This study employs the computational particle fluid dynamic model to simulate a 65 t/h oil shale-fired high-low differential velocity circulating fluidized bed (CFB) boiler. The effects of the excess air ratio on furnace temperature, gas composition, particle residence time, and pollutant emissions were analyzed. Results show that an excess air ratio of 1.10 intensifies particle back-mixing, enhancing combustion while reducing NO and SO2 emissions. The optimal condition combines this ratio with a 1.5:1 main/side bed air distribution, achieving the lowest emissions. This work provides valuable insights for optimizing CFB boiler operation.
To enhance heat transfer between shale ash and oil shale particles in a rotary retorting furnace, this study coupled the discrete element method (DEM) with a particle heat conduction model to simulate mixing and heat transfer, examining the effects of particle filling ratio, furnace rotational speed, and baffle structures. A backpropagation neural network (BP-NN) model was built from simulation data to map furnace operation time with key parameters, and a genetic algorithm was used to optimize parameters to minimize operation time. The research results show that lower filling degrees and higher rotation speeds significantly strengthen particle mixing and heat exchange, which accelerate the systemâs stabilization, improve temperature field uniformity, and reduce the temperature standard deviation. The mixing and heat transfer effect of the straight baffle is between that of the right-angle baffle and the inclined baffle, but it causes the largest temperature standard deviation. In contrast, the right-angle baffle demonstrates stronger advantages in heat transfer uniformity during particle lifting and throwing. The constructed BP-NN prediction model achieves a relative error accuracy within 0.25%, effectively solving the long computation time problem of DEM simulation. The optimized parameter combination provides a theoretical basis for the development of high-efficiency and energy-saving rotary retorting furnaces.
Derivatization of the kerogen backbone changes its chemical reactivity profile. In this study, kukersite kerogen was methylated with dimethyl carbonate. The substance was analyzed before and after processing by Fourier transform infrared spectroscopy, 13C cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and elemental analysis. It was observed that kukersite kerogen can be readily methylated with dimethyl carbonate. Based on mass balance and the Lille-Blokker model, an average of 19 methyl groups were added to the kerogen unit. It was concluded that about half of the hydroxyl groups in Estonian kukersite kerogen are âfreeâ and accessible to methylation.
To optimize the oil shale retorting process and improve the thermal efficiency of the retort, a heat transfer model of the oil shale retorting in the Fushun-type retort was established based on the gas-solid heat transfer equation. The orthogonal experimental method was used, with hot air volume (A), hot recycle gas temperature (B), and oil shale interparticle porosity (C) taken as the investigation factors, and the retort height required for the retorting of the same quality oil shale as the metric of the thermal efficiency of the retort. The smaller the retort height, the higher the thermal efficiency of the retort. Range and variance analyses revealed that the effects of the three factors on retort height are, from large to small: A > B >C; this shows that hot air volume (A) exerts the most significant influence. Based on this, computational fluid dynamics simulation was conducted on the hot air volume parameter. The study shows that increasing the hot air volume can effectively increase the heat supply proportion of the generated gas in the retorting process to 59.288%. To maintain the height of the high-temperature zone in the reaction section, it is proposed to increase the oxygen content in the hot air volume, which proves the feasibility of oxygen-enriched retorting.
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 liquidâliquid extraction for desulfurization. The extraction process was carried out at room temperature. The liquidâliquid 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%.
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.
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.
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 â 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 FrenkelâHalseyâHill 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.
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 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 degrees C is the peak oil generation window (the corresponding Ro is about 0.6-1.39), 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 0.6-1.39 is the most beneficial for exploration and development.
In Estonian oil shale power plants, ash is transported to disposal sites using a wet transport method. Due to regional climatic conditions, where annual precipitation exceeds evaporation, part of the recirculated ash transport water has to be periodically discharged into natural surface waters. This discharge practice raises concerns about the potential environmental impact of the discharged water. This paper investigates the leaching behavior of several trace elements from oil shale ash, demolition wood ash, and their mixtures, with a focus on chromium. In particular, the occurrence, mobility, and oxidation state of chromium in the leachate are considered using the example of the mentioned ashes. The possible effect of ash content, influenced by fuel type and the liquid-to-solid (L/S) ratio, on trace element concentrations in the discharged water was studied. In leaching tests with 100% oil shale ash, the chromium concentration in the circulating water increases only slightly when circulating water from the oil shale ash field is used as the leaching medium. On the one hand, the amount of chromium and other trace elements leached from oil shale ash depends on the L/S ratio. At the same time, it is known from the literature that oil shale ash is also capable of binding chromium. The release and concentration of chromium in the leachate increase significantly as the proportion of waste wood ash rises, compared to tests using 100% oil shale ash. Consequently, the concentration of chromium in surface water, depending on the specific ratio of oil shale to waste wood used in co-combustion, can easily exceed the nationally permitted limit value.
Oil shale, a significant fossil energy source, has garnered global attention due to its huge reserves and potential as an alternative to conventional petroleum. This minireview evaluates the comprehensive utilization of oil shale, focusing on its entire lifecycle, from extraction to energy production, treatment of abandoned mines, and subsequent utilization to gain more economic and environmental benefits. In addition, the minireview underscores the necessity of green and high-value utilization of oil shale and its by-products (i.e., semicoke and ash) to mitigate environmental pollution. To promote comprehensive utilization of oil shale and its by-products, we summarize current knowledge extending beyond traditional energy applications to encompass construction materials, environmental functional materials, and other high-value products. Strategies such as circulating fluidized bed combustion, in situ conversion, and co-combustion and co-pyrolysis with biomass are introduced for efficient resource use. The treatment of abandoned oil shale mines for energy storage and the recovery of trace and rare earth elements are also addressed. The minireview concludes with recommendations for improving testing strategies, assessing environmental impacts, and exploring new applications to ensure green and sustainable development in the oil shale industry.
This study analyzed 25 Chang 7 shale samples from the Ordos Basin, examining geochemical properties, mineral composition, nitrogen adsorption, mercury injection capillary pressure, and NMR T-2 and T-1-T(2 )spectra. The results indicate that the shale primarily contains type II1 and II2 kerogen, with mature thermal maturity. Organic-rich shales are enriched in clay and felsic minerals, while organic-lean shales show more dispersed mineral compositions. Nitrogen adsorption classified the shale into four types, with type H2 showing the best properties. The study developed pore size conversion models and clarified the occurrence characteristics of hydrogen nucleus components, providing valuable insights for NMR evaluation of shale reservoirs globally.
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 Youngâs modulus negatively correlated with mineral deformation.
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 â 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 â Shellâs in situ conversion process, ExxonMobilâs ElectrofracTM, geothermal fuel cell, and high-voltage power frequency electric heating technology â 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.
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.
The in situ heater, a pivotal component for oil shale heating, is prone to deformation at underground temperatures of up to 450 °C. While lab experiments with optical fiber technology can monitor deformation at temperatures up to 1100 °C, low-pressure tolerance and complex manufacturing hinder its underground application. Current downhole monitoring systems are limited to 300 °C for temperature and 100 °C for deformation, which are insufficient for oil shale conditions. A dedicated online monitoring system for in situ heaters is still lacking. Leveraging the precision and reliability of linear variable differential transformer (LVDT) technology, we designed a real-time deformation monitoring system. Indoor simulations mimicking oil shale environments indicate LVDTâs capability of monitoring up to 480 °C. The system mounts an LVDT unit, encapsulated in vacuum insulation, onto heaters, and then inserts them into horizontal sections via tubing. This design offers a valuable reference for the design and monitoring of in situ heaters in oil shale wells.
Significant progress has been made in the exploration and development of oil shale in Sinopecâs K-II block. However, frequent downhole blockages, drilling incidents, and wellbore instability have posed challenges for high-inclination horizontal drilling. This study analyzes complex subsurface conditions using field data and core experiments to investigate the physical, chemical, and mechanical properties of the formation. Key factors driving oil shale collapse are identified, and a wellbore stability evaluation method for the Shahejie Formation is developed. Results show that the formation has well-developed fractures, with quartz and clay as its primary components, and that water-based drilling fluids have minimal impact on its mechanical properties. Wellbore stability is significantly affected by inclination, azimuth, and weak-plane fractures. The critical collapse pressure equivalent density ranges from 1.5 to 1.65 g/cm3. Drilling along the maximum horizontal stress improves stability compared to drilling along the minimum stress. Enhancing drilling fluid sealing and adding rigid particles further improve wellbore integrity. These findings provide practical insights for safer oil shale drilling operations.
This study introduces a novel visual online observation technique for identifying the critical temperature for oil generation. It also examines the hydrocarbon generation properties of Maoming oil shale when subjected to supercritical water. Findings indicate that the critical temperature for Maoming oil shale in supercritical water ranges from 262 to 292 °C, and the visualization reactor facilitates the investigation of this critical temperature. The organic carbon conversion rate for Maoming oil shale can exceed 25.4% within a limited reaction time of one hour. Increasing the water-shale mass ratio enhances the overall conversion of organic carbon in the oil shale and boosts oil production, although it does not significantly improve gas production. Additionally, a higher water-shale mass ratio can decrease the heavy oil fraction in the oil and enhance the selectivity for hydrogen and methane in the gas produced.
