Sub- and supercritical water conversion of organic-rich shale with low-maturity for oil and gas generation: using Chang 7 shale as an example

Abstract

Organic-rich shale resources are of large reserves and high hydrocarbon generation potential but difficult to be exploited due to its high solid kerogen content. Supercritical water conversion was proposed as...

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

“…This was because the increase in temperature promoted the free radical reaction for gas production. Our previous work reported that the optimal oil and gas yield of shale in SCW at the temperature range of 300–650 °C was respectively 0.35 g/gTOC at 380 °C and 0.59 g/gTOC at 650 °C . In comparison, the oil yield from kerogen was much lower than that from shale, but the gas yield was basically the same.…”

“…Our previous work reported that the optimal oil and gas yield of shale in SCW at the temperature range of 300−650 °C was respectively 0.35 g/gTOC at 380 °C and 0.59 g/gTOC at 650 °C. 40 In comparison, the oil yield from kerogen was much lower than that from shale, but the gas yield was basically the same. In this work, as the reaction temperature increased, SCW shifted from promoting the ionic reactions (around the critical point) to promoting free radical reactions.…”

“…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 .…”

“…It is worth noting that organic matter (mainly kerogen) is distributed on the matrix skeleton of inorganic minerals. The yield and distribution of generated oil and gas are affected by inorganic minerals. − , Chang used stepwise acid treatment to remove minerals and found that carbonates promote the generation of hydrocarbon, while silicates suppress shale oil production. Hu found that, for kerogen pyrolysis at 520 °C in an atmosphere of N 2 , montmorillonite and gypsum are strong catalysts, while calcite is an inhibitor.…”

“…Hu 48 found that, for kerogen pyrolysis at 520 °C in an atmosphere of N 2 , montmorillonite and gypsum are strong catalysts, while calcite is an inhibitor. Zhao 40 found the minerals of Chang 7 shale increased the oil yield by 34.2% at 380 °C as a whole but had a negligible effect on gas generation. Chen et al 49 discovered that kaolinite in shale disappears when the temperature exceeds 500 °C, which could be due to dihydroxylation of kaolinite into amorphous meta kaolinite.…”