Oil Shale

Table S1: Al-normalized enrichment factors of As, Mo, Pb, and U in Lunpola oil shales (UCC reference).

In recent years, in-situ conversion has shown great potential for large-scale oil shale exploitation, but the evolution of hydrocarbon products and residues during thermal conversion remains insufficiently studied. Using oil shale samples from the Fushun, Huadian, and Meihe basins, we conducted heating experiments in a rapid open system to investigate hydrocarbon generation and residue evolution at different stages, providing theoretical support for in-situ recovery. At ≤ 300 °C, water accounts for 40.0–57.4 wt.%, oil yield is below 1 wt.%, and hydrocarbon potential remains excellent. At 400–475 °C, organic matter is greatly consumed, with TOC reduced by 7.7–9.8 wt.%, and S2 conversion reaches 96.19–97.18%. Hydrocarbon potential drops from excellent to good, marking the main oil generation and expulsion stage. At 520 °C, oil and water yields stabilize, gas yield rises slightly with dry gas as the main component, and residual potential gradually declines. Fushun oil shale is dominated by type I kerogen, whereas Huadian and Meihe oil shales are dominated by type II, with decreasing oil-generating capacity. Organic matter enters the oil window at 300 °C and peaks at 475 °C. We recommend 400–475 °C as the optimal heating range for oil shale in-situ conversion.

Two different shale oils were produced by the pyrolysis of oil shale from the Attarat Um-Ghudran and El-Lajjun areas in Jordan. The ionic liquids [BMIM]BF4 and [BMIM]PF6 were used to extract sulfur compounds from the shale oils. The two shale oils generated from Attarat and El-Lajjun were found to contain 12.1 and 11.2 wt.% sulfur, respectively. The extraction of sulfur compounds from shale oil was studied at 20, 40, and 60 °C, with 40 °C being the optimum. The volume ratios of ionic liquid to shale oil (IL/SO) investigated were 1.0:1.0, 1.0:3.0, 1.0:5.0, 1.0:8.0, and 1.0:10.0. For Attarat shale oil, the 1.0:5.0 ratio resulted in removal efficiencies of 58.7% (7.1/12.1) and 54.6% (6.6/12.1) for [BMIM]PF6 and [BMIM]BF4, respectively, which were lower than those calculated for the 1.0:1.0 (IL/SO) ratio, i.e., 62.8% (7.6/12.1) and 57.9% (7.0/12.1), respectively. However, the 1.0:5.0 ratio is more economical and was therefore selected. Based on the calculated extraction efficiencies, [BMIM]PF6 is a slightly more effective extracting agent.

The Lunpola Basin, developed during the Cenozoic era on the Tibetan Plateau, serves not only as a sedimentary record of plateau uplift but also as a significant reservoir of oil shale. This study focuses on the sedimentary environment of the oil shales in the Lunpola Basin and the enrichment mechanisms of trace elements, particularly hazardous elements, within them. A total of 38 samples were analyzed for major elements, trace elements, total organic carbon (TOC), and total sulfur (TS). Results show that several elements are significantly enriched relative to upper continental crust values, notably As (up to 45×), Mo (5.2×), Pb (3.8×), and U (3.3×). Geochemical proxies indicate deposition in a brackish to saline lacustrine setting, under predominantly anoxic to suboxic conditions, and in a warm–humid paleoclimate with moderate to low weathering intensity. Correlation analysis reveals that hazardous elements (As, Mo, Pb, U) are positively associated with TOC and TS, suggesting that organic matter and sulfide phases play key roles in their enrichment. Redox conditions appear to exert a primary control, while salinity and clay minerals contribute to secondary regulation. These results indicate that the enrichment of hazardous elements in the Lunpola oil shales is controlled by a combination of depositional environment and organic matter preservation, providing new insights into element cycling in continental lacustrine systems and implications for environmental risk during oil shale exploitation.

Oil shale from the Fushun West Open-pit Mine was selected as the research object to study the influence of heating rate on permeability. Through pyrolysis experiments at different heating rates, the evolution of permeability under various heating conditions was explored. Response surface methodology was used to optimize the pyrolysis parameters, and the optimal parameter combination was determined: a heating rate of 34.55 °C/min, a final reaction temperature of 475 °C, and a constant-temperature holding duration of 131 min. Under these conditions, the pyrolysis efficiency of Fushun oil shale was optimal. The key parameters identified provide a valuable reference for the in-situ exploitation of Fushun oil shale.