments,then the change of shale gas bearing property was analyzed.The results showed that the SDR model fits the methane adsorption experiment with the best effect and can be used to characterize the shale adsorption capacity in the study area.The source rock conditions in study area are excellent,and the total organic carbon content is significantly positively related to the adsorption capacity of the shale.Organic matter and clay minerals exist adsorption competition,and the organic matter content dominates in the adsorption competition.Type III kerogen has the strongest adsorption capacity among organic matter types.However,the study area is basically in the over mature stage,and organic matter types have little effect on adsorption capacity.The maturity of shale organic matter is negatively correlated with the shale gas bearing property,because in the over mature stage,the asphalt and petroleum filled space of the organic pores and reduce pore connectivity.The pore structure of shale is complex,a large number of micropores contribute to the pore volume and pore specific surface area,providing more adsorption spaces for shale gas and increasing the adsorption capacity of shale.Temperature and pressure also have a significant effect on adsorption capacity,temperature is negatively correlated with adsorption capacity,and pressure is the opposite.As the burial depth increases,the total gas content of the shale increases rapidly and then stabilizes,the absorbed gas content increases rapidly and then decreases and has the same proportion as free gas at a certain depth.This depth will vary with changes in organic matter abundance and shale porosity.