Experimental Investigation on the Organic Carbon Migration Path and Pore Evolution during Co-thermal Hydrocarbon Generation of Low Maturity Organic-Rich Shale and Supercritical Water

In this study, a non-isothermal heating reactor was used to simulate the hydrocarbon generation of 1-4 cm-sized low maturity organic-rich shale under the action of supercritical water. Under the condition of maintaining a pressure of 24 MPa, a mass ratio of water to shale 1:1, and a total reaction time of 2.5 h, the effects of different temperature conditions (380-450 degrees C) on hydrocarbon generation efficiency, organic carbon migration ratio, and pore permeability characteristics were investigated. The results showed that the oil production rate first increased and then decreased, and gas production rate continued to increase with increasing temperature. In the range of 380-450 degrees C, the oil production rate reached a maximum of 4.2 kg oil center dot t-1 shale at 430 degrees C, and the gas production rate reached a maximum of 36.02 m3 gas center dot t-1 shale at 450 degrees C. Increasing temperature would promote the increase in the relative content of heavy components in oil. The selectivity of hydrogen and methane was promoted, while carbon dioxide was inhibited by increasing temperature. The distribution proportion of organic carbon in the oil-phase products and wastewater gradually decreased, while the distribution proportion in the gas-phase products increased with the increase in temperature. The porosity, permeability, and specific surface area of shale all increased with the increase in temperature. The increase in porosity caused by increasing temperature less than 430 degrees C was attributed to the fact that increasing temperature promotes the conversion and release of organic matter and the development of microfractures. The increase in porosity by increasing temperature more than 430 degrees C was only due to the development of microfractures.