Oil shales from Attarat and Sultani were pyrolyzed at 550 °C to produce shale oils for the present study. The organic sulfur content of the two shale oils was determined to be 9.3 and 10.5 wt.%, respectively. Two ionic liquids (IL), 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) and 1-butyl-3-methylimidazolium thiocyanate ([BMIM]SCN), were used in liquid–liquid extraction for desulfurization. The extraction process was carried out at room temperature. The liquid–liquid extraction resulted in two-phase formation and redistribution of sulfur compounds into the aqueous IL-rich phase and the shale oil phase. The hydrocarbon sulfur weight percent was determined using a CHNSO analyzer. The removal efficiency for Sultani and Attarat shale oils with [EMIM]Cl was calculated to be 52.4 and 58.1 wt.%, respectively. When [BMIM]SCN was employed for the extraction of sulfur compounds from Sultani and Attarat shale oils, removal efficiencies of 43.8 and 52.4 wt.% were achieved, respectively. When the surfactant T-80 was added to Sultani shale oil and heated to 60 °C, followed by addition of [EMIM]Cl, the extraction efficiency decreased to 40.9 wt.%. On the other hand, when the mixture of shale oil and IL was heated to 60 °C before adding T-80, the weight percent removal increased to 58.1%.

Secondary raw materials, such as ashes from the combustion of various fuels, are frequently used as alternatives to virgin raw materials. Among these, oil shale ash, a residue from oil shale power production and the shale oil industry, presents significant potential for use in sectors such as construction and agriculture. However, these materials might contain hazardous substances, such as dioxins, which are by-products of thermal treatment and other industrial processes. To date, the dioxin content in oil shale ash has been insufficiently examined. This article provides a comprehensive analysis of the dioxin content in oil shale ash from both a pilot unit and full-scale facilities. Additionally, the study compares the dioxin concentrations in oil shale ash with those in other types of ash and evaluates compliance with regulatory limits. The results showed that dioxin concentrations in the ash were below the limit of detection, regardless of the combustion technology, plant capacity, use of supplementary fuels, or utilisation of wastewater. The findings contribute new knowledge by highlighting the environmental advantages of oil shale ash as a secondary raw material, particularly due to its comparatively lower dioxin content relative to other types of ash.

To determine the characteristics of the palaeoenvironment that affected organic richness, the Neogene organic-rich sediments in the Upper layer of the Aleksinac deposit (Dubrava block, Serbia) were examined. The studied samples are presumed to be of andesitic to felsic origin, with evidence of volcanic activity. Sediment generation was influenced by hydro-thermal fluids, which promoted the productivity of aquatic organisms and led to organic enrichment. Clastic input brought trace and rare earth elements into the basin. Palaeoenvironmental indicators derived from concentrations of major, trace, and rare earth elements show good accordance with organic geochemical data obtained in previous detailed studies, indicating deposition of the sediments in an anoxic lacustrine environment of variable salinity under warm, arid, and semiarid/semihumid climatic conditions. Such settings favoured primary bioproductivity in the lake, whereas a stable, stratified water column with highly reducing bottom water enhanced organic matter preservation. The lowering of total organic carbon content was mainly controlled by more humid episodes that promoted clastic influx and decreased organic matter concentration, rather than by changes in anoxic redox conditions.

This study focuses on the shale of the Lianggaoshan Formation in the Northeast Sichuan Basin, aiming to analyze the pore structure characteristics and influencing factors of its lithofacies – critical for shale oil exploration, as the area has seen major shale oil and gas exploration breakthroughs. Fresh outcrop shale samples were collected in the field, followed by experiments including polarized-light microscope thin-section identification, X-ray diffraction, total organic carbon analysis, gas adsorption, high-pressure mercury intrusion, and scanning electron microscopy. Four lithofacies were classified. Results show the shale contains micropores, mesopores, and macropores; total organic carbon correlates positively with micropore/mesopore parameters but negatively with macropores, while quartz content shows the opposite. The Frenkel–Halsey–Hill fractal dimension correlates positively with total organic carbon, feldspar, and clay minerals, and negatively with quartz. This provides a key theoretical basis for local Lianggaoshan Formation shale oil exploration.

The composition of inorganic matter and the enrichment of trace and rare earth elements (TEs and REEs) in the Neogene organic matter-rich sediments in the Upper layer of the Aleksinac deposit (Dubrava block, Serbia) were analysed. Correlation analysis clearly showed that TEs and REEs are associated with SiO2, Al2O3, K2O, and TiO2, clastic minerals, clay, and feldspar, as well as zeolite minerals natrolite and analcime, indicating that the TEs and REEs were brought into the basin mainly by clastic material. Their distribution indicates certain changes in the depositional environment during the formation of these sediments. According to enrichment factors (calculated in relation to World Oil Shales, Upper Continental Crust, and Post-Archaean Australian Shale) and the degree of enrichment (relative to argillaceous rocks), the Aleksinac oil shale shows significant enrichment in Mo, a lesser degree in Sr, and possible enrichment in Cu. Therefore, there are no concerns regarding toxic trace elements in the Aleksinac oil shale.

Oil shale in large basins undergoes multiple evolutionary stages, limiting the applicability of a single logging-based prediction model. This study focuses on the oil shale of the Qingshankou Formation in the Songliao Basin, using gamma ray (GR), deep resistivity (LLD), acoustic travel time (DT), neutron porosity (CNL), density (DEN), and depth data as input features. The XGBoost algorithm is employed to develop predictive models for total organic carbon (TOC) content, free hydrocarbon (S1), pyrolyzable hydrocarbon (S2), and maximum pyrolysis peak temperature (Tmax). TOC predictions are further stratified for low-maturity, mature, and high-maturity oil shale intervals. The results show that S2 achieves the highest prediction accuracy (R2 = 0.91), due to its strong correlation with hydrogen index (HI) driven by thermal evolution. TOC prediction accuracy (R2= 0.75) is influenced by combined changes in porosity and organic matter evolution. Tmax prediction (R2 = 0.74) depends mainly on depth and CNL. S1 correlates weakly with all well logs, yielding the lowest accuracy (R2= 0.29). Shale maturity plays a critical role in determining the reliability of TOC prediction models. Low-maturity oil shale exhibits the best TOC accuracy (R2= 0.83), as wellpreserved organic matter and high porosity correlate closely with LLD, DT, CNL, and DEN. In mature oil shale, retained hydrocarbon and reduced porosity weaken logging signals, lowering accuracy to R2 = 0.63. In high-maturity intervals, hydrocarbon expulsion and porosity rebound improve accuracy (R2 = 0.69). Our approach provides a cost-effective, continuous method for evaluating lacustrine oil shale resources. It is particularly applicable to the evaluation of uncored wells.

Oil shale is a type of unconventional energy with abundant reserves. In the in situ mining technology of oil shale, electric heating technology has become a research hotspot due to its multiple advantages, and electric heater is the core of this technology. Despite growing interest in electric heating for in situ oil shale extraction, there remains a lack of comprehensive reviews that focus specifically on the electric heater – its types, performance characteristics, and design optimization strategies. In this paper, the oil shale electric heater is taken as the research object. First, the four mainstream oil shale electric heating technologies – Shell’s in situ conversion process, ExxonMobil’s ElectrofracTM, geothermal fuel cell, and high-voltage power frequency electric heating technology – are analyzed, and their principles, characteristics, and limitations are elaborated in detail. Subsequently, the research status of electric heaters is discussed in depth, covering various types of heaters and their performance, and existing problems are identified. The key role of numerical simulation technology in the optimal design of electric heaters is emphasized. In the future, structural innovation and numerical simulation technology should be leveraged to further optimize the performance of oil shale electric heaters, continuously improving their heat efficiency, thereby promoting their extensive application in industrial fields.

This study investigates the mechanical properties of organic-rich shale from the Lianggaoshan Formation using uniaxial and triaxial tests, nanoindentation, and atomic force microscopy. Key parameters such as elastic modulus and hardness are analyzed with NanoScope Analysis software. The results indicate that flat-laminated shale outperforms corrugated-laminated shale in terms of fracturing potential. As laminae increase, rock strength decreases, enhancing fracability, while thicker laminae hinder fracturing. The elastic modulus trend is clay minerals > calcite > quartz > pyrite, with Young’s modulus negatively correlated with mineral deformation.

In situ conversion technology for oil shale is an innovative method of energy extraction that involves the underground heating of oil shale reservoirs to thermally crack kerogen into oil and gas. This approach avoids the environmental damage and high energy consumption associated with traditional mining methods and offers advantages such as reduced environmental impact, small ecological footprint, and low development costs. In this paper, a variety of in situ conversion technologies, including in situ conversion process (ICP), Electrofrac, geothermic fuels cells process (GFC), and supercritical water heating, are discussed in detail. The paper also analyzes the current state and development trends of in situ conversion technologies in China, and highlights the importance of advancing basic theoretical research and overcoming key technologies to enable large-scale utilization of oil shale resources. Continued research and improvement in in situ conversion technologies will enhance both the efficiency and sustainability of the energy industry.

This study focuses on shale samples from the medium-deep lacustrine shale in the third member of the Shahejie Formation, Bohai Bay Basin. Thermal simulation experiments were conducted using gold tubes to study hydrocarbon generation. The results indicate that shale biomarkers vary at different thermal evolution stages and provide distinct geochemical indications. Compared with saturated hydrocarbons, aromatic hydrocarbon parameters can better indicate the maturity of high- to overmature crude oil. The correlation between the parameters of aromatic hydrocarbon -biomarkers and the maturity of crude oil is as follows: methylphenanthrene parameters (MPI1), 4-MDBT/1-MDBT, perene/benzo[e]pyrene, methylphenanthrene ratio (MPR), benzofluoranthene/benzo[e]pyrene, trimethylnaphthalene ratio (TMNr), and tetramethylnaphthalene ratio (TeMNr). The variation in several parameters indicates that 345–445 °C is thepeak oil generation window (the corresponding Ro is about 0.6–1.3%), during which hydrocarbon expulsion efficiency increased greatly, and residual hydrocarbons accumulate -massively. This research provides a basis for evaluating shale oil and gas resources. Shale with a vitrinite reflectance of 0.6–1.3% is the most beneficial for exploration and development.