Experimental Study on Hydrocarbon Generation Characteristics of Type II Kerogen from Low-Maturity Shale in Supercritical Water

Supercritical water conversion of low-maturity shale is a promising method to produce oil and gas. Hydrocarbon generation from kerogen is influenced by inorganic minerals in shale. This study aims to clarify hydrocarbon generation characteristics of pure kerogen in supercritical water by removing inorganic minerals by acid-pickling. A series of experiments on hydrocarbon generation of kerogen in the temperature range of 300–700 °C were carried out in a batch reactor, and the produced oil and gas were quantitatively analyzed. The results showed that when the temperature increased, the oil yield had experienced a variation of first an increase and then a decrease with a peak value of 0.19 g/gTOC at 380 °C, while the gas yield continued to increase to 0.88 g/gTOC at 700 °C. By increasing the temperature from 300 to 500 °C, it would favor producing high quality oil with more light distillates (70% at 500 °C) and less asphaltene (5% at 500 °C). The main gas products were methane, hydrogen, and carbon dioxide as well as C2+ hydrocarbons. The proportion of hydrogen increased with temperature (30% at 700 °C), while the proportion of methane peaked to 51% at 600 °C. Elevated temperatures in a supercritical water atmosphere increase ring-opening processes and the cleavage of branched side chains, boosting the maturation of the kerogen.