In this study, the hydrocarbon generation of 1–4 cm sized shale in supercritical water (SCW) was investigated. The results showed that temperature was the most important factor affecting the hydrocarbon generation of organic-rich shale in the presence of supercritical water. In the temperature range of 380–450 °C, the optimum oil generation temperature was 430 °C. The produced oil component became heavier with increasing temperature. Increasing temperature was beneficial to gas production and improved the selectivity of H2 and CH4. In the pressure range of 22.5–27.5 MPa, oil and gas production decreased with increasing pressure. The influence of pressure on conversion path was almost negligible. Pressure affected the hydrocarbon generation of shale in supercritical water by affecting hydrocarbon expulsion. In the water-shale mass ratio range of 0.5–5 and the reaction time range of 1–12 h, increasing both parameter ranges was conducive to the hydrocarbon generation of oil shale. The selectivity of H2 increased and that of CH4 and CO2 decreased with increasing water-shale mass ratio. The selectivity of CH4 and C2H6 increased with increasing reaction time.
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