Methane Adsorption and Desorption on Continental Shaly Matrix: Implications for Shale Gas Condensate Exploration and Production

Shale gas condensate is a burgeoning unconventional resource with adsorbed methane (CH4) as its dominant component. Successful evaluation of marine shale gas gives limited insights into the evaluation of continental shale gas condensate due to their different occurrence patterns of organic matter and inorganic minerals and resultant contributions to pore development and CH4 ad-/desorption capability. To address this issue, we employed an advanced low-temperature oxygen plasma (LTOP) technology to extract organic matter from the continental shaly matrix. Results showed that the continental shaly matrix contains more clay minerals and less quartz, and develops fewer pores and fractures than typical marine shaly matrix. The organic matter-hosted pores instead of inorganic mineral-hosted pores are more weighted to the pore development in the continental shaly matrix. However, the inorganic minerals of the continental shaly matrix contribute more to CH4 adsorption capability than the organic matter, which could be attributed to the higher density of available adsorption sites toward CH4. Besides, the CH4 ad-/desorption hysteresis is more pronounced for the organic matter-free continental shaly matrix than the raw continental shaly matrix, which is attributed to the remarkable CH4 adsorption-induced clay mineral swelling. Overall, the effects of inorganic minerals in CH4 adsorption and desorption, particularly clay minerals, are crucial for continental shale gas condensate exploration and production.