China has achieved major breakthroughs in the exploration of deep coal-rock gas, marking a strategic shift from traditional shallow coalbed methane to deep coal-rock gas. As a high-quality source rock, coal-rock is characterized by high organic matter abundance, continuous gas generation throughout its entire evolution process, and strong storage capacity, which is conducive to the formation of coal-rock gas reservoir where adsorbed and free gases coexist. Based on the new theory of "whole petroleum system of coal measures", this paper reveals the accumulation mechanism and resource potential of coal-rock gas. The preliminary evaluations indicate that the deep coal-rock gas resources with a burial depth greater than 1 500 meters exceed 100×10 ¹²m ³ in China, approximately twice that of conventional natural gas resources, providing a resource foundation for the formation of super-large gas fields. In Daji block of Ordos Basin, large-scale development has been achieved through the application of horizontal well and volumetric fracturing technologies, with an average daily production of 12×10 ⁴m ³ per well and cumulative proven reserves of 1 452×10 ⁸m ³, demonstrating promising development prospects. At present, China has established a series of key technological systems, including experimental testing, optimized drilling and completion, fracturing stimulation, and volume development, which support the efficient extraction of coal-rock gas. However, challenges still exist in coal-rock gas development, such as incomplete theoretical system, unclear sedimentary evolution mechanisms, and insufficient research on accumulation mechanisms. To address these issues, it is suggested to systematically conduct nationwide resource assessments, strengthen exploration in key areas, optimize mining right management, and promote theoretical innovation and demonstration applications. These efforts will provide strategic support for increasing natural gas reserves and production and enhancing China’s energy self-sufficiency capacity.

The world today has entered a new era of superimposed development of the sixth scientific revolution, the fourth industrial revolution, and the third energy revolution. To address the new challenges of global climate change and the energy green and secure transformation, humanity will surely seize the new opportunities to break through the limitations of traditional single-energy replacement pattern and the barriers among energy systems, and accelerate the construction of a new paradigm of synergistic and intelligent multi-energy integration, characterized by a six-in-one model of coal, oil, natural gas, new energy, carbon neutrality and artificial intelligence. Energy science, grounded in the evolutionary processes of the Earth system, investigates the formation and distribution of various energy resources, regional evaluation, development and utilization, orderly substitution, and future prospects across temporal and spatial scales. From the perspective of building China as an energy powerhouse, and based on research on global green energy transition, climate change, carbon neutrality, China’s energy resource endowment and energy green and secure transition, this paper proposes the concept, theoretical framework, technical pathways, and development strategies of the Integrated Whole-Energy System (IWES). IWES refers to a safe, efficient, and intelligent mega-system in which aboveground and underground energy resources exhibit genetic continuity, ordered substitution, overlapping coexistence, and coordinated integration for utilization. The development philosophy of IWES advocates the establishment of a holistic energy system perspective and the construction of six subsystems, namely the Whole Petroleum System, the Whole Coal-rock System, the New Energy System, the Multi-Energy System, the Super Energy System, and the Carbon Cycle System. The strategic approach of IWES emphasizes clean coal with carbon emission reduction, stabilized oil with increased gas production, strengthened renewables with enhanced reserves, multi-energy integration, intelligent economy, and green and safe development. The technological priorities of IWES focus on nine critical areas, including coal cleaning, in-situ conversion of shale and coal resources, wind energy, solar energy, hydrogen energy, energy storage, geothermal energy, controllable nuclear fusion, and intelligent governance. The development pathway of IWES follows a three-step roadmap, namely to consolidate multi-energy complementarity during foundation and integration period, to break through core technologies during accelerated transformation period, and to establish an intelligent energy ecosystem during system maturity period. The significance of IWES lies in the potential to address the inherent contradictions of the fossil energy "impossible triangle", drive the building of a new energy system with new energy at its core,facilitate the achievement of carbon neutrality, empower the construction of an energy powerhouse, and contribute a "China Solution" to the global energy green transition and sustainable development of the Earth.

This study comparatively analyzes the key differences in the development of tight oil reservoirs between China and the rest of the world, with a particular focus on the mechanisms, technological advancements, and limitations of CO ₂ enhanced oil recovery (CO ₂-EOR). The research indicates that compared to typical reservoirs in North America, tight reservoirs in China are generally characterized by low pressure, high viscosity, strong heterogeneity, and developed micron-to-nanoscale pore systems, which face dual challenges of poor injectivity and low recovery efficiency during hydrocarbon development. Although CO ₂ injection can enhance permeability by mineral dissolution, the reaction byproducts, such as iron-bearing minerals, carbonates, and asphaltenes, are prone to plug pore throats, thereby affecting its practical application. At micro- and nano-scales, traditional methods such as the Peng-Robinson equation of state (PR-EOS) and Darcy’s law struggle to accurately capture the phase behavior and flow of multiphase fluids, which necessitates integrated approaches including nanochip experiments and fluid-solid coupling molecular simulations to deepen understandings of underlying mechanisms. CO ₂ flooding primarily targets tight oil in meso- and macropores where gas channeling remains a critical challenge. CO ₂ foam flooding can mitigate gas channeling, but it requires substantial amounts of surfactants for foam generation and stabilization. CO ₂ nano-bubbles, boasting high stability, effective gas-channeling control, and superior oil-displacement performance, are recognized as one of the most promising research directions for future CO ₂ flooding technologies. Additionally, further optimization of CO ₂-responsive plugging systems is required in terms of plugging strength, manufacturability, and injectability to enhance their adaptability and practical application efficacy in tight reservoirs.

In the context of the global energy transition and the "dual-carbon" targets, new energy systems enter into a phase of large-scale deployment and high-quality development. However, the collaborative development across technologies, systems, and spatial dimensions continues to face significant challenges. Focusing on the "four-green" new energy system, i.e., green electricity, green hydrogen, green storage, and green heat, this study proposes a four-dimensional evaluation framework encompassing the dimensions of technology, system, space, and institution. It systematically reviews improvements in wind-solar efficiency and changes in levelized cost of electricity, cost-lifetime characteristics of sodium-ion/flow batteries and long-duration energy storage, electrolyzer efficiency and green hydrogen integration demonstrations, as well as engineering progress in geothermal energy utilization, which were validated through authoritative data and case studies in recent years (2022 to 2025). The results indicate that onshore multi-megawatt and deep offshore wind power, tunnel oxide passivated contact (TOPCon) or heterojunction technology (HJT) solar cells, and tandem photovoltaics are rapidly entering mass production; sodium-ion/flow batteries and compressed air energy storage (CAES) tec hnologies complement each other across different time scales; proton exchange membrane (PEM) and solid oxide electrolysis cell (SOEC), coupled with green ammonia and green methanol, establish an integrated value chain; enhanced geothermal systems (EGS) demonstrate empirical improvements in injection-production efficiency and microseismic monitoring. Targeting the "Sustainable Triangle" encompassing "security-economy-cleanliness-resilience-synergy", the study proposes practical implementation pathways, including the coordination between capacity prices and ancillary services, the full-lifecycle certification for green hydrogen, the certification for geothermal injection-production and cycle, and synergistic management of land and water resources under the regulations of "three lines and one list" (red line for ecological protection, bottom line for environmental quality, upper line for resource utilization, and access list for ecological environment) and "four water-based principles" (planning land, city, industry, and population based on water resources). The study provides structured approaches and implementation proposals based on policy-engineering integration to facilitate value realization and replicable diffusion of new energy systems during China’s 14th and 15th Five-Year Plan periods. It argues that during the "14th Five-Year Plan" period (2021 to 2025), new energy development should prioritize exploration and technological breakthroughs, while proving technical feasibility through validation, deploying demonstration projects, and laying the institutional foundation. During the "15th Five-Year Plan" period (2026 to 2030), new energy will enter a stage of large-scale and high-quality development, achieving a synergistic integration of cost competitiveness, performance excellence, and certification compliance, thus facilitating the value realization, replication and dissemination of new energy systems. This will provide theoretical support and actionable institutional and engineering pathways for China to achieve a high-quality leap in new energy development while ensuring energy security.

Geothermal energy is a renewable, efficient, clean, and environmentally friendly resource that is highly valued worldwide. Based on the distribution and utilization status of geothermal resources both domestically and internationally, this paper reviews the distribution patterns of domestic and foreign geothermal resources, the current development technologies and utilization as well as the proven geothermal resource potential of China’s geothermal resources, and prospects for the future development of geothermal energy in China, which provides valuable insights for the geothermal energy exploitation and utilization. Global high-temperature geothermal resources are primarily distributed along divergent and convergent plate boundaries, whereas low- to medium-temperature geothermal resources are mainly found in sedimentary basins and orogenic belts within tectonic plates. China’s geothermal resources displays distinct regional characteristics and distribution patterns, with their formation and macro-distribution controlled by geological structure, as well as the Mediterranean-Himalayan and Circum-Pacific geothermal belts. Moreover, China is rich in geothermal resources, accounting for one-sixth of the global total. While China leads the world in the direct utilization of geothermal energy, it significantly lags behind in geothermal power generation. Overall, China has significant prospects for the development and utilization of geothermal resources, driven by resource endowment, market opportunities, and policy support. However, due to existing discrepancies in the national assessment of geothermal resources and the predominant focus on development and utilization of low- to medium-temperature geothermal resources in eastern regions, it is recommended to initiate a new round of nationwide geothermal resource evaluation to qualify the national reserves. Additionally, efforts should be made to enhance the exploration of high-temperature geothermal resources in eastern China, further elucidate the genetic mechanisms of high-temperature geothermal systems, and deepen research on target area optimization and development strategies.

The utilization and storage of CO ₂ in oil and gas production processes is a crucial component of CO ₂ capture, utilization, and storage (CCUS) technology, and represents a key strategic priority for China’s energy transition. China’s abundant unconventional oil and gas resources, including tight and shale reservoirs, present unprecedented opportunities for the CO ₂ utilization and storage technologies. This also provide a critical breakthrough for balancing energy security with carbon reduction. The paper systematically reviews the progress in fundamental research on CO ₂ utilization (including fracturing, enhanced oil recovery (EOR), enhanced gas recovery (EGR)) and storage in tight/shale oil and gas reservoirs over the past decade, enhancing the understanding of the underlying mechanisms. Based on a summary of field practices, the targeted future research directions are outlined as below:(1) CO ₂ fracturing can reduce breakdown pressure and increase fracture complexity; however, the mechanisms of CO ₂ storage remain incompletely understood. The primary challenges for CO ₂ fracturing and storage include increasing viscosity and carrying sand, controlling the formation and expansion of fracture networks, and process design. (2) CO ₂-EOR mainly relies on the CO ₂-water-crude oil-rock interactions and miscibility effect, and CO ₂ diffusion is critical for hydrocarbon recovery in tight matrix-fracture structure reservoirs. The storage mechanisms primarily encompass four types:structural trapping, capillary trapping, dissolution, and mineralization. Future research will focus on nanoconfined phase behavior, miscibility mechanisms, gas channeling control, and sweep control methods. (3) CO ₂-EGR can improve shale gas recovery through the main mechanisms involving competitive adsorption, pressure maintenance, and inhibition of water invasion. Simultaneously, CO ₂ storage is achieved through four mechanisms:dissociation, adsorption, dissolution, and mineralization. However, the mechanisms of multiphase interactions, complex phase behavior characteristics, and long-term evolution pattern during CO ₂ storage still require further exploration. Currently, the integrated design and multi-objective optimization methods for CCUS are not yet fully developed, and cannot provide precise guidance for field-scale applications. It is imperative to advance research on mass transfer mechanisms during near-miscible/miscible displacement and multiple-contact mass transfer, develop effective methods for controlling preferential pathways and sweep efficiency, and establish a quantitative evaluation and monitoring system for the long-term evolution of CO ₂ storage. These efforts are essential for effectively promoting the application of CCUS technologies in the exploitation of tight and shale oil and gas resources.

As the core equipment in oil and gas drilling, the technical performance of drill bits directly influences drilling efficiency and overall costs. By systematically reviewing the technological development of drill bits in both domestic and international contexts, this study clarifies the evolution from drag bits, roller cone bits, diamond bits, and composite bits to intelligent bits, thereby providing a fundamental basis and direction for drill bit design and development. The analyses indicate that technological innovation in drill bits is the essential driver for the continuous advancement of drilling technologies, while innavotive transformations in drill bit technology are in turn driven by increasingly complex drilling requirements. Advances in drill bit technology are primarily reflected in the following aspects:(1)Design methods have progressed from static to dynamic models, from single-factor to multi-factor considerations, and from experience-based approaches to digitalized methodologies; (2)The dominant drill bit types have shifted from roller cone bits to PDC bits, accompanied by a transition in product development from mass production of roller cone bits to customized design and manufacturing of PDC bits; (3)Tooth materials have evolved from ordinary carbon steel to high-performance cemented carbides and diamond-based superhard composites; (4)The tooth profile has evolved from planar cutter to novel shaped cutters; (5)Hydraulic structure technologies have developed from physical experimentation to refined computational fluid dynamics simulations; (6)Experimental evaluation techniques have evolved from basic bench testing to collaborative testing of drill bits and associated tools, and further to rock-breaking experiments that simulate in-situ conditions; (7)Manufacturing processes have transitioned from traditional mechanical machining to modern automated and intelligent manufacturing technologies. To address the drilling requirements of complex oil and gas reservoirs, such as deep and ultra-deep layers, future research on drill bits will focus on new methods, new structures, new materials, precise and personalized design, integrated scientific application, and intelligent technological innovation. These efforts aim to develop high-performance drill bits suitable for diverse drilling conditions, and support the critical demand for enhancing drilling speed and efficiency in complex oil and gas drilling operations.

To address the challenges in CO ₂ flooding and sequestration in Yangchang oilfield, including low-permeability reservoir with poor gas injection performance, difficulty in achieving miscibility under low formation pressure, and limited sweep efficiency in immiscible flooding, the study explores a new technical path for significantly enhanced oil recovery and high-efficiency carbon storage in low-permeability tight oil reservoirs. The paper systematically elaborates the integrated CO ₂ fracturing-flooding-storage technology in Yanchang oilfield and its field practice, and proposes a new theoretical understanding that expanding sweep volume, enhancing miscibility and imbibition constitute the main mechanisms of the integrated CO ₂ fracturing-flooding technology for enhanced oil recovery. Correspondingly, an enhanced oil recovery technology has been developed, focusing on CO ₂-induced fracture extension and reservoir stimulation, miscibility enhancement, improved imbibition oil displacement, and gas channeling control and prevention. Besides, this study reveals the dynamic evolution mechanism of CO ₂ storage in reservoirs,clarifies the long-term sealing mechanism of cap rocks, and establishes corresponding sealing performance evaluation methods. To further ensure CO ₂ storage safety, a full-space monitoring system for reservoirs has been constructed. Based on the above technology, oilfield tests demonstrate the cumulative incremental oil production of 2.6×10 ⁴ tons, safe and effective sequestration of 124 000 metric tonnes of CO ₂, and an estimated 12.1 % increase in enhanced oil recovery. Field practice in Yanchang oilfield shows that the integrated CO ₂ fracturing-flooding and storage technology has significant application potential in low-permeability tight oil reservoirs.

The profound complexity of contemporary global development landscape, combined with increasingly fragmented energy governance has heightened uncertainty regarding the energy transition and sustainable development of the oil and gas sector. Meanwhile, a new wave of technological and industrial transformation is gaining momentum worldwide. Digital empowerment and advances in intelligent technologies are creating new opportunities for the development and transition of the oil and gas industry and its enterprises. Through a systematic review of the current energy transition status and development trends in major economies and international oil companies, this study investigates the sustainable development strategies and implementation pathways for China’s oil and gas industry. The world is currently undergoing its third energy transition, characterized by a shift toward cleaner energy, technological advancements, electrification, and intelligent systems. Policy incentives and technological innovation have emerged as the primary factor driving this transition. However, challenges such as geopolitics, energy security, and the supply of critical mineral resources create a dynamic of "stability amidst change" in the transition of the oil and gas sector. Although China’s major oil and gas companies have made significant progress in renewable energy, energy storage, hydrogen, and carbon capture, utilization, and storage (CCUS), they continue to face the dual pressures of ensuring supply and reducing carbon emissions. In response, this paper advocates a sustainable development strategy for China’s oil and gas industry, focusing on the phased implementation, supply-side reforms, integration of digital and intelligent technologies, transformation of raw material structures, and orderly transition to clean substitutes. The insights gained from this study hold significant theoretical and practical implications for advancing China’s energy transition, reshaping the industrial landscape, and achieving high-quality, sustainable development.

The 10 000-meter ultra-deep well drilling and logging technologies are crucial for deep oil and gas exploration and serves as a key indicator of a nation’s strength in energy exploration and development. Through the implementation of ultra-deep well drilling projects exemplified by Well Shenditake 1, China has preliminarily established an ultra-well drilling and logging technology system with distinctive Chinese characteristics. Critical drilling technologies, such as 15 000-meter automated drilling rigs, Grade V150 high-strength drill pipes, and high-performance water-based drilling fluids resistant to 240 ℃ have been successfully developed, ensuring safe and efficient drilling operations. Logging tools,including a 230 ℃ and 180 MPa slim-hole imaging logging tool, a supporting ground acquisition and processing platform, and communication cables suitable for depths exceeding 10 000 meter,have been successfully developed, facilitating the acquisition of geological engineering data from 10 000-meter-deep formations. Despite the significant breakthroughs achieved in China’s 10 000-meter-deep drilling engineering technology, gaps persist relative to the top international standards. Key areas requiring further improvement include the long-term reliability of downhole tools and instruments, service life under high temperature and pressure conditions, long-range imaging accuracy, and advanced materials. Looking forward, 10 000-meter-deep well drilling and logging technology will continue to evolve toward greater depth, higher intelligence, greater efficiency, and enhanced safety. Key technological breakthroughs remain essential, particularly in materials with high temperature resistance exceeding 260 ℃, intelligent autonomous decision-making systems, high-efficiency rock-breaking tools, extreme high-temperature and high-pressure downhole imaging technologies, and intelligent quantitative interpretation systems. Through profound cross-disciplinary integration and ongoing iterative innovation, these advancements will provide robust technical support for the large-scale exploration and economically efficient development of deep oil and gas resources.

The success of "shale revolution" in North American has profoundly reshaped the global energy structure. A systematic analysis of the efficient development patterns of the Permian super unconventional hydrocarbon basin is of substantial strategic significance for promoting the large-scale, economically efficient development of China’s shale oil and gas resources and safeguarding national energy security. Drawing on full-chain big data from 100 000 wells in the Permian Basin, encompassing drilling, fracturing, production and cost, this study adopts a hybrid methodology integrating mathematical statistics, random forest machine learning, and NSGA-II multi-objective Pareto optimization algorithm to generate analytical visualizations through heat maps of development indicator influencing factors, lateral-to-vertical depth ratio charts, variations in EUR per kilometer of lateral length, and co-optimization plots of lateral length and proppant intensity. The results quantitatively reveal the intrinsic correlations and synergistic optimization pathways among the multi-dimensional parameters of "geology-engineering-economy" in shale oil and gas development. The results indicate that:the Permian Basin has undergone five developmental stages of conventional foundation, shale breakthrough, scale expansion, intelligent transformation, and mature optimization, forming an efficient development paradigm characterized by "extended lateral length, high-intensity fracturing, and data-driven decision-making", and achieving a fundamental shift from "production maximization" to "economic benefit maximization". The lateral length P50 increased from 1 451 m to 3 152 m, while the proppant intensity P50 rose from 1.6 t/m to 3.3 t/m. The development benefits of shale oil and gas is jointly controlled by resource endowment and engineering technology, exhibiting a pattern of diminishing marginal returns. The single-well EUR peaked at 12.83×10 ⁴t in 2020 and declined to 8.56×10 ⁴t in 2024, while the EUR per kilometer of lateral length decreased from 4.60×10 ⁴t/km to 2.71×10 ⁴t/km, indicating that shale gas exploitation enters the economic-returns-driven phase. The optimal proppant intensity increases monotonically with burial depth and lateral length. For deep reservoirs (3 500-4 000 m) with long horizontal intervals (4 500-5 000 m), the proppant intensity should be increased to 3.5 t/m to achieve optimal economic performance targets, with EUR≥11.4×10 ⁴t and oil-equivalent production per unit drilling and completion cost≥100 t/10 000 USD. Considering the geological characteristics of China’s shale oil and gas reservoirs, such as large vertical span and complex resource endowments, four core development insights are derived:promoting geology-engineering integration to achieve precise matching between reservoir properties and engineering parameters; strengthening the dynamic optimization of fracturing parameters for moderately high proppant intensity and implementing differentiated design; establishing a data-driven decision-making system and developing localized optimization charts; formulating classified and graded development strategies with forward-looking deployment of replacement resource areas. The findings provide a replicable quantitative paradigm and practical pathway for the economically efficient development of China’s shale oil and gas resources.

The efficient development of coalbed methane (CBM) plays a strategically important role in ensuring national energy security and promoting energy structure transformation. Based on the new situation and recent progress in CBM exploration and development during the 14th Five-Year Plan period (2021-2025), and considering the methodological innovations in resource evaluation under the context of breakthroughs in deep CBM exploration, this study systematically summarizes the evaluation results of CBM resources shallower than 5 000 m within the petroleum concession areas of China National Petroleum Corporation (CNPC), and proposes future development trends for the CBM industry. The evaluation results show that the total amount of CBM resources shallower than 3 000 m nationwide is 39.88×10 ¹²m ³, with technically recoverable resources of 16.61×10 ¹²m ³, representing a 43 % increase compared with the 13th Five-Year Plan period (2016-2020). Within CNPC’s concession areas, the geological CBM resources shallower than 3 000 m and 5 000 m are 22.58×10 ¹²m ³ and 36.82×10 ¹²m ³, respectively, including 14.24×10 ¹²m ³ of CBM resources at depths between 3 000 m and 5 000 m. The most abundant resources are found in Carboniferous-Permian, medium- to high-rank coals buried bewteen 2 000 m and 4 000 m. Assuming a benchmark gas price of 1.5 CNY/m ³, the economically recoverable CBM resources shallower than 3 000 m and 5 000 m are 8.04×10 ¹²m ³ and 12.57×10 ¹²m ³, respectively. These evaluation results have been directly applied to guide well deployment in the deep CBM pilot test area of the Ordos Basin and to optimize risk wells targeting multiple thin coal seams in southern China, forming a replicable breakthrough model for deep CBM exploration. The Ordos and Qinshui basins will continue to lead CBM production growth, while the multi-thin seam CBM in southern China and medium- to low-rank CBM in northwestern and northeastern China possess enormous resource potential, representing key directions for future reserve expansion.

Deep coalbed methane (CBM)reservoirs have become an important growth driver for China’s natural gas production. Field practices have revealed that fracturing sand backflow frequently occurs during the wiper trip or workover operations in deep CBM wells. This phenomenon leads to issues such as tubing erosion, sand accumulation and blockage, and production decline, which directly affect the estimated ultimate recovery (EUR)of a single well. The variation in the conductivity of supporting fractures is therefore a critical factor influencing gas production performance in deep CBM reservoirs and plays a key role in establishing appropriate fluid drainage strategies. However, existing commercial simulators fail to incorporate the influence of velocity-sensitivity effects and thus cannot characterize proppant transport and fracture conductivity evolution during the drainage and production process. As a result, the production forecast accuracy for CBM wells remains low, making it difficult to establish a scientifically based and quantitatively optimized flowback strategy. To address these challenges, core flooding experiments and particle mechanics analyses were first conducted to investigate the influence mechanisms of factors such as sand concentration, proppant particle size, and effective stress on the velocity sensitivity characteristics of fracture conductivity in deep coal seams. Based on the experimental findings, a dynamic conductivity characterization model considering the effect of flow velocity was then developed. By coupling this model with a discrete fracture model and a dual-porosity single-permeability coal seam model, the study establishes a numerical simulation method considering the effects of fracture conductivity changes. This method ultimately enables the determination of a reasonable flowback strategy. The results indicate that:(1)With the increasing of flow velocity, the fracture conductivity in deep coal seams first rises and then declines, exhibiting a peak at the flow velocities between 2.5 and 7.5 mL/min. The variation amplitude of conductivity is positively correlated with proppant placement concentration, particle size, and fluid viscosity, while being negatively correlated with effective stress. (2)The intrinsic mechanism governing the dynamic variation of fracture conductivity in coal rock systems lies in the dual effect of fluid flow on proppant behavior. At low flow velocities, the flushing and sand-carrying action of the fluid on small-sized proppant particles exerts a positive effect by clearing and widening the flow channels. In contrast, at high flow velocities, the fluid tends to displace large-sized proppant particles that provide structural support, producing a negative effect by promoting fracture closure. (3)Numerical simulation results that incorporate the velocity sensitivity characteristics of fracture conductivity indicate that the velocity sensitivity effect significantly reduces gas production performance. Therefore, it is necessary to control the flowback rate to mitigate the adverse impact of velocity sensitivity effects. (4)The production practices in Daji block have verified that the fracturing sand backflow volume and gas production performance of CBM wells are both governed by the liquid production rate. Based on comprehensive analyses combining physical experiments, numerical simulations, and field monitoring data, it is recommended that the flowback rate for a single layer of vertical well should be maintained at 20-23 m ³/d, with a maximum daily liquid production not exceeding 23 m ³/d. For horizontal wells with the single-stage fracturing parameters and stimulation effects similar to those of vertical wells, the maximum daily liquid production should not exceed (number of stages × 23)m ³/d. The field application in Daji Block demonstrates that the maximum daily liquid production of CBM horizontal wells has been effectively reduced from 634 m ³/d to below 230 m ³/d. As a result, the occurrence of fracturing sand backflow is significantly mitigated, and gas production performance is markedly improved. These findings provide both theoretical support and technical guidance for formulating a reasonable flowback strategy for deep CBM wells.

Driven by the accelerated transformation of global energy structure and the strategic goal of carbon neutrality, the comprehensive utilization of deep underground space (below 500 meters)has become a crucial approach to ensuring national energy security and achieving green, low-carbon development. By reviewing the comprehensive utilization of underground space both domestically and internationally, the current status and future development directions of the "2334" foundational theory have been clarified. These include two fundamental theories:dynamic sealing of gas storage geological bodies and partitioned, differential utilization of porous medium gas storage space. Additionally, three key technologies are identified:efficient cavity construction in salt caverns, large displacement drilling and production techniques, and tripartite risk monitoring-early warning system. Three common technology development directions are highlighted:cross-scale small molecule sealing, efficient peak shaving operation, and coordinated optimization of the entire system. Furthermore, four frontier technology development directions are outlined:controllable transformation for increasing production in low permeability reservoirs, compressed air energy storage, helium storage capacity loss evaluation, and non-hydrocarbon cushion gas replacement. The utilization layout of deep underground space, characterized by "East-West collaboration and multi-energy complementation", is proposed. This includes the establishment of six gas storage centers with a capacity of 100 billion cubic meters, the dual mode of "production site + receiving" for helium storages, the construction of hydrogen storages around wind and solar hydrogen production bases, forming a "west-to-east gas and salt" pattern, and the deployment of compressed air energy storages tailored to local conditions. A comprehensive analysis shows that the scientific utilization of China’s abundant deep underground resource space can enable the efficient storage of multiple media, including natural gas, hydrogen, compressed air, and helium. This will significantly facilitate the integrative development of oil, gas and new energy sectors, serving as a strategic direction that strongly supports the enhancement of China's energy system resilience and the achievement of the "3060" dual carbon goals.

Against the backdrop of China’s efforts to build a new energy system, the upstream operations of PetroChina have taken the "dual carbon" goals as a guiding framework, coordinating steady oil production, increased gas supply, and low-carbon transformation. By identifying key breakthroughs and focal areas for integrated development, PetroChina has progressively clarified its transition pathway and established a theoretical understanding of integrated development with distinct PetroChina characteristics. By upholding a dual-driven approach of internal clean energy replacement and external clean energy supply, the company has successfully developed a series of low-carbon and zero-carbon demonstration projects. These initiatives have not only expanded oil and gas supply but also effectively reduce carbon emissions, fostering an effective model for the mutually reinforcing and coordinated development of oil, gas and new energy. Significant progress has been achieved in low-cost green power development, clean energy substitution for energy use in oil and gas production, and negative-carbon industrial initiatives This demonstrates that the "two-way integration" between oil, gas and new energy is an inevitable choice for achieving high-quality and sustainable development. Such mutually reinforcing and win-win interactions will play a crucial role in the construction of a modern energy system. As integrated development deepens and progresses from the initial stage of technological superposition to profound ecological restructuring, oilfield enterprises should build on their inherent strengths, tap their potential, and promote integration across Sources-Grids-Loads-Storage. Further efforts should be directed toward strengthening technological innovation, scenario integration, industrial collaboration, and management restructuring, thereby establishing an energy ecosystem encompassing oil, gas, heat, power, hydrogen, and carbon. Enterprises should expand low-carbon initiatives, implement zero-carbon pilot projects, and explore negative-carbon reserves. These efforts will actively integrate into the construction of the national new-energy system and advance the low-carbon transformation of oilfields in greater depth.

Although the Whole Petroleum System theory has gained substantial attention, an effective evaluation and characterization framework is still lacking. Following the core concept of "element-evolution-distribution", a research framework for the Whole Petroleum System was established. Taking the Whole Petroleum System of Qingshankou Formation in Qijia-Gulong sag of Songliao Basin as the study case, this paper systematically elucidates its evolutionary processes and distribution patterns, and develops a characterization system comprising six maps and one table, i.e., comprehensive static element map, burial history map, hydrocarbon accumulation event map, hydrocarbon ordered distribution map for key strata, profile distribution map, planar distribution map, and hydrocarbon summary table. The main findings are as follows. (1)The "element-evolution-distribution" integrated research concept was systematically proposed. Taking the Qingshankou Formation in Qijia-Gulong sag as a representative case, a Whole Petroleum System research framework suitable for continental basins was established, which provides a paradigm for studying the Whole Petroleum System in comparable geological settings. (2)The dynamic evolutionary process of conventional and unconventional reservoirs in the Whole Petroleum System of Qingshankou Formation was clarified. It was identified that at the end of Nenjiang Formation deposition, the source rocks of Qingshankou Formation entered the peak hydrocarbon-expulsion stage while the reservoirs had not yet undergone compaction, allowing conventional oil to accumulate first. From the end of Nenjiang Formation deposition to the end of Mingshui Formation deposition, source-reservoir systems evolved synergistically. The reservoirs were progressively tightened and trapped high-maturity oils, thus forming tight oil reservoirs. The key retention period for shale oil was from Nenjiang Formation deposition stage to the Early Paleogene. (3)The spatial distribution of the Whole Petroleum System of Qingshankou Formation in Qijia-Gulong sag was described at two hierarchical levels, i.e., the internal stratigraphic distribution and the overall system-wide distribution. In Qingshankou Formation, shale oil, tight oil, and conventional oil reservoirs develop successively from the basin center toward the margins, exhibiting an orderly spatial pattern. (4)The "six-map-and-one-table" characterization system was established for the first time, enabling a comprehensive depiction of the Whole Petroleum System across multiple dimensions, including geological element assemblages, geological evolutionary processes, temporal-spatial coupling of hydrocarbon accumulation, and spatial distribution characteristics. This study advances and refines the Whole Petroleum System theory and provides theoretical and technical support for hydrocarbon exploration in continental basins.

To address the climate crisis caused by global high carbon emissions, China is promoting the transformation of traditional energy bases into super energy basins with multi-energy complementary systems through "dual carbon" strategy. As one of China’s super oil and gas basins, the Junggar Basin, with its resource advantages and strategic position, possesses unique conditions for establishing a carbon-neutral demonstration zone. The oil and gas resources in the Junggar Basin exceed 100×10 ⁸ tons of oil equivalent, and it also has abundant potential for the development of new energy sources such as wind, solar, and natural hydrogen. The basin’s carbon source reserves, combined with the advantages of source-sink matching for carbon capture, utilization, and storage (CCUS)/carbon capture and storage (CCS) technologies, make it capable of achieving internationally leading carbon sequestration capabilities. To build a collaborative development system for traditional and new energy, this paper proposes a diversified integration model of coal, oil, natural gas, new energy, and CCUS/CCS, aiming to achieve efficient multi-energy integration through the implementation of four major innovative projects:(1) the 20 million-ton crude oil production growth project to ensure energy security; (2) the 10-billion-cubic-meter gas production project to optimize the supply structure; (3) the 20 million-ton new energy development project to advance green transformation; (4) the ten million-ton comprehensive CCUS/CCS project to solidify the foundation for carbon neutrality. In the practice of constructing a carbon-neutral "super energy basin", the Junggar Basin has addressed the challenge of low-carbon transformation of fossil energy by optimizing the energy structure, building a new industrial ecosystem, and enhancing supply capacity, providing a Chinese solution for global climate governance.

Due to deep burial and complex diagenesis, tight sandstone reservoirs are characterized by low porosity, low permeability, and extreme heterogeneity. Accurately identifying and predicting high-quality reservoirs is a critical foundation for the efficient development of tight gas. Existing methods for predicting high-quality reservoirs, which relies on geological theoretical models and geophysical theories, fail to meet the degrees of accuracy, effectiveness, and applicability required for hydrocarbon exploration and development. This paper is a case study of the Oligocene Huagang Formation tight sandstone reservoir in Block H of Xihu sag, East China Sea shelf basin. Using core, logging, and seismic data, a seismic prediction method based on the coupling of sedimentary microfacies, lithofacies, and diagenetic facies is proposed for high-quality reservoirs. This method achieves accurate prediction of high-quality tight sandstone reservoirs. The research results show as follows. (1)The combined characterization of core, logging, and seismic data clearly defines the distribution of sedimentary microfacies. The integration of logging cross-plot analysis and stepwise discriminant analysis significantly enhances the accuracy of lithology identification and interpretation. The high-quality reservoirs of Huagang Formation in Block H of Xihu sag develop in the medium sandstone facies belt of the underwater distributary channel. (2)The diagenetic facies are quantitatively classified based on the flow zonation index, and machine learning is applied to achieve intelligent logging interpretation and macroscopic prediction of diagenetic facies. Under the dual constraints of sedimentary microfacies and lithofacies, high-quality reservoirs are precisely located. (3)The three-phase coupling model indicates that high-quality reservoirs are distributed in the overlapping zone of the underwater distributary channel sedimentary microfacies, medium sandstone lithofacies, and strong dissolution diagenetic facies. The analysis effectively reduces ambiguity and significantly improves prediction accuracy, providing a new approach for predicting high-quality tight sandstone reservoirs.

The dry hot rock(HDR) geothermal resources are abundant and have great development potential, which is of great strategic significance to the transformation of China’s energy structure and the realization of the "double carbon" goal. However, HDR drilling faces extreme geological challenges such as high temperature, high rock hardness, high in-situ stress, and low permeability, leading to low rock-breaking efficiency, high risks of wellbore instability, and accelerated failure of drilling tools and working fluids, which severely hinders its cost-efficient development. This paper analyzes the drilling engineering practice of enhanced geothermal system (EGS) at home and abroad, sorts out the core technical challenges of hot dry rock drilling, and focuses on the technical development status of hot dry rock wellbore stability, hot dry rock drilling rate-of-penetration (ROP) enhancement techniques and wellbore working fluid system. The analysis indicates that significant progress has been achieved in the research of major technical fields such as wellbore stability control, efficient rock breaking and ROP enhancement, and high-temperature-resistant drilling fluids, while challenges persist in the long-term thermal stability of tools, the process system integration, and intelligentization level. Therefore, from the perspective of national strategy and engineering needs, recommendations are proposed for the systematic development, including the breakthroughs in full-system high-temperature-resistant drilling system, advance in the integration of customized processes with intelligent systems, development of "intelligent regulation and functional synergy" type drilling fluid systems, establishment of a Chinese technical standard mode, and design of next-generation rock-breaking methods. These recommendations aim to provide decision-making references for breakthroughs in HDR drilling technology and the large-scale development of deep geothermal resources in China.

A significant breakthrough has been achieved in the hydrocarbon exploration of the lower assemblage in Dongwan structural belt along the southern margin of Junggar Basin. During formation testing, Well QB1 obtained a high industrial oil and gas flow from the Cretaceous Qingshuihe Formation, with the gas output of 50.7×10 ⁴m ³/d and oil production of 288 t/d. This demonstrates favorable hydrocarbon accumulation conditions and significant exploration potential in this belt. The result of research shows as follows. (1)Multiple sets of large-scale source rocks are developed in Dongwan structural belt, dominated by the Jurassic humic-type source rocks, while oil reservoirs are contributed by the mixture of Permian sapropelic-type and Cretaceous mixed-source rocks. (2)The Qingshuihe Formation features a dual reservoir system comprising basal sandstone and fracture networks, exhibits low matrix porosity but achieve high and stable hydrocarbon production through pore-fracture dual media under overpressure conditions. (3)The lower assemblage has favorable geological conditions such as high-quality reservoir-cap combinations and wide and gentle structural trap groups. (4)The favorable temporal matching between trap formation and hydrocarbon generation-expulsion peaks has laid the foundation for hydrocarbon accumulation in large gas fields. The exploration breakthrough of Well QB1 demonstrates that the natural gas resource potential of Dongwan structural belt is estimated to be 100 billion cubic meters, providing important practical evidence for deep to ultra-deep exploration in the northern Tianshan piedmont. The current exploration of lower assemblage in the southern margin of Junggar Basin mainly focuses on increasing reserves and enhancing productivity in the Hutubi, Dongwan, and Wuchang structural belts, while simultaneously accelerating exploration breakthroughs in replacement zones and reserve areas.