The autothermic pyrolysis in-situ conversion process of oil shale has emerged as a vital development direction due to its advantages of environmental friendliness and low cost. However, previous studies predominantly employed constant injection and production parameters, which often result in inefficient compression energy injection and formation oxidation losses, thereby limiting further improvements in energy efficiency and oil production. To address these issues, this study establishes a dynamic optimization model for injection-production parameters in the autothermic pyrolysis in-situ conversion process of oil shale, developing a dynamic control methodology for gas injection rate and oxygen content to enhance the economic viability and feasibility of the process. The results indicate that under the optimal combination of gas injection – adjustment time, decay rate, and terminal flow rate – the steady-state phase during late production can significantly reduce input compression energy and inhibit hydrocarbon oxidation losses, ultimately leading to a substantial increase in the peak energy efficiency and cumulative oil production. Furthermore, by synergistically regulating oxygen content and injection rate during the early production stage, the compression energy can be further reduced, ultimately elevating the energy efficiency to approximately fourteen, demonstrating the technical feasibility for industrial-scale production. These findings and the identified key parameters provide crucial theoretical and technical support for the large-scale application of the autothermic pyrolysis in-situ conversion technology for oil shale.

Against the backdrop of global low-carbon energy transition, the green, economical, and efficient development of shale oil and gas resources faces a series of challenges in theoretical frameworks, technological costs, low-carbon innovation, and engineering management. To foster technological independence and advance low-carbon development through academic exchange, the 6^th International Symposium on Shale Oil and Gas Exploration, Development, and Utilization Technology was held by Jilin University in Changchun, China, from November 7 to 9, 2025. This symposium gathered over 270 experts and scholars from more than 50 institutions worldwide featuring 61 presentations spanning geological theory, intelligent exploration, drilling and completion technologies, in-situ conversion, pyrolysis mechanisms, enhanced recovery, and low-carbon strategies. The discussions underscored a decisive shift towards intelligent, integrated, and green technological solutions, highlighting the critical role of artificial intelligence, nanotechnology, and carbon management in field advancement. This event significantly strengthened the industry-academia-research-application collaboration system, providing important momentum for achieving technological independence and driving the shale industry towards a sustainable and secure energy future.

The autothermic pyrolysis in-situ conversion process for oil shale (ATS) offers the advantages of low development costs and the capability to exploit deep oil shale resources. However, oil shale formations with low oil content encounter the challenge of insufficient heat-generating donors in the thermal cracking residue, making it difficult to sustain the autogenous thermal reaction through oxidative exotherm. In this study, we propose a natural gas-assisted autogenous thermal in-situ conversion technology (H-ATS) designed to develop low oil content shale, and we analyze its mechanism through numerical simulation across oil shales with varying oil contents. The results show that introducing 2.0% natural gas into the injected air successfully triggers the autogenous thermal reaction in low-oil-content shale, achieving an energy efficiency of 3.70. For medium oil content shale, a 2.0% natural gas addition, and for high oil content shale, a 4.0% addition, significantly reduces the gas compression energy required, enhancing energy efficiency to 8.11 and 13.04, respectively—representing improvements of 29.47% and 19.19% over the ATS process alone. This study evaluates the applicability of H-ATS technology across various oil shale formations, providing a new approach for the commercialization of in-situ conversion technology.

Organic-rich shale is a significant potential source of oil and gas that requires development through in situ conversion technology. However, the evolution patterns of the internal three-dimensional (3D) pore structure and kerogen distribution at high temperatures are not well understood, making it difficult to microscopically explain the evolution of the flow conductivity in organic-rich shale at high temperatures. This study utilizes high-resolution X-ray computed tomography (micro-nano CT) to obtain the distribution of pores, kerogen, and inorganic matter at different temperatures. Combined with the pyrolysis results for the rock, the evolution of the pore structure at various temperatures is quantitatively analyzed. Based on three-phase segmentation technology, a model of kerogen distribution in organic-rich shale is established by dividing the kerogen into clustered kerogen and dispersed kerogen stored in the inorganic matter and the pores into inorganic pores and organic pores within the kerogen skeleton.

The results show that the inorganic pores in organic-rich shale evolve through three stages as the temperature increases: kerogen pyrolysis (200–400 ℃), clay mineral decomposition (400–600 ℃), and carbonate mineral decomposition (600–800 ℃). The inorganic pores porosity sequentially increases from 3% to 11.4%, 13.1%, and 15.4%, and the roughness and connectivity of the inorganic pores gradually increase during this process. When the pyrolysis temperature reaches 400 ℃, the volume of clustered kerogen decreases from 25% to 12.5%. During this process, the relative density of kerogen decreases from 9.5 g/cm³ in its original state to 5.4 g/cm³, while the kerogen skeleton density increases from 1.15 g/cm³ in its original state to 1.54 g/cm³. Correspondingly, 7%–8% of organic pores develop within the clustered kerogen, accounting for approximately 50% of the volume of clustered kerogen. In addition, approximately 30% of the kerogen in organic-rich shale exists in the form of dispersed kerogen within inorganic matter, and its variation trend is similar to that of clustered kerogen, rapidly decreasing from 200 to 400 ℃ and stabilizing above 400 ℃. The results of this study provide an essential microscopic theoretical basis for the industrial development of organic-rich shale resources.

In-situ conversion is essential for the development of oil shale resources. Reservoir blockage has been confirmed to be a technological bottleneck via laboratory-scale experiments and field tests. This issue arises from the precipitated asphaltene and its thickening effect on the pyrolysis oil. Promoting in-situ secondary cracking of asphaltene has the potential to mitigate blockage. However, the secondary cracking characteristics of asphaltene have not yet been determined. In this study, asphaltenes were obtained under different pyrolysis temperatures, atmospheres and duration times, their secondary cracking mechanisms were investigated. These findings demonstrate considerable mass loss and discrepant reaction processes across different asphaltenes. Firstly, the mass loss of asphaltenes exceeds 80% at 500 ℃ for all the samples, and the released space can restore reservoir permeability. Second, based on the evolution of the activation energies and pyrolysis gas components, the asphaltenes obtained under severe conversion conditions undergo pyrolysis defined by synchronous two-stage reactions, whereas the asphaltenes obtained under mild conversion conditions undergo pyrolysis defined by sequential three-stage reactions. Finally, a method for eliminating reservoir blockage was proposed based on the above theories, involving inhibiting asphaltene migration and promoting its in-situ secondary cracking by controlling the parameters of the heat-carrying fluid, thereby achieving an unaffected reservoir or reservoir self-unblocking. The obtained results can provide valuable references for the in-situ exploitation of oil shale.

The coolant must be pre-stored in the sampler before the freezing procedure for natural gas hydrate sampling is applied. The coolant’s storage capacity throughout the sampler-lowering procedure is crucial to ensure successful sampling. In this study, the key factors influencing storage capacity were coolant density, dry ice specific surface area, ambient pressure, and temperature difference. An orthogonal method was used to analyze each factor’s level of influence and potential action processes. The results indicated that ambient pressure, specific surface area, coolant density, and temperature difference all had significant impact. Ambient pressure affects the phase-change path of dry ice, and high pressure increases the likelihood of dry ice melting, greatly reducing latent heat. The larger specific surface area could help to generate a compact dry ice layer to protect the interior, but it may cause cold energy loss during the freezing process. Dry ice, with a smaller specific surface area, may be a better option. Low-temperature alcohol can separate the dry ice layer from the surrounding environment, allowing for heat exchange. However, a low coolant density may promote heat exchange between the alcohol layer and surrounding environment, resulting in the loss of dry ice. The appropriate coolant formulation comprised of a mixture of 2.5 kg of granular dry ice and 1 L of alcohol, temperature difference maintained at 105 K, and the working pressure of 0.1 MPa.

Given the abundance of clay minerals in oil shales, the in-situ cracking of oil shale is preferably enhanced by catalysis, such as by modifying reservoir clays with soluble catalytically active materials. In this work, nickel-modified montmorillonite was synthesized via a simple method, and the feasibility of in-situ catalytic cracking of oil shales to facilitate engineering implementation was investigated. Thermogravimetric analysis was performed to assess the impact of the catalyst on the pyrolysis behavior of kerogen. The results demonstrated that nickel-modified montmorillonite effectively reduces the initial cracking temperature of kerogen and enhances the hydrocarbon generation rate. The results of thermogravimetric-Fourier transform infrared spectrum and thermogravimetric-mass spectrometry analysis revealed a significant boost in the production of smaller molecules and non-condensable gases, including hydrogen, methane, ethane, and benzene. Concurrently, there was a notable reduction in carbon dioxide and sulfur dioxide emissions. Pyrolysis experiments were conducted to provide additional evidence of the effectiveness of nickel-modified montmorillonite, confirmed by a decrease in semi-coke production and a notable 11.25% increase in oil yield. Furthermore, the composition analysis of shale oil indicated an increased production of alkenes and aromatic hydrocarbons. These findings suggest that the addition of nickel-modified montmorillonite effectively enhances the depolymerization, deoxygenation and aromatization reaction, resulting in the formation of valuable products during the pyrolysis of oil shale kerogen. This study offers a promising avenue of cost-effective and efficient in-situ oil shale exploitation.

In the face of the complex global energy transition, the development of unconventional oil and gas resources, such as oil shale, shale oil, and shale gas, encounters challenges related to carbon neutrality, technological complexities, and costs. However, the world's strained energy landscape and the fact that the new energy industry has yet to take shape also present rich opportunities for the development of these resources. Against this background, a conference platform was established at Jilin University for facilitating scholarly exchange and discussion on the exploration and development technologies of shale oil and gas. The 5^th International Symposium on Shale Oil and Gas Exploration and Development Technologies was successfully held in Changchun from November 10 to 12, 2023. The symposium attracted over 210 experts and scholars from more than 59 institutions worldwide, representing the field of shale oil and gas exploration, development, and utilization. Participating delegates shared their accomplishments in the realm of shale oil and gas exploration and development technologies, engaging in profound discussions and fruitful exchanges on these subjects.