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

Abstract

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 °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 °C, the oil production rate reached a maximum of 4.2 kg oil•t −1 shale at 430 °C, and the gas production rate reached a maximum of 36.02 m 3 gas•t −1 shale at 450 °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 °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 °C was only due to the development of microfractures.

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

“…In recent years, supercritical water (SCW) has been shown to be superior in terms of conversion efficiency in biomass conversion, − solid waste treatment, − and utilization of coal and heavy oil. − The conversion of low-maturity shale into hydrocarbon resources with SCW has also received extensive attention. − SCW refers to water with the temperature and pressure both exceeding the critical point (374.3 °C, 22.1 MPa), − and it has excellent physicochemical properties such as high solubility, high reactivity, and high diffusivity. The literature − reported that hydrocarbon generation efficiency in SCW was significantly higher than that in N 2 , steam, and subcritical water, and the yield as well as the composition of oil and gas were mainly dependent on temperature. In terms of converting oil shale, the comparisons between SCW and other mediums are shown in Table .…”

Reaction Kinetics Study on Hydrocarbon Generation of Medium- and Low-Maturity Organic-Rich Shale in Supercritical Water

“…In recent years, the technology of hydrocarbon generation from medium- and low-maturity organic-rich shale in supercritical water conversion has been given much attention. − The thermal degradation of medium- and low-maturity organic-rich shale to produce hydrocarbon is a complex physicochemical process, − which results in a wide variety of products, which makes it difficult to determine the kinetic law and mechanism of pyrolysis. In addition, supercritical water was introduced into the transformation of medium- and low-maturity organic-rich shale to generate hydrocarbons, which undoubtedly made the pyrolysis process more complicated.…”