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The anisotropic fracture characteristics of oil shale are crucial in determining reservoir modification parameters and pyrolysis efficiency during in situ oil shale pyrolysis. Therefore, understanding the mechanisms through which temperature and bedding planes influence the fracture behavior of oil shale is vital for advancing the industrialization of in situ pyrolysis technology. In this study, scanning electron microscopy (SEM), CT scanning, and a real-time high-temperature rock fracture toughness testing system were utilized to investigate the spatiotemporal evolution of pores and fractures in oil shale across a temperature range of 20–600 °C, as well as the corresponding evolution of fracture behavior. The results revealed the following: (1) At ambient temperature, oil shale primarily contains inorganic pores and fractures, with sizes ranging from 50 to 140 nm. In the low-temperature range (20–200 °C), heating primarily causes the inward closure of inorganic pores and the expansion of inorganic fractures along bedding planes. In the medium-temperature range (200–400 °C), organic pores and fractures begin to form at around 300 °C, and after 400 °C, the number of organic fractures increases significantly, predominantly along bedding planes. In the high-temperature range (400–600 °C), the number, size, and connectivity of matrix pores and fractures increase markedly with rising temperature, and clay minerals exhibit adhesion, forming vesicle-like structures. (2) At room temperature, fracture toughness is highest in the Arrester direction (KIC-Arr), followed by the Divider direction (KIC-Div), and lowest in the Short-Transverse direction (KIC-Shor). As the temperature increases from 20 °C to 600 °C, both KIC-Arr and KIC-Div initially decrease before increasing, reaching their minimum values at 400 °C and 500 °C, respectively, while KIC-Shor decreases continuously as the temperature increases. (3) The energy required for prefabricated cracks to propagate to failure in all three directions reaches a minimum at 100 °C. Beyond 100 °C, the absorbed energy for crack propagation along the Divider and Short-Transverse directions continues to increase, whereas for cracks propagating in the Arrester direction, the absorbed energy exhibits a 'W-shaped' pattern, with troughs at 100 °C and 400 °C. These findings provide essential data for reservoir modification during in situ oil shale pyrolysis. [ABSTRACT FROM AUTHOR]

Sealing is an important prerequisite for downhole heater work. This paper proposes a combination of soft and hard, and welding sealing programs, which were analysed using theoretical calculations, numerical simulation, and in-situ testing. The results show that 316 stainless steel can meet the stuffing seal requirements. The first stuffing leads to compression and gradual reduction, while the second stuffing essentially does not deform. Stuffing deformation fills the gap in the sealing hole, creating a sealing layer. The compression rate is 0.43%, 8.45%, and 12.64%, indicating that the locking stress should be more than 2000 N. The temperature at the weld is heated by heat conduction and distributed in a concentric circle. Thermal stress will influence the 50 mm barrier, but the 100 mm boundary will be mostly unaffected. Actually, the thermal stress that destroys the weld seal may be reduced by adjusting the heater output or raising the gas injection rate. During the beginning of the in-situ heat injection, the temperature of the heating rods rises simultaneously with the outlet temperature. Consequently, both show opposite tendencies. The heat generated by the heating rods will cause the injected gas to be preheated in advance. [ABSTRACT FROM AUTHOR]

Jordan's energy sector faces significant challenges due to rising fuel prices, making the exploration of local energy resources crucial. The abundant oil shale deposits in Wadi Thamad present a promising opportunity. Since Wadi Thamad oil shale has never been studied before, this research focuses on the Wadi Thamad basin near Madaba, Jordan, aiming to comprehensively characterize its oil shale using advanced analytical techniques. Using X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray fluorescence, scanning electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry, this study assesses the mineralogical, chemical, and thermal properties of Wadi Thamad oil shale. The findings reveal calcite and quartz as the primary minerals, with significant aliphatic, CO2, hydroxyl, and carboxyl groups. Elemental analysis highlights essential oxides, such as CaO and SiO2. Fischer assay results indicate an oil content of 5.3–10.1 wt%, a gross‐calorific value of 4.56–7.69 MJ/kg, and a sulfur content of 1.77–2.10 wt%. The peak pyrolysis temperature is 432.4°C from TGA. This research's novelty lies in its comprehensive approach to characterizing the underexplored Wadi Thamad oil shale basin. The findings enhance the understanding of Wadi Thamad's geological composition and underscore its potential as a local energy resource, contributing valuable data to Jordan's energy portfolio and offering economic benefits. [ABSTRACT FROM AUTHOR]

The effect of particle packing height (10, 30, 50, 70 mm) on the yield and composition of oil shale pyrolysis products is investigated. The results show that the oil yield could decrease 1.0% and the noncondensable gases yield could increase 0.5% as the oil shale packing height increased from 10 to 70 mm. The main hydrocarbon gases are C1–C6 gases, and the increase of packing bed height could decrease the relative content ratio of alkanes to alkenes in hydrocarbon gases. The primary components of the derived oil are aliphatic compounds, aromatic compounds, and compounds containing heteroatoms in the carbon atoms range of C6–C28. And the hydrogen type of shale oil is mainly composed of methylene groups (about 70%) with longer alkyl chains, and CH3 in aromatics, cycloalkanes, and alkanes. The chemical composition and hydrogen type have certain regularity changes with the changing of packing height, attributing to the effect of temperature gradients between surface and center of packing bed, and the diffusing time of products through the packing bed. [ABSTRACT FROM AUTHOR]

This review discusses recent research findings spanning the last two decades concerning ultrasonic technologies applicable to the oil, gas, and coal sectors. Various experiments conducted in laboratories have demonstrated the efficacy, cost-effectiveness, and environmental friendliness of ultrasound in recovering and processing oil, bitumen, coal, and oil shale. Ultrasound enhances formation permeability, coal gas permeability, and oil viscosity, particularly when delivered in short, powerful pulses at medium frequencies. Combining ultrasound with traditional recovery methods has shown promising results, boosting recovery efficiency by up to 100%. At the same time, ultrasonic treatment reduces the use of traditional reagents, thereby reducing environmental pollution. Moreover, ultrasound treatment shows potential in tasks such as separating oil–water emulsions, desulfurization, dewaxing oil, coal enrichment, and extracting valuable metals from metal-bearing shales through hydrometallurgical leaching. However, the widespread industrial implementation of ultrasonic technology necessitates further field and mathematical research. [ABSTRACT FROM AUTHOR]

This investigation focuses on the prevalent continental oil shale within the Triassic Chang 7, a member of the Yanchang Formation in the Ordos Basin and the Permian Lucaogou Formation in the Junggar Basin of western China, and delves into the impacts of hydrocarbon generation and the derived organic acids on the physical attributes of oil shale reservoirs. Water-soluble organic acids (WSOAs) were extracted via Soxhlet extraction and analyzed by a 940 ion chromatograph (Metrohm AG), supplemented with core observations, thin-section analyses, pyrolysis, and trace element assays, as well as the qualitative observation of pore structures via FIB-SEM scanning electron microscopy. The study discloses substantial disparities in the types and abundances of organic acids within the oil shale strata of the two regions, with mono-acids being conspicuously more prevalent than dicarboxylic acids. The spatial distribution of organic acids within the oil shale strata in the two regions is non-uniform, and their generation is inextricably correlated with the type of organic matter, thermal maturity, and depth at which they are buried. During diverse stages of diagenesis, the hydrocarbons and organic acids produced from the pyrolysis of organic matter not only exert an impact on the properties of pore fluids but also interact with diagenetic processes such as compaction, dissolution, and metasomatism to enhance the reservoir quality of oil shale. The synergy between chemical interactions and physical alterations collectively governs the migration and distribution patterns of organic acids as well as the characteristics of oil shale reservoirs. Furthermore, the sources of organic acids within the oil shale series in the two regions demonstrate pronounced dissimilarities, which are intimately associated with the peculiarities of their sedimentary milieu. The oil shale of the Yanchang Formation was formed in a warm and humid freshwater lacustrine basin environment, while the oil shale of the Lucaogou Formation was deposited in a brackish to saline lacustrine setting under an arid to semi-arid climatic regime. These variances not only illuminate the intricacy and multiplicity of the sedimentary attributes of oil shale but also accentuate the impact of the sedimentary environment on the genesis and distribution of organic acids, especially the transformation and optimization of reservoir dissolution by organic acids generated during hydrocarbon generation—a factor of paramount significance for the precise identification and effective development of the "sweet spot" area of shale oil. These areas, characterized by an abundance of organic matter, their maturity, and superior reservoir properties, are the foci of the efficient exploration and development of continental shale oil. [ABSTRACT FROM AUTHOR]

The results of derivatographic studies of the decomposition of oil shale and thermolysis processes in the presence of oil shale are presented. It was found that the addition of oil shale to brown or hard coal intensified the process of thermal dissolution of coal, and the solubility of the organic matter of coal increased with the amount of added oil shale; gas formation decreased and the yield of liquid products increased. The activating role of oil shale was also revealed in the processes of thermolysis of oil residues, gasification (high-temperature thermolysis) of fuel oil and tar emulsions, and preparation of bitumen compositions for road construction. [ABSTRACT FROM AUTHOR]

The detection and quantitative analysis of shale components are of great significance for comprehensively understanding the properties of shale, assessing its resource potential and promoting efficient development and utilization of resources. The low-field NMR T1-T2 two-dimensional spectrum can detect shale components non-destructively and effectively. Unfortunately, due to its complexity, the two-dimensional spectral results of low-field NMR are mainly analyzed using manual qualitative analysis, and accurate results of the composition cannot be obtained. Since the information contained in its two-dimensional map is determined by the morphological texture and the position in the map, commonly used image analysis networks cannot adapt. In order to solve these problems, this paper improves a novel Faster Region-based Convolutional Neural Network (Faster-RCNN). Compared with previous models, the improved Faster-RCNN has better image classification and visual key point estimation capabilities. The results show that compared with traditional methods, the deep learning method using this model can directly obtain key information such as kerogen and movable oil and gas content in rocks. The information provided in this study can help complement and improve the development of analytical methods for low-field 2D NMR spectra. [ABSTRACT FROM AUTHOR]

Copyright of Oilfield Chemistry is the property of Sichuan University, Oilfield Chemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon capture, utilization, and storage (CCUS) have emerged as pivotal technologies for curtailing emissions while maintaining fossil fuel. Estonia faces a challenge due to its dependence on carbon-intensive oil shale, but the need for energy security, highlighted by the war in Ukraine, makes reducing CO2 emissions a priority while maintaining energy independence. In this context, the presented study determines the environmental impact of combustion of the Estonian oil shale from the release of SO2 emission and compares sulfur retention in the ash between different oxyfuel combustion campaigns in a 60 kWth CFB test facility. The pilot was operated under air, O2/CO2, and with recycled flue gas (RFG), and we tested the application of extremely high inlet O2 up to 87%vol. The key objective of this study is to examine how different combustion atmospheres, operating temperatures, and excess oxygen ratios influence SO2 formation. Additionally, the research focuses on analyzing anhydrite (CaSO4), calcite (CaCO3), and lime (CaO) in ash samples collected from the dense bed region (bottom ash) and the external heat exchanger (circulating ash). The results indicate that increased inlet O2% does not significantly affect SO2 emissions. Compared to air-firing, SO2 emissions were higher than 40 mg/MJ under a 21/79%vol O2/CO2 environment but were significantly reduced, approaching zero, as the inlet O2% increased to 50%. Under O2/RFG conditions, higher SO2 concentrations led to increased sulfur retention in both the bottom and circulating ash. The optimal temperature for sulfur retention in air and oxyfuel combustions is below 850 °C. This study for the first time provides a technical model and discusses the effects of operating parameters on sulfur emissions of the Estonian oil shale CFB oxyfuel combustion. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Jordan's energy sector faces significant challenges due to rising fuel prices, making the exploration of local energy resources crucial. The abundant oil shale deposits in Wadi Thamad present a promising opportunity. Since Wadi Thamad oil shale has never been studied before, this research focuses on the Wadi Thamad basin near Madaba, Jordan, aiming to comprehensively characterize its oil shale using advanced analytical techniques. Using X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray fluorescence, scanning electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry, this study assesses the mineralogical, chemical, and thermal properties of Wadi Thamad oil shale. The findings reveal calcite and quartz as the primary minerals, with significant aliphatic, CO2, hydroxyl, and carboxyl groups. Elemental analysis highlights essential oxides, such as CaO and SiO2. Fischer assay results indicate an oil content of 5.3–10.1 wt%, a gross‐calorific value of 4.56–7.69 MJ/kg, and a sulfur content of 1.77–2.10 wt%. The peak pyrolysis temperature is 432.4°C from TGA. This research's novelty lies in its comprehensive approach to characterizing the underexplored Wadi Thamad oil shale basin. The findings enhance the understanding of Wadi Thamad's geological composition and underscore its potential as a local energy resource, contributing valuable data to Jordan's energy portfolio and offering economic benefits.

Abstract The effect of particle packing height (10, 30, 50, 70 mm) on the yield and composition of oil shale pyrolysis products is investigated. The results show that the oil yield could decrease 1.0% and the noncondensable gases yield could increase 0.5% as the oil shale packing height increased from 10 to 70 mm. The main hydrocarbon gases are C1–C6 gases, and the increase of packing bed height could decrease the relative content ratio of alkanes to alkenes in hydrocarbon gases. The primary components of the derived oil are aliphatic compounds, aromatic compounds, and compounds containing heteroatoms in the carbon atoms range of C6–C28. And the hydrogen type of shale oil is mainly composed of methylene groups (about 70%) with longer alkyl chains, and CH3 in aromatics, cycloalkanes, and alkanes. The chemical composition and hydrogen type have certain regularity changes with the changing of packing height, attributing to the effect of temperature gradients between surface and center of packing bed, and the diffusing time of products through the packing bed.

Oil shale, the most important unconventional oil and gas reservoir resource, is characterized by large geological reserves, difficult development technology, and great development potential. Although it cannot be exploited in a large area due to cost issues, with the development and utilization of conventional oil and gas reservoir resources, it is the main direction of future oil exploitation. Based on the classification of in situ conversion technologies of oil shale electric heating into in situ conversion process technology, ElectrofracTM technology, geothermal fuel cell heating technology, high-voltage power frequency electric heating technology, and other electric heating technology, this paper summarizes the research progress on existing electric heating technologies to provide a reference for the engineering research and development of oil shale electric heating in situ mining technology.

Abstract This article proposes an in-situ steam-assisted thermal decomposition method for oil shale using long-distance horizontal wells.Firstly, this article establishes a coupled thermal–hydraulic hydrothermal mechanical model considering the anisotropy of oil shale to study the in-situ pyrolysis process of oil shale by steam injection in horizontal wells. Then Optimization analysis was conducted on the effects of fracture spacing, fracture length, and horizontal well length on extraction efficiency. Finally, An economic analysis was conducted on the new extraction method. The research results indicate that: (1) Compared with the traditional vertical well mining mode (1injection and 8 production well, with a well spacing of 50 m), the newly proposed long-distance horizontal well configuration (1 injection and 2 production well) has higher heating efficiency. (2) When the fracture spacing is less than 25 m, the heating efficiency is no longer significantly improved. Increasing the length of fractures has a significant effect on improving heating efficiency. (3) When the length of the horizontal well exceeds 450 m, the extraction cost no longer significantly decreases. Increasing the length of fracturing fractures can significantly reduce extraction costs. When the fracture spacing is less than 30 m, the extraction cost no longer significantly decreases. This study provides theoretical reference and data support for the efficient in-situ thermal decomposition of oil shale.

A co-pyrolysis of woodchips and oil shale was conducted in a continuous reactor at 520 °C in a CO2 atmosphere. Experimental product yields were derived and an analysis of the liquid products was conducted, using gas chromatography, infrared spectroscopy, and physicochemical analysis. A maximum yield of liquids and gases was obtained as the share of biomass increased (43.9 and 35.1 wt%, respectively). Product characterization confirmed additive behavior in co-pyrolysis. The liquid products from co-pyrolysis blends exhibited fewer oxygenated compounds, derived from biomass, and fewer aromatic compounds, derived from oil shale. Co-pyrolysis liquids contained abundant aliphatic hydrocarbons (C6 to C11).

To analyze the heat transfer characteristics of oil shale under different in situ pyrolysis methods from a microscopic perspective, a combination of experimental and simulation approaches was employed. Initially, high-temperature in situ pyrolysis experiments on single-fracture oil shale were conducted using high-temperature steam and electrical methods. Subsequently, micro-CT scanning technology was utilized to obtain digital rock cores under different in situ pyrolysis conditions. Finally, these digital rock cores were seamlessly integrated with COMSOL 6.0 to achieve numerical simulations of high-temperature steam convective heating and electrical conductive heating in the in situ state. The relevant conclusions are as follows: Firstly, during the in situ pyrolysis of oil shale with high-temperature steam convective heating, the overall temperature increase is uniform and orderly. Heat is conducted gradually from the pores and fractures to the matrix. The uneven distribution of pores and fractures causes an uneven temperature field, but no localized overheating occurs, which can effectively enhance the pyrolysis efficiency. Secondly, the heat transfer direction in electrical conductive heating is primarily inward along the normal direction of the heat source end face. The closer the section is to the heat source end face, the higher the rate of temperature increase. Within 1 s, the temperature rise at 100 μm (near the heat source end face) is 2.27 times that at 500 μm (near the farthest cross-section from the heat source end face). The heat transfer effect of high-temperature steam convective heating consistently surpasses that of electrical conductive heating. The Tc value initially increases and then decreases as pyrolysis progresses, reaching a maximum of 1.61331 at 0.4 s, but Tc remains greater than 1 throughout. Finally, in the initial stages of pyrolysis, the high-temperature region formed by conductive heating is superior to that of convective heating. However, once the heat carrier fluid flow stabilizes, the volume of the high-temperature region formed by convective heating grows rapidly compared to that of conductive heating. At 1 s, the volume of the high-temperature region formed by convective heating reaches 5.22 times that of the high-temperature region formed by conductive heating. [ABSTRACT FROM AUTHOR]

Real-time high-temperature CT scanning and a rock-mechanics test system were employed to investigate the mechanical properties of oil shale at temperatures from 20 to 600 °C. The results reveal that up to 400 °C, the aperture of fractures initially decreases and then increases when loading is perpendicular to the bedding. However, the number and aperture continuously increase when loading is parallel to the bedding. Beyond 400 °C, the number of pores increases and the aperture of the fractures becomes larger with rising temperature. The changes in microstructures significantly impact the mechanical properties. Between 20 and 600 °C, the compressive strength, elastic modulus, and Poisson's ratio initially decrease and then increase under perpendicular and parallel bedding loadings. The compressive strength and elastic modulus reach minimum values at 400 °C. However, for Poisson's ratio, the minimum occurs at 500 °C and 200 °C under perpendicular and parallel bedding loadings, respectively. Simultaneously, while the crack damage stress during perpendicular bedding loading, σcd-per, initially exhibits an upward trend followed by a decline and subsequently increases again with temperature increasing, the initial stress during perpendicular bedding loading, σci-per, parallel bedding loading, σci-par, and damage stress, σcd-par, decrease initially and then increase, reaching minimum values at 400 °C. These research findings provide essential data for reservoir reconstruction and cementing technology in the in situ mining of oil shale. [ABSTRACT FROM AUTHOR]

With the gradual depletion of conventional petroleum resources, oil shale, as an important unconventional oil and gas resource, is of great significance to alleviate the global energy crisis and optimize the energy structure. In this study, we comprehensively assessed the organic matter abundance, type, maturity, and trace element characteristics of oil shale by collecting and analyzing oil shale samples from the Lower Permian region in the western part of the southern margin of the Junggar Basin, and by applying pyrolysis analysis and rock pyrolysis analysis. The study showed that the average value of total organic carbon (TOC) of the oil shale in the study area was 10.26%, of which 41.67% was medium-grade oil shale and 58.33% was low-grade oil shale, reflecting the overall abundance of medium-low organic matter. The average value of hydrocarbon potential was 40.83 mg/g. The hydrogen index of the oil shale samples ranged from 77 to 861.06 mg/g, with an average value of 405.56 mg/g. The organic matter type was mainly of the II1 type (humic-sapropelic type), which accounted for 75% of the total, and the analysis of the highest pyrolysis peak temperature showed that 83.33% of the samples were in the low maturity-mature stage. Trace element analyses revealed that the oil shales in the study area were formed in a terrestrialweakly reduced depositional environment. Especially, the analysis of Sr/Ba, Th/U and B/Ga ratios indicated that the oil shale was mainly formed in freshwater-semi-saline environment. In addition, the analysis of V/(V+Ni) and U/Th ratios supports the reduced environment in which the oil shale was formed. The shale in the Dalongkou area has greater salinity values and higher organic matter productivity in the water body at the time of formation compared to the oil shale in the Cangfanggou area. The results of this study are important for understanding the geochemical properties and mineralization potential of the Lower Permian oil shales in the western part of the southern margin of the Junggar Basin. [ABSTRACT FROM AUTHOR]

Grinding is an indispensable process in many industrial plants. Nonetheless, the ground products may pass through the surface and/or undergo structural changes that may affect subsequent processes. In this study, the changes in the oil shale surface during its dry grinding in a ball mill were followed by Fourier-transform infrared (FTIR) analysis under different grinding conditions such as grinding time, ball type (i.e. ceramic or steel), and number of balls. Moreover, the generated heat limits during grinding were revealed by correlating the change in surface function groups of the ground products with those of conventionally heated oil shale samples in a furnace. The results indicated that the more intense the grinding action, in terms of the number or size of grinding balls and the grinding time, the higher the variations in the ground products' FTIR spectra, indicating the higher the surface oxidation of oil shale. More interestingly, correlating the FTIR spectra of the heated samples with those of the ground products indicated that the temperature inside the mill does not exceed 150 °C. [ABSTRACT FROM AUTHOR]

The co-combustion characteristics of furfural residue (FR) and oil shale (OS) were investigated in a thermogravimetric analyzer under different heating rate (10, 30, 50 °C/min) and mixing ratio (1:0; 3:1; 1:1; 1:3; 0:1). The effects of synergy was estimated by using the interaction coefficient, and the kinetics were looked at using the Coats-Redfern method in the co-combustion of furfural residue (FR) and oil shale (OS). To obtain the maximum the flammability index (C) and comprehensive combustion characteristic index (CCI), and minimum activation energy (Em), the response surface method (RSM) was employed to find the best mixing ratio and heating rate. The ignition temperature (T1) and burnout temperature (T2) went down as the FR mixing ratio went up, but the fuel's highest burning rate (Rmax), the average burn rate (Ra), C, and CCI of mixed samples went up as the FR mixing ratio went up. The sample's T1, T2, Rmax, Ra, C, and CCI all went up as the heating rate went up. As the rate of heating went up, E of combustion went down. E of mixed fuel combustion was lower than E of FR combustion alone, which showed that there were interactions in the mixed combustion. The effects of this synergy were clearer when the temperature was higher. According to the model optimization, the optimal conditions were obtained. [ABSTRACT FROM AUTHOR]

A co-pyrolysis of woodchips and oil shale was conducted in a continuous reactor at 520 °C in a CO2 atmosphere. Experimental product yields were derived and an analysis of the liquid products was conducted, using gas chromatography, infrared spectroscopy, and physicochemical analysis. A maximum yield of liquids and gases was obtained as the share of biomass increased (43.9 and 35.1 wt%, respectively). Product characterization confirmed additive behavior in co-pyrolysis. The liquid products from copyrolysis blends exhibited fewer oxygenated compounds, derived from biomass, and fewer aromatic compounds, derived from oil shale. Co-pyrolysis liquids contained abundant aliphatic hydrocarbons (C6 to C11). [ABSTRACT FROM AUTHOR]

Oil shale is a critical strategic resource with enormous reserves. In-situ combustion technology offers great potential for the development of oil shale reserves. In this study, the combustion behavior and kinetics of Domanik oil shale were investigated using High Pressure Differential Scanning Calorimetry. Additionally, the thermal behavior of the oil shale during combustion was studied by using a self-designed Porous Medium Thermo-Effect Cell. Furthermore, the stability of the combustion front and the upgrading effect of the combustion process were investigated with Visual Combustion Tube, and the produced oil was analyzed to evaluate its quality. The results showed that the combustion process of oil shale is characterized by two reaction stages. The oil shale was found to form enough coke residue during the oxidation reactions to allow for stable propagation of a combustion front. The produced oil was of better quality compared to the naturally produced bitumen in oil shale, which indicates that the combustion process had a good upgrading effect. The findings of this study provide a better understanding of the in-situ upgrading process of kerogen and provide significant knowledge about the combustion mechanism of oil shale for its potential development using the in-situ combustion technology. [ABSTRACT FROM AUTHOR]

This study studies the effect of flow and thermal transfer properties of fluids with varying densities, viscosities, and thermal conductivities on the performance of oil shale in-situ conversion process based on multi-physics coupling simulation. Results indicate that thermal convection primarily governs the heat transfer process in oil shale. Consequently, to enhance the pyrolytic effects, fluids possessing high density, low viscosity and superior thermal conductivity are recommended. This research thus provides a foundational understanding for the selection of fluid properties in the in-situ extraction of oil shale. [ABSTRACT FROM AUTHOR]

The Carnian Pluvial Episode (CPE) fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province (LIP). However, the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood. Records of negative carbon isotopic excursions (NCIEs), mercury (Hg), Hg/TOC, and Hg enrichment factor (HgEF) from oil shales in a large‐scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions. The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe, the UK, and South and North China. The U‐Pb geochronology indicates a Ladinian–Carnian age for the Chang 7 Member. A comprehensive overview of the geochronology, NCIE correlation, and previous bio‐ and chronostratigraphic frameworks shows that the Ladinian–Carnian boundary is located in the lower part of Chang 7 in the Yishicun section. HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions. The records of Hg, Hg/TOC, HgEF, and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies, indicating a global response to the Wrangellia LIP during the CPE. Anoxia, a warm‐humid climate, enhancement of detrital input, and NCIEs are synchronous with the CPE interval in the Ordos Basin, which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin. [ABSTRACT FROM AUTHOR]

Steam convective heating emerges as a sustainable and effective method for extracting oil shale, where understanding the temperature-dependent evolution of its pyrolytic characteristics, microstructure, and permeability is vital for efficient resource extraction. Through a stress-sensitive micro-CT scanning and a high-temperature and pressure triaxial test apparatus, this research utilizes Balikun oil shale samples to investigate the changes in microstructure and gas production from 20 °C to 550 °C. The study integrates theoretical analysis and numerical simulations to uncover the fundamental connections between internal permeability and heat transfer mechanisms during steam injection. It reveals that oil shale undergoes two critical evolutionary phases: a stability phase below 350 °C, where volatile dispersion occurs, and a rapid increase phase above 350 °C, marked by significant microstructural changes from micro-fractures to extensive through-going fractures due to intense thermal decomposition. This decomposition leads to increased gas production and enhanced thermal fracturing. The threshold temperature is identified at 400 °C, above which the oil shale's mechanical strength and pore pressure increase, leading to decreased volumetric compression until stabilization. These findings demonstrate that higher temperatures enhance fracture connectivity and steam flow, optimizing the heating efficiency in oil shale extraction.

Changes in the porosity and permeability of oil shale under the overburden pressure often have a significant impact on the subsequent development of reservoirs. The authors of this article investigated the over burden porosity and permeability characteristics of tight oil reservoirs in two regions in China: the Fushun West Open-pit Mine in Liaoning and the Jimsar shale oilfield in Xinjiang. Overburden porosity and permeability experiments were conducted on oil shale cores. Three-dimensional visualization and quantitative analysis of the micropore structure of cores under different effective stresses were used to model the relationship between oil shale porosity, permeability, and effective stress. In addition, the stress sensitivity of oil shale reservoirs was analyzed, using the damage rates of permeability and stress sensitivity coefficients. The results indicated that in both regions, oil shale porosity and permeability exhibited a decreasing trend with increasing effective stress, following a negative exponential function. When the effective stress was less than 8 MPa, the permeability stress sensitivity coefficient decreased sharply. Once the effective stress exceeded 8 MPa, the stress sensitivity of permeability in both regions weakened, maintaining a range between 0.2 and 0.4 MPaâ1. The results of three-dimensional visualization simulations were the same as the experimental results. Taken together, the results showed that the porosity of different-sized pores decreased with increased stress, which reflected the synergistic effect of different-sized pores on porosity in shale. This study has practical significance for revealing the variation in pore size in shale reservoirs and establishing the physical characteristics of oil shale reservoirs.

This research delves into the geochemical aspects, non-isothermal thermogravimetric analysis, and model-free kinetics of oil shale samples from the Ãeltek region in Amasya, Türkiye. Shifting the focus to the core of the research, thermal and mass spectrometric analysis (TGâDTGâMS) experiments were conducted in an air atmosphere, employing three distinct heating rates of 10, 20, and 30 °C/min. The outcomes revealed two successive reaction stages: the breakdown of organic matter and mineral decomposition. In the breakdown stage, activation energy values exhibited a range of 160â163 kJ/mol, while in the mineral decomposition stage, the values varied between 208â214 kJ/mol, using model-free kinetic models.

Abstract:Organic matter is abundant in the shales and marls of the Pabdeh Formation in the southwestern Iran . They can be considered as a conventional or unconventional petroleum system in the region. This study evaluates the hydrocarbon generating potential and the feasibility of unconventional hydrocarbon resources of this formation from the viewpoint of petroleum geochemistry in the vast areas of southwest Iran . For this purpose, the results of Rock-Eval and vitrinite reflectance of the Pabdeh Formation from 43 oil fields in North Dezful Embayment, South Dezful Embayment, Abadan Plain, and northwestern Persian Gulf have been used. Geochemical parameters indicate that Pabdeh has good quantity and quality of organic matter in the region. However, it has not reached the maturity required for hydrocarbon generation in most areas. From the perspective of unconventional hydrocarbon resources, some layers of the Pabdeh Formation in the Dezful Embayment, especially in central areas, have the potential for oil shales. The shale oil potential is not suitable due to the low maturity and hydrocarbon saturation index of the Pabdeh Formation in the study area.Keywords: Pabdeh Formation, hydrocarbon generating potential, oil shale, shale oil IntroductionThe Zagros sedimentary basin hosts a significant amount of the world’s oil and gas reserves. This high amount of hydrocarbon results from several active petroleum systems in this basin over geological time. The Pabdeh Formation in some regions of southwest Iran contains a good quantity and quality of organic matters that, can act as either a conventional or unconventional petroleum system under suitable thermal conditions. This study aims to assess the hydrocarbon generation potential and the feasibility of unconventional hydrocarbon resources of this formation across the vast areas of southwest Iran from the viewpoint of petroleum geochemistry. For this purpose, Rock-Eval and vitrinite reflectance results of the Pabdeh Formation in southwest Iran from 43 fields, covering 353 kilometers in width and 596 kilometers in length, have been used.Materials & MethodsIn order to evaluate the hydrocarbon generation potential and the feasibility of the associated conventional and unconventional resources of the Pabdeh Formation on a regional scale, the Rock-Eval pyrolysis and vitrinite reflectance results of 641 samples within 43 fields across the Dezful Embayment, Abadan Plain, and northwest of the Persian Gulf were applied. Contamination can significantly impact the Rock-Eval pyrolysis results. In this research, the reliability and absence of contamination were assured before using the Rock-Eval data. For this purpose, samples with S1/TOC ratios greater than 1.5 and production indexes higher than 0.5 were excluded from the study. All Rock-Eval pyrolysis and vitrinite reflectance information were uploaded, analyzed, and interpreted using the geochemical software p: IGI 3.5.1.Discussion of Results & ConclusionThe Total Organic Carbon (TOC) levels in the studied samples vary from 0.09 to 1.6 wt%. Approximately 70% of the samples have a TOC greater than one, indicating that the Pabdeh Formation can quantitatively be considered a good source rock in the southwest of Iran. The highest organic matter content is found in the center of the Dezful Embayment. The Petroleum Potential Index is the sum of free hydrocarbons and those generated during the pyrolysis process. Samples from the Dezful Embayment exhibit the highest potential, while those from the northwest of the Persian Gulf show the lowest. Samples with good and very good potential contain Type II kerogen. The highest quality of organic matter in the Pabdeh Formation pertains to the central part of the Dezful Embayment.Vitrinite reflectance is one of the standard and efficient methods for evaluating organic matter maturity. The vitrinite reflectance values of the studied samples vary between 0.2 and 1. Most samples have values less than 0.6 or close to it, indicating immature to the early stages of the oil window. Moreover, other maturity parameters such as Tmax and Production Index confirm this result. Therefore, although the quantity and quality of organic matter in the Pabdeh Formation in southwest Iran are very good, the low maturity limits its contribution to hydrocarbon generation in the region. It should be noted that the samples were taken from the anticlines. It is therefore likely that this source rock could have matured in synclines and depressions and produced some hydrocarbons.Growing demand for energy, coupled with depleting conventional hydrocarbon reserves, has focused attention on unconventional hydrocarbon resources.. Oil shales are sedimentary rocks containing significant amounts of organic matter that have yet to reach the maturity stage necessary for hydrocarbon production. The TOC in oil shales ranges between 3 and 30 wt%. (Hosseiny & Mohseni 2023). It is evident that the greater the quantity and quality of organic matter in the oil shale, the greater and more economically viable the recoverable oil will be. Oil shales are rocks rich in organic substances with vitrinite reflectance below 0.6% and Tmax lower than 435 C° (Hinrichs et al. 2010). Accordingly, the strata of the Pabdeh Formation in the Dezful Embayment have the potential to be an oil shale resource especially in the central parts where the Aghajari, Rameshir, Gachsaran, and RageSefid fields are located. It should be noted that, , in addition to geochemical characteristics, the depth and thickness of the shale layer, mineralogical and petrological characteristics, geology, energy requirements and costs as well as current technology, are incredibly important in assessing the feasibility and capability of oil shales.Shale oils are liquid hydrocarbons in a free, soluble, or adsorbed state in marls or shales within the oil window. In other words, shale oils are petroleum resources found in source rocks that have not migrated or have migrated just a short distance from the source rock (Jiang et al. 2016). The quantity of organic matter plays a fundamental role in shale production potential and storage capacity. The minimum TOC to form a shale oil is two wt%. Since Type III kerogen is mainly associated with gas generation, source rocks containing this kerogen type have a lower potential for shale oil resources. In shale oils, the source rock must be situated within the oil window (Ro = 0.6%-1.2%) (Jiang et al. 2016). The first step in determining the sweet spots for shale oils is identifying the source rocks within the oil-generating window (Jarvie 2012). Determining the source rock's oil saturation is also highly important alongside maturity assessment. The amount of free hydrocarbons in the “S1” peak of Rock-Eval directly reflects the hydrocarbon saturation in the source rock (Jarvie 2012). The source rock's Oil Saturation Index (OSI) is obtained through the formula OSI=S1*100/TOC. Layers with an OSI greater than 100 mg HC/g TOC are considered to have productive potential (Jarvie 2012). The Pabdeh Formation has appropriate conditions for shale oil resources regarding the quantity and quality of organic materials in the Dezful embayment, especially in central areas. However, the maturity level in these areas is not sufficient. In the northern parts of the Dezful embayment, the Pabdeh could be within the oil window. However, samples from these areas show TOC and OSI less than two percent and 100 mg HC/g TOC, respectively.

Purposes In the process of in-situ steam-assisted oil shale extraction, the shear strength of oil shale plays a crucial role in the stability of injection and production wells as well as the mining gallery. Additionally, the shear strength of rock formation is influenced by temperature. The variations in the shear characteristics of oil shale under different temperatures and shear angles are investigated. Methods A steam generation apparatus was employed to heat the oil shale. In the experimental setup, steam temperatures were set at 100, 200, 300, 400, and 500 ℃, separately. Subsequently, the steam-treated oil shale was subjected to variable-angle shear experiments at shear angles of 45°, 55°, and 65°. According to the experiment results, the variable-angle shear parameters and peak shear strain of the oil shale were calculated. Furthermore, an analysis of the shear failure characteristics of the oil shale following exposure to different steam conditions was conducted. Findings The research findings can be summarized as follows: 1) At steam temperatures below 300 ℃, oil shale exhibits pronounced brittle failure characteristics, while at temperatures of 400 ℃ and 500 ℃, ductile failure characteristics becomes more evident; 2) The cohesion of oil shale first increases and then decreases with the increase of steam temperature. Similarly, the internal friction angle decreases initially with rising steam temperature, followed by an increase. The shear strength decreases as the shear angle increases; 3) The peak shear strain of the oil shale increases with steam temperature rising, and high shear angle has a significant impact on the peak shear strain of the rock; 4) The shear failure mode of the oil shale transitions from penetrating failure to combined failure with an increase in steam temperature, along with an increase in secondary cracks.

Purposes In the in-situ mining of oil shale, poor heat transfer efficiency and pronounced anisotropic differences present challenges. Methods In this study, standard samples from Xinjiang's Barikun oil shale are adopted to explore heat transfer variations in horizontal and vertical bedding at different temperatures through indoor experiments, and in-situ mining simulation was conducted. Findings The experimental results show that: 1) With the increase of temperature, the heat conduction coefficient of each bedding direction shows a "decreasing" trend, but the heat conduction coefficient of parallel bedding direction is greater than that of vertical bedding direction; 2) With the increase of temperature, the specific heat capacity first increases and then decreases. When the temperature is 400 ℃, the specific heat capacity is the maximum; 3) Combined with the micro-CT image, with the increase of temperature, the influence of increasing cracks on the heat conduction in the vertical bedding direction is greater than that in the parallel bedding direction. On the basis of the above experimental parameters, the "heat-solid" coupling model of in-situ electric heating of oil shale reservoir is established by COMSOL software. The simulation results show that: With the increase of heating time, anisotropic heat transfer difference gradually appears. When heating duration reaches 600 d, the heat transfer area in parallel bedding direction is obviously larger than that in vertical bedding direction, showing an "ellipse" shape. When heating duration reaches 1 440 d, the heat transfer area increases slightly, and the pyrolysis of the shale in the heating well control area is basically completed.

Abstract The Pabdeh Formation represents organic matter enrichment in some oil fields, which can be considered a source rock. This study is based on the Rock–Eval, Iatroscan, and electron microscopy imaging results before and after heating the samples. We discovered this immature shale that undergoes burial and diagenesis, in which organic matter is converted into hydrocarbons. Primary migration is the process that transports hydrocarbons in the source rock. We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion. Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons, but as catagenesis progressed, the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increased the pressure, leading to the development of damage zones in the source rock. The Pabdeh Formation’s small porethroats hindered effective expulsion, causing an increase in pore fluid pressure inside the initial microfractures. The stress accumulated due to hydrocarbon production, reaching the rock’s fracture strength, further contributed to damage zone development. During the expansion process, microfractures preferentially grew in low-strength pathways such as lithology changes, laminae boundaries, and pre-existing microfractures. When the porous pressure created by each kerogen overlapped, individual microfractures interconnected, forming a network of microfractures within the source rock. This research sheds light on the complex interplay between temperature, hydrocarbon generation, and the development of expulsion fractures in the Pabdeh Formation, providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.

Sub-critical water is an environment-friendly solvent. It is widely used for the extraction of various organic compounds. It can be used to dissolve and transport organic matter in oil shale. In this study, the conversion of oil shale was synergistically catalyzed by the addition of Fe or Ni to the Fe inherent in samples under sub-critical water conditions. Oil shale can be converted to gas, oil and residues of oil. Thermogravimetric (TG) analysis results presented that the weight loss of raw oil shale was up to 15.85%. After sub-critical water extraction, the weight loss rate of the residues was reduced to 8.41%. With the application of a metal catalyst, Fe or Ni, the weight loss of residues was further reduced to 7.43% and 6.57%, respectively. According to DTG curves, it was found that there were two weight-loss rate peaks. The decomposition process of kerogen in oil shale could be divided into two cracking processes. One is decomposed at a high velocity at around 420 °C, and another is decomposed at a low velocity at around 515 °C. Gas chromatography (GC) results of gas products indicated that Fe or Ni could contribute to producing normal alkanes, such as methane, ethane, propane, etc., which are produced by the hydrogenation of alkenes via hydrogen transfer during the conversion process of kerogen. Gas chromatography-mass spectrometry (GC–MS) was conducted to analyze the components of the liquid products. The results showed that n-alkanes, iso-alkane, oxygenated hydrocarbons and aromatic compounds were the major components of the kerogen cracking products. When Ni was introduced as a catalyst, the contents of aromatic compounds and oxygenated hydrocarbons in the liquid products were increased from 19.55% and 6.87% to 22.38% and 13.77%, respectively. This is due to the synergistic effect of the addition of Ni with the inherent Fe in oil shale under sub-critical water which ensures kerogen is more easily cracked to produce aromatic compounds and oxygenated hydrocarbons. [ABSTRACT FROM AUTHOR]

Oil shale, as a vast potential resource, is considered an important alternative energy source, and its effective development and economic utilization are of significant importance in alleviating the contradiction between energy supply and demand. Presently, the in situ conversion technology for oil shale has gained significant global attention, with numerous extraction methods undergoing active research and development. One of these methods is the in situ conversion of oil shale based on the hydration reaction of calcium-oxide-based composite material (CaO-CM). This approach harnesses the heat produced by the reaction between CaO-CM and water as a heat source for the pyrolysis of oil shale. This paper conducted experiments to assess the feasibility of temperature associated with this method. The feasibility study mainly includes two aspects: First, it is necessary to investigate whether the temperature generated by the hydration reaction of CaO-CM can meet the temperature requirements for the pyrolysis of oil shale. Through pyrolysis experiments of Xinjiang oil shale, the minimum temperature required for oil shale pyrolysis was determined to be 330 °C. High-temperature and high-pressure reaction vessels were employed to explore the temperature generated by the hydration reaction of CaO-CM. The results show that with the increase in environment pressure, environment temperature, and reaction mass, the maximum temperature generated by the hydration reaction of CaO-CM also increases (reach 455.5 °C), meeting the temperature requirements for the pyrolysis of oil shale. Second, the study evaluates whether the hydration reaction of CaO-CM can induce pyrolysis hydrocarbons of the oil shale. Through the pyrolysis experiments of oil shale based on the hydration reaction of CaO-CM, the changes in the content of pyrolysis hydrocarbons (S2) in oil shale before and after pyrolysis are measured. The results show that under 10 MPa pressure, the content of pyrolysis hydrocarbons in the oil shale decreased from 40.96 mg/g to 0.08 mg/g after pyrolysis. This confirms the feasibility of the temperature conditions for the in situ conversion of oil shale based on the hydration reaction of CaO-CM. [ABSTRACT FROM AUTHOR]

Oil shale is a potential strategic resource with large reserves and widespread application potential, and in situ combustion is an effective method to exploit oil shale. However, the interaction mechanism between pyrolysis and combustion reaction is still not clear; hence, the evolution of components and temperature in the reservoir is hard to describe, limiting the application of in situ combustion in oil shale. In this paper, we established a comprehensive reactive flow model to describe the in situ combustion in oil shale, and the in situ combustion process is analyzed in detail. During the in situ combustion, only pyrolysis reactions occur in the matrix system, while combustion reactions only occur in the fracture system. Under the interaction mechanisms of these two kinds of chemical reactions, in situ combustion upgrading can be carried out continuously. The produced oil and hydrocarbon gas per unit volume of oil shale are 0.06 m3/m3 and 12.5 m3/m3 , respectively, but about 83.3 m3/m3 of CO2 is produced that needs to be stored subsequently when air is directly injected into the reservoir to maintain the combustion reactions. Increasing oil content and air injection rate can increase the cumulative oil and gas production, but there are optimal values above which the increase rate slows down. The energy conversion efficiency of in situ combustion is 49.5, and it is much higher than the energy conversion efficiency in other in situ upgrading methods for oil shale. [ABSTRACT FROM AUTHOR]

As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in reducing national energy demand. In-situ catalytic technology, characterized by its high efficiency, low pollution, and minimal energy consumption, represents a key direction for future oil shale development. This paper provides a comprehensive review of research progress in in-situ oil shale mining technology, oil shale pyrolysis catalysts, the pyrolysis mechanism of kerogen, and the compatibility of different heating processes and catalysts. Furthermore, the paper proposes future research directions and prospects for oil shale in-situ catalytic technology, including reservoir modification, highefficiency catalyst synthesis, injection processes, and high-efficiency heating technology. These insights serve as valuable technical references for the advancement of oil shale in-situ catalytic technology. [ABSTRACT FROM AUTHOR]

The atomic structure and chemical behavior of heterocyclic fragments, such as pyridine, thiophene, and furan, in oil shale are crucial for optimizing its thermal pyrolysis process. This study employs density functional theory (DFT) to investigate the atomic structure and reactivity of typical heterocyclic fragments with impurities such as sulfur, nitrogen, and oxygen in kerogen macromolecules—the main organic compound of oil shale. By analyzing the free energy barriers, reaction rates and half-lives, we found that oxygen-containing heterocyclic compounds exhibited higher pyrolysis efficiency compared to nitrogen- and sulfur-containing heterocyclic compounds at the same temperature. We also analyzed the electrostatic potential and natural population analysis charges of the heterocyclic compounds and discovered that nitrogen- and sulfur-containing heterocycles had negative electrostatic potentials, making them more susceptible to electrophilic reactions. These findings provide valuable insights into the mechanisms and kinetics of various processes involved in oil shale processing, which can inform the development of more efficient and sustainable oil shale utilization strategies. [ABSTRACT FROM AUTHOR]

The composition of the products of cracking of oil shale (OS) from the Kashpirskoe deposit and kerogen isolated from it has been studied. The influence of OS mineral components on the material balance and qualitative composition of cracking products was shown. It was found that the amount of gaseous and solid products in kerogen cracking products decreased, and the yield of liquid products increased. The removal of mineral components from OS led to an increase in the oil content and a decrease in asphaltenes in liquid cracking products; the resin content changed slightly, and the yield of light fractions increased. The effects of mineral components on the structural-group characteristics of resins and asphaltenes in liquid cracking products were determined. The absence of mineral components led to an enlargement of resin molecules; on the contrary, asphaltene molecules became more compact. [ABSTRACT FROM AUTHOR]

This research delves into the geochemical aspects, non-isothermal thermogravimetric analysis, and model-free kinetics of oil shale samples from the Çeltek region in Amasya, Türkiye. Shifting the focus to the core of the research, thermal and mass spectrometric analysis (TG-DTG-MS) experiments were conducted in an air atmosphere, employing three distinct heating rates of 10, 20, and 30 °C/min. The outcomes revealed two successive reaction stages: the breakdown of organic matter and mineral decomposition. In the breakdown stage, activation energy values exhibited a range of 160-163 kJ/mol, while in the mineral decomposition stage, the values varied between 208-214 kJ/mol, using model-free kinetic models. [ABSTRACT FROM AUTHOR]

The Pabdeh Formation represents organic matter enrichment in some oil fields, which can be considered a source rock. This study is based on the Rock–Eval, Iatroscan, and electron microscopy imaging results before and after heating the samples. We discovered this immature shale that undergoes burial and diagenesis, in which organic matter is converted into hydrocarbons. Primary migration is the process that transports hydrocarbons in the source rock. We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion. Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons, but as catagenesis progressed, the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increased the pressure, leading to the development of damage zones in the source rock. The Pabdeh Formation's small porethroats hindered effective expulsion, causing an increase in pore fluid pressure inside the initial microfractures. The stress accumulated due to hydrocarbon production, reaching the rock's fracture strength, further contributed to damage zone development. During the expansion process, microfractures preferentially grew in low-strength pathways such as lithology changes, laminae boundaries, and pre-existing microfractures. When the porous pressure created by each kerogen overlapped, individual microfractures interconnected, forming a network of microfractures within the source rock. This research sheds light on the complex interplay between temperature, hydrocarbon generation, and the development of expulsion fractures in the Pabdeh Formation, providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings. [ABSTRACT FROM AUTHOR]

Downhole heaters are critical for effectively achieving in situ oil shale cracking. In this study, we simulate the heat transfer performance of a large-scale helical baffle downhole heater under various operational conditions. The findings indicate that at 160 m3/h and 6 kW the outlet temperature can reach 280 °C. Controlling heating power or increasing the injected gas flow effectively mitigates heat accumulation on the heating rod's surface. The outlet temperature curve exhibits two phases. Simultaneously, a balance in energy exchange between the injected gas and heating power occurs, mitigating high-temperature hotspots. Consequently, the outlet temperature cannot attain the theoretical maximum temperature, referred to as the actual maximum temperature. Employing h / ∆ p 1 3 as the indicator to evaluate heat transfer performance, optimal performance occurs at 100 m3/h. Heat transfer performance at 200 m3/h is significantly impacted by heating power, with the former being approximately 6% superior to the latter. Additionally, heat transfer performance is most stable below 160 m3/h. The gas heating process is categorized into three stages based on temperature distribution characteristics within the heater: rapid warming, stable warming, and excessive heating. The simulation findings suggest that the large-size heater can inject a higher flow rate of heat-carrying gas into the subsurface, enabling efficient oil shale in situ cracking. [ABSTRACT FROM AUTHOR]

The co-pyrolysis of biomass and fossil fuels has been the subject of studies on sustainable energy. Co-feeding oil shale with woody biomass can contribute to a transition into carbon neutrality. The present study analysed the thermal decomposition behaviour of oil shale and biomass blends (0:1, 3:7, 1:1, 7:3, 9:1, and 1:0) through thermogravimetric analysis (TGA) at 80–630 °C with a heating rate of 10 °C/min in CO2 and N2 atmospheres. A comparison of theoretical and experimental residual mass yields of oil shale–biomass mixtures indicated no significant interactions between the fuels. The blends contributed to a decrease of up to 34.4 wt% in solid residues compared to individual pyrolysis of oil shale, and the TGA curves were shifted from up to 10 °C to a lower temperature when the biomass ratio increased. The use of a CO2 atmosphere resulted in the production of solid residues, comparable to the one obtained with the N2 atmosphere. CO2 atmosphere can be used in oil shale–biomass co-pyrolysis, without affecting the decomposition process or increasing the yield of residues. A kinetic model method is proposed based on TGA data at 10, 20, and 30 °C/min. The apparent activation energies for a temperature range of 200–520 °C were in the order of 139, 155, 164, 197, 154, and 167 kJ/mol for oil shale–biomass 0:1, 3:7, 1:1, 7:3, 9:1, and 1:0 blends, respectively. From the isoconversional kinetic analysis, a two-stage pyrolysis was observed, which separated biomass and oil shale pyrolysis. A simulation of biomass and oil shale co-pyrolysis was conducted in Aspen Plus® using TGA-derived kinetic data. The model prediction resulted in a close match with the experimental thermogravimetric data with absolute errors from 1.75 to 3.78%, which highlights the relevance of TGA analysis in simulating co-pyrolysis processes. [ABSTRACT FROM AUTHOR]

Oil shale, as an unconventional energy source, has attracted much attention in countries worldwide. The traditional way of extracting oil shale from the open pit is not only costly but also polluting to the environment. Sufficient understanding of the relationship between subsurface fractures and temperature fields is important for the extraction of oil shale and is of great significance for the actual in-situ extraction of oil shale. The study of fracture initiation and expansion in oil shale formations is based on the effect of fractures on convective heating efficiency in oil shale in situ conversion technology. In view of the objective situation that hydraulic fracturing can enhance the rate of the permeability and heating efficiency of oil shale formations, and hence the oil yield, the effect of single fractures with different fracture heights (2 mm, 4 mm, 8 mm) on the temperature field of oil shale; and the effect of multiple fractures (two, three and four fractures) on the temperature field of oil shale are investigated under convective heating methods. [ABSTRACT FROM AUTHOR]