Study on the influence of the water-shale mass ratio on organic carbon migration and pore evolution during hydrocarbon generation by pyrolysis of medium-and low-maturity organic-rich shale in supercritical water conversion

Oil reservoirs contain significant amounts of water. Therefore, the role of water in the in situ hydrocarbon generation of medium-and low-maturity organic-rich shale cannot be ignored. In this study, a self-developed reaction system was used to simulate hydrocarbon generation under supercritical water in situ conversion, examining the influence of water-shale mass ratio changes on organic carbon migration and pore evolution. The results showed that higher water-shale mass ratios were conducive to the conversion of organic carbon in shale and the migration of organic carbon to gas-phase products. As the water-shale mass ratio increased, the proportion of carbon elements in carbon dioxide from organic sources gradually decreased, while that of carbon elements from inorganic sources gradually increased. Increasing the water-shale mass ratio from 0.5 to 5, the porosity and permeability of shale were greatly improved, with porosity increasing more than threefold and permeability more than fivefold.