Coal-rock gas is a new type of natural gas discovered in recent years, generally buried deeper, and some scholars also call it as deep coalbed methane. The exploration and development of this type of natural gas has made rapid progress, with significantly increasing production. Preliminary research indicates that deep coal-rock gas differs significantly from traditional coalbed methane, shale gas, tight gas, and other gas reservoirs in terms of reservoir characteristics and development methods, and has the potential to become a strategic replacement resource for natural gas in China. Therefore, a new round of national science and technology major projects for oil-gas exploration and development will focus on a series of scientific and technological breakthroughs in deep coal-rock gas. Based on systematical analysis, this paper summarizes the three major scientific challenges and ten key research directions for coal-rock gas exploration and development as follows. (1)The key fundamental geological issues are the accumulation mechanism of coal-rock gas and the construction of coal-measure whole petroleum system. The main research directions include the whole process mechanism of hydrocarbon generation/expulsion and enrichment lower limit of coal rocks, sedimentation and source-reservoir coupling effect of coal measures, multiple reservoir types and structures of coal rocks, and coal-measure whole petroleum system and oil-gas distribution. (2)The key fundamental development issues are the flow mechanism and migration regularities of fluid in coal beds. The main research direction include the occurrence state and migration mechanism of coal-rock gas, controlling factors of fluid co-production in coal reservoirs, and stereo development models of complex fluid systems in multiple (thin)reservoirs. (3)The key fundamental engineering issues are the mechanical characteristics and fracture propagation regularities of coal-rocks. The main research directions include the mechanical characteristics and fracturing mechanism of coal rocks, the interaction mechanism between coal rock and fracturing media, and the instability mechanism of coal reservoirs. The analysis of the above-mentioned major scientific issues and key research directions will provide important support for the efficient exploration and development of deep coal-rock gas, and lay the foundation for improving the geological theory of coal-rock gas with Chinese characteristics and coal measure whole petroleum system.

The research of Whole Petroleum System (WPS) theory, emerging as a frontier field in the petroleum and natural gas geology at present, has attracted extensive attention from both the petroleum industry and academic community since its proposal. Expanding beyond the traditional concepts of petroleum systems, the research of WPS theory involves the geological regularities and resource development of unconventional oil and gas, representing an evolution and development of the petroleum system theory. This paper elucidates the fundamental principles of WPS theory, and summarizes the research progress during its development, including:(1) research advances and exploration practices of the Permian WPS in Junggar Basin; (2) the differential enrichment in the sequential distribution pattern of conventional and unconventional oil and gas, as well as the hydrocarbon accumulation and enrichment mechanism controlled by "source-reservoir coupling"; (3) hydrocarbon migration models in WPS; (4) analysis of WPS in sedimentary basins with the development of multiple sets of source rocks; (5) research and development of the new-generation basin modeling technology and genesis-based hydrocarbon resource appraisal methods on the basis of WPS theory.

Intelligent drill bits are one of the core components of future intelligent drilling systems. By integrating sensors capable of stable performance under high-temperature and high-pressure conditions, adaptive control algorithms, and optimized drill bit structures, these advanced drill bits enable real-time downhole condition monitoring, dynamic adjustment, and precise execution, thereby improving drilling efficiency. As oil and gas exploration expands to ultra-deep formations and complex, unconventional reservoirs, drill bits face increasingly harsh geological conditions. Traditional drill bits, under high-temperature and high-pressure environments and complex geological settings, suffer from challenges such as rapid wear, short service life, and high drilling costs that urgently demand the development and application of high-performance drilling technology. This further highlights the importance of intelligent drill bits as a pivotal future direction for improving drilling speed and efficiency. By systematically summarizing and analyzing the current research, core technologies, and product advancements in intelligent drill bits, such as multi-parameter sensing technology capable of withstanding extreme downhole environments, machine learning- and deep learning-based adaptive control algorithms, and progress in drill bit structure and control mechanisms, this work reveals the potential of intelligent drill bits in modern drilling operations. Typical case studies from both domestic and international projects demonstrate the advantages of intelligent drill bits in enhancing rate of penetration, extending bit life, and reducing unplanned downtime. Looking ahead, research on intelligent drill bits will move toward higher autonomy, broader adaptability, and deeper integration with digital platforms. They are poised to play an even greater role within the intelligent drilling technology framework.

Xihu sag in the East China Sea Basin is the largest hydrocarbon-bearing sag in China's offshore area, and is also one of the main battlefields for offshore natural gas exploration and development in China. In the past five years, based on the "positive rhythm channel sand dessert" seismic prediction while drilling monitoring technology, "permeability classification-dessert thickness ratio" high-efficiency well type design and productivity evaluation technology, and oil-based mud long open hole productivity release technology, the geological-engineering integration technology system innovation and effective practice have been carried out. Xihu sag has obtained commercial gas flow in many low-ultra-low permeability fields, showing good potential for low-ultra-low permeability natural gas storage and production. Based on the analysis of core, mud logging, logging, seismic and other geological data and the exploration and development practice of typical gas reservoirs, the accumulation characteristics and resource potential of low permeability and ultra-low permeability natural gas reservoirs in Xihu sag are systematically analyzed. The Eocene Pinghu Formation in the Xihu sag develops two types of source rocks:the delta-tidal flat facies coal measure source rock in the slope zone and the tidal flat-lagoon facies sapropelic humic source rock in the sag area, showing a full-sag distribution pattern. The tidal flat sedimentary system of Pinghu Formation has the near-source enrichment conditions of natural gas with "self-generation, self-storage and self-cover", and the natural gas accumulation conditions are superior. Controlled by the structural pattern of "east-west zoning and north-south block", three new models of differential enrichment of natural gas are developed in the central anticline belt of Xihu sag. The lithologic oil and gas reservoirs of Pinghu Formation in the western slope zone have the oil and gas distribution law of "vertical superposition and horizontal connection". The large-scale structural traps in the north of the central anticline belt, the lithologic traps in the wing of the central and southern anticlines, the deep Pinghu Formation in the south and the near-sag areas in the western slope belt are the key exploration directions for the low-permeability and ultra-low-permeability gas reservoirs in Xihu sag. The natural gas resources exceed 500 billion cubic meters.

The cumulative hydrocarbon production in the oilfields in the eastern South China Sea has achieved nearly 400 million tons of oil equivalent over the years, making outstanding contributions to China’s energy security and economic construction. However, after more than 40 years of exploration and development, the remaining potential of conventional oil and gas is exhausted, and the deep oil and gas have become strategic replacements for guaranteeing sustainable reserves and production. This study focuses on the key issues encountered by oil and gas exploration in deep formations, such as basin formation, hydrocarbon generation, reservoir formation, and hydrocarbon accumulation. Using three-dimensional seismic, drilling data, and core analysis results, the hydrocarbon accumulation conditions in deep to ultra-deep reservoirs were systematically investigated from multiple perspectives, including the formation mechanism of hydrocarbon-rich sags/subsags, development mechanism of effective reservoirs, and hydrocarbon enrichment patterns. This provides new geological insights as below. (1)The composite continental-margin magmatic arcs control the formation and evolution of large lake basins. (2)Potassium-rich fluid transformation controls the development of effective reservoirs. (3)Seal and migration mechanism of transtensional fault systems controls hydrocarbon migration, accumulation, and enrichment. These findings guided the integrated evaluation and cluster drilling of the Huizhou 19-6 structure, leading to the discovery of billion-ton-scale oilfield in deep to ultra-deep clastic formations in China’s offshore area. The discovery of the Huizhou 19-6 structural oilfield further reveals that deep oil and gas of the Pearl River Mouth Basin are important replacements for the future growth of hydrocarbon reserves and production, demonstrating the huge exploration potential of deep to ultra-deep reservoirs in the offshore high-geothermal, highly tectonically active composite continental-margin basins, which provides important reference and inspiration for the exploration of petroliferous basins with similar structural settings.

The current study mainly focus on the application of intelligent methods to improve the efficiency and reliability of technologies for optimizing parameters and identifying operational states in drilling and production processes, which exhibit great potential for future development. However, in the development of intelligent engineering technologies for oil and gas drilling and production, the smart optimization algorithms and predictive models still face the challenges including poor timeliness, weak robustness, and limited reliability. This hinder the practical application of artificial intelligence (AI)methods in oil and gas engineering. The paper provides an overview of the development status of AI methods and intelligent technologies for oil and gas drilling and production in China and abroad, involving engineering design and parameter optimization for well drilling and completion, evaluation of hydraulic fracturing performance and optimization of process parameters, diagnosis of artificial lift system failures, and prediction of reservoir properties and productivity. It further summarizes and analyzes the major challenges including a heavy reliance on labeled data for model training, poor model interpretability and weak performance in small-sample learning, inadquate validation of engineering applicability and reliability, poor timeliness of AI methods in performing optimization tasks, and limited flexibility in multi-objective optimization decision-making methods. Based on aforementioned challenges and the current research state of drilling and production technologies in China’s petroleum industry, this paper proposes several suggestions for the development of AI methods in oil and gas drilling and production as below:(1)establishing standardized, shared industry databases to support intelligent model comparison and validation; (2)enhancing research on learning paradigms to reduce the dependency on labelled data; (3)strengthening research on intelligent optimization methods to improve decision-making efficiency and timeliness; (4)focusing on studying physics-contrained data-driven models to improve the reliability of hybrid physics-data driven models; (5)advancing research on sample balancing and augmentation techniques to improve minority class recognition and model stability; (6)making efferts to develop multimodal data fusion and processing methods to boost the prediction accuracy and engineering robustness of intelligent models; (7)leveraging the advantages of general and industry-specific large models to enhance interpretability and accuracy of intelligent optimization decision-making for drill and production operations under multiple scenarios.

The Whole Petroleum System (WPS) theory has broken through the traditional exploration theoretical framework, with "source-reservoir coupling and orderly accumulation" as its core concept. This theory has proven effective in guiding the coordinated exploration and development of both conventional and unconventional oil and gas resources in northern Xinjiang area of China. In this region, there are three sets of organic-rich source rocks, i.e., the Jurassic, Permian, and Carboniferous-Devonian source rocks, with a total resource of 25 billion tons oil equivalent. Under the guidance of this theory, major breakthroughs have been made in three-dimensional multi-layer exploration across Junggar Basin, Tuha Basin, and Santanghu Basin. Successive reserve discoveries of shale oil in Fengcheng Formation of Mahu sag and tight oil in Jimusaer sag have been achieved over 100 million tons in Junggar Basin. Hydrocarbon exploration in the Shiqiantan sag of Junggar Basin (Carboniferous marine residual strata), Taibei sag of Tuha Basin (Jurassic coal strata), and Tiaohu-Malang sags of Santanghu Basin (Permian strata) has systematically revealed the distribution patterns of various types of oil and gas reservoirs. These findings have enabled the successful, coordinated development of both conventional and unconventional resources. Research has shown that the oil and gas accumulation in northern Xinjiang area exhibits distinct spatial zoning patterns, forming a complete distribution sequence:in-source shale oil-gas in the center, tight oil-gas with variable saturations in the slope zones, and conventional reservoirs along the basin margins. The accumulation mechanism involves multiple dynamic processes, such as buoyancy-driven migration, self-containment effects, and pressure differentials between source and reservoir, demonstrating the dynamic evolution of WPS. Future research should focus on the development of unconventional in-source resources, achieve breakthroughs in key technologies for nano-scale reservoir stimulation, advance the study of dynamic mechanisms governing the whole process from hydrocarbon generation to reservoir formation and accumulation, and establish a comprehensive evaluation technology system for WPS. Exploration practices in northern Xinjiang area have demonstrated both the scientific validity and practical value of the WPS theory, while also offering an innovative paradigm for exploring geologically complex petroliferous basins, which is of strategic significance to national energy security.

As the primary oil-generating source rocks in Junggar Basin, Fengcheng Formation source rocks are relatively understudied in terms of their gas generation processes, which impedes the target natural gas exploration in this region. This paper aims to clarify the whole-process gas generation pattern and gas accumulation characteristics of Fengcheng Formation source rocks in western Junggar Basin. Based on hydrocarbon generation simulation experiments in combination with the geochemical characteristics of source rocks, hydrocarbon generation evolution process, and hydrocarbon inclusion observation, a comprehensive analysis was conducted on the product characteristics of Fengcheng Formation source rocks at different maturity stages in the study area. The results show as follows. (1) Based on the variations in gas-oil ratios during hydrocarbon generation from Fengcheng source rocks in western Junggar Basin, the gas generation process can be divided into seven stages:biogenic gas, gas associated with immature/low-mature oil, gas associated with black oil, gas associated with light oil, gas condensate, wet gas, and dry gas. Thus, a whole-process gas generation pattern has been established for Fengcheng Formation source rocks. (2) The paper clarifies the geochemical characteristics of Fengcheng Formation source rocks during the whole-process gas generation. As the maturities of Fengcheng Formation source rocks gradually increases, the carbon isotopes of natural gas and some parameters of light hydrocarbons demonstrate a gradual increasing trend. The carbon isotopes of ethane increase gradually from -38 ‰ to -28 ‰, and the paraffin index gradually increases to above 6. (3) The western Junggar Basin exhibits the high charging intensities for gas associated with light oil, gas condensate, wet gas and dry gas, indicating great potential for both in-source and extra-source natural gas exploration in this area. These research findings can further enrich the geological theory of the Whole Petroleum System in Junggar Basin and promote the efficient exploration of natural gas.

This study aims to provide theoretical guidance for the exploration direction in Baoding sag and Raoyang sag of Jizhong depression, Bohai Bay Basin. Specifically, the overall oil and gas resource types and migration distribution characteristics of both sags were analyzed based on the Whole Petroleum System theory in combination with regional hydrocarbon geological features. Through hydrocarbon generation-expulsion modelling of source rocks in different strata, the resource potential of various hydrocarbons was calculated, and the models of hydrocarbon accumulation in different formations were established. The results show as follows. (1)The source rocks of Member 1 of Shahejie Formation in Baoding sag are characterized by early hydrocarbon generation and expulsion, reaching the hydrocarbon generation and expulsion thresholds at vitrinite reflectance values of 0.35% and 0.45%, respectively. (2)The Whole Petroleum System in Baoding-Raoyang sags have their own vertical boundaries and converge near the Gaoyang low-uplift, which jointly contribute to the development of oil and gas reservoirs near Gaoyang fault. (3)The total hydrocarbon yield from different source rocks of Baoding-Raoyang sags is 73.94×10 ⁸t, with the retained hydrocarbons of 48.67×10 ⁸t in shale, indicating huge exploration potential. (4)Comprehensively considering the Whole Petroleum System, the accumulation modes are divided as the shallow hydrocarbon accumulation model characterized by dual source hydrocarbon supply, fault adjustment, and shallow enrichment in Dongying Formation in Baoding sag, the middle and deep hydrocarbon enrichment mode characterized by migration along slopes and faults, distribution around subsags, and local enrichment in buried hills in Raoyang sag, and the oil and gas enrichment model characterized by near-source migration and intra-source accumulation in both tight and shale reservoirs.

The Permian Fengcheng Formation in the Well Pen-1 West sag of Junggar Basin is one of the key strata for natural gas exploration. Previous source-proximal exploration led to occasional modest-scale breakthroughs. In 2023, the Well WT1 deployed in the Mosuwan uplift achieved high-yield industrial gas flow, thus confirming the exploration potential of Fengcheng Formation. This provides a basis for identifying new gas replacement plays, and is of great theoretical and practical significance. To further advance exploration, a study was carried out to investigate the gas accumulation elements and mechanisms using high-precision seismic data and exploration drilling results from multiple wells. The study shows as follows. (1) Glutenite reservoirs are developed in Member 3 of Fengcheng Formation in the source-proximal uplift area of the Well Pen-1 West sag. In the in-source slope area, the Member 2 and Member 1 of Fengcheng Formation are developed. The Member 2 of Fengcheng Formation is primarily composed of mudstone, as the primary hydrocarbon source rock, and the Member 1 of Fengcheng Formation is dominated by lowstand sandstone and dolomitic sandstone. (2) In the in-source slope area of the Well Pen-1 West sag, Fengcheng Formation develops retrogradational braided river delta sedimentary reservoirs, conventional stratigraphic-lithologic gas reservoirs in the source-proximal zone under the background of sedimentary overlap, and continuous tight sandstone gas reservoirs in the source rock. Exploration in the Well Pen-1 West sag has been extended into the in-source slope area, identifying a favorable exploration zone of exceeding 3 000 km ². With the natural gas resource potential exceeding 400 billion cubic meters, this area is expected to become one of the primary targets for natural gas exploration and development in Junggar Basin.

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 proposal of the Whole Petroleum System (WPS) theory has significantly enhanced the understanding of hydrocarbon accumulation theories, thus facilitating a series of major exploration breakthroughs in multiple basins in China. This study focuses on the hydrocarbon exploration and development in Junggar Basin, with an aim to further develop and refine the WPS theory and guide domestic and international oil and gas exploration and development. Initially, through analysis of new challenges posed by WPS to seismic exploration technology, the paper elaborates in detail on the research progress of seismic exploration technology and predicts its development trends. The research results show as follows. (1) The WPS theory poses three challenges to seismic exploration technology, i.e., achieving ultra-high shot and trace density acquisition and massive data processing, addressing the issue of coupling diverse target objects and multi-scale data, and enhancing seismic resolution and prediction accuracy. (2) During hydrocarbon exploration in Junggar Basin, four key technological breakthroughs have been achieved. Specifically, the seismic data acquisition technology has undergone a leap from conventional three-dimensional surveys to wide-band, wide-azimuth, and high-density nodal acquisition with high efficiency, the seismic data processing technology has further improved high-resolution, high-fidelity, and high-precision processing techniques, a basin-level high-precision seismic data platform has been established based on new seismic acquisition and processing technologies, and the progress in interpretation technologies such as discrete element numerical simulation, intelligent seismic facies characterization, multi-attribute interpretation of strike-slip faults, geological and engineering "sweet spot" reservoir prediction, and seismic-geological-engineering integration has provided new methods for studying the "tectonic system, sedimentary system, hydrocarbon transport system, accumulation system, and engineering support system" in WPS. (3) Three development trends in seismic technology for WPS exploration have been identified, i.e., seismic acquisition technology centered on ultra-high density, multi-wave and multi-component, seismic data processing technology promoted by the coordinated development of intelligent, high-performance computing and high-resolution imaging, and seismic interpretation technology with intelligent, quantitative, and dynamic characteristics.

The Junlian coalbed methane field in southern Sichuan Basin, as a mountainous coalbed methane field that has achieved large-scale commercial exploitation within the shallow transformation area in southern China, has maintained a stable coalbed methane output of over 1×10 ⁸m ³/a for eight consecutive years. The Junlian coalbed methane has the characteristics of mountainous coalbed methane, which are "located in a complex mountainous area, developed in thin coal seams under the control of waves and tidal flats, deeply buried in the early stage with high-rank coal for hydrocarbon generation, underwent shallow transformation for reservoir adjustment and occurrence in the late stage, had low permeability of coal rock, and contained adsorption gas at normal pressure". Compared with other coalbed methane fields at home and abroad, the efficient exploration and beneficial development of the Junlian coalbed methane fields are confronted with "two deficiencies" (no experience in the exploration and development of high-rank coalbed methane in thin interbedded coal seams on plateau and mountainous areas, and no mature drilling and pressure production technology for karst landforms to draw upon)and "four difficulties" (difficulty in the deployment of sweet spot selection in Wumeng Mountain area, difficulty in implementing drilling and pressure production technology under the karst geological conditions on the surface of karst landforms, difficulty in intelligent and precise drainage and production for low-yield water pressure reduction, and difficulty in gathering and transporting mountainous coalbed methane with low production, low pressure and low cost). Based on the characteristics and technical difficulties of shallow transformation of thin interbedded coal seams faced by the Junlian coalbed methane field, through systematic research on the accumulation laws and key technologies of coalbed methane, it has been clarified that the coalbed methane reservoir of the Upper Permian Leping Formation in southern Sichuan Basin has the characteristics of "shallow transformation, over-maturity with high-rank coal, thin layer, low permeability, low pressure and low water content". The occurrence and enrichment mechanism of shallow and thin interbedded coalbed methane reservoirs in mountainous areas, namely "tidal flat and marsh controlling coal seams, early deep burial-thermal evolution controlling hydrocarbon generation, late and shallow adjustment controlling gas reservoirs, and current retention-confined water area controlling sweet spot enrichment", has been revealed. A sweet spot model of "wide and gentle syncline rich gas" in residual structural depression under the basin-mountain coupling effect of shallow transformation has been established. The technical difficulties in the exploration and development of mountainous coalbed methane under the karst geological conditions of the exposed carbonates have been overcome. A series of continuous and effective exploitation technologies for shallow low-pressure coalbed methane in complex mountainous areas have been established, featuring "low cost, practicality and high efficiency", including integrated sweet spot evaluation and deployment design, factory rapid drilling and fracturing, intelligent precise pressure control drainage and production, as well as integrated production and sales of surface gathering and transportation. The successful development of the Junlian coalbed methane field marks a crucial step forward for the coalbed methane industry in southern China. Its exploration geological theory and key development technologies have promoted the formation and application of the "Junlian Model", providing an important demonstration for the efficient utilization and industrial chain development of the same type of shallow, thin-interlayer and high-rank coalbed methane resources in southern China and other regions.

Mahu sag in Junggar Basin develops a typical Whole Petroleum System (WPS), which exhibits the ordered distribution of conventional and unconventional hydrocarbon reservoirs. This has important implications for advancing the development of petroleum geology theories. Through systematic analysis of the petroleum accumulation elements in WPS, the paper summarizes the hydrocarbon enrichment patterns in the study area. Specifically, the WPS of Mahu sag is characterized by distinctive alkaline lacustrine source rocks with sustained hydrocarbon generation throughout the thermal evolution, diverse reservoir types developed across all grain-size sequence (from sandy conglomerates to dolomitic siltstones and argillaceous mudstones), three-dimensional distribution of hydrocarbon transport system enabling efficient oil and gas migration, and a diverse range of orderly accumulated hydrocarbon reservoirs. The source-reservoir configuration, along with their spatiotemporal coupling with hydrocarbon accumulation, forms the core of WPS. Since the end of the Permian period, the Fengcheng Formation source rocks have undergone continuous burial and multi-phase hydrocarbon generation and expulsion, thereby providing a sustained resource basis for hydrocarbon accumulation; the development of sandy conglomerate, dolomitic siltstone and argillaceous shale reservoirs across all grain-size sequence controls the ordered distribution of both conventional and unconventional hydrocarbon reservoirs. The WPS of Mahu sag undergoes sustained and temporally sequenced hydrocarbon charging, demonstrated by early-stage accumulation in conventional far-source reservoirs while later-stage accumulation in unconventional intra-source shale oil and gas reservoirs. The study reveals the whole-process accumulation mechanism of WPS and highlights unconventional intra-source resources as a key frontier for deep exploration. These findings are valuable for refining WPS theory and guiding future exploration practice.

In the eastern slope area of Shijiutuo uplift of Bohai Sea, the main oil-bearing strata is the Lower Member of Neogene Minghuazhen Formation. Conventionally, it is believed that the hydrocarbons only pass through the transport layer in Neogene Guantao Formation, without any retentions. Moreover, the Lower Member of Minghuazhen Formation is dominated by small-scale river channel deposits, leading to poor exploration efficiency. Based on the drilling, seismic, and geochemical data, combined with physical simulation experiments of hydrocarbon migration, studies were carried out on the hydrocarbon enrichment patterns in the Lower Member of Minghuazhen Formation in the slope area of the uplift. The results show as follows. (1)The eastern Shijiutuo uplift is adjacent to Bozhong depression and Qinnan depression, of which the source rocks are of good organic matter type and high maturity. Shahejie Formation in Bozhong depression is the main hydrocarbon source rock strata. (2)The activity rate of Shijiutuo No.1 fault was relatively large in the later stage, and the Paleogene fan bodies were generally developed on the downthrown side of faults, and playing the role of hydrocarbon transfer station. The assemblage of faults and fans bodies promotes the large-scale hydrocarbon vertical migration. (3)The transport layer of Neogene Guantao Formation in the eastern Shijiutuo uplift is located on a wide and gentle slope, with the slope angle generally less than 1.0°, providing favorable conditions for the retention of crude oil in transport layer. (4)Under the control of the pre-existing No.1 and No. 2 strike-slip faults, the strike-slip adjusted faults were formed in the shallow layers of Shijiutou uplift in the later period. By contrast, No. 2 strike-slip fault has relatively stronger activity, and the corresponding strike-slip adjusted faults have longer extension distances thus facilitating the vertical migration of crude oil from Guantao Formation to the Lower Member of Minghuazhen Formation. (5)Under the background of the arid climate in the Neogene, the supply capacity of the sediment source was enhanced, and the river channel was prone to frequently burst, resulting in the formation of large-scale and connected sand bodies dominated by river channel deposits. Guided by the above understandings, the paper establishes a hydrocarbon enrichment mode of "oil transported through Guantao Formation and retained in the gentle slope, oil migration controlled by strike-slip faults, and oil trapped in the Lower Member of Minghuazhen Formation due to channel avulsion" in the slope area of Shijiutuo uplift. The Qinhuangdao27-3 oilfield was successfully discovered in the Lower Member of Minghuazhen Formation. The key exploration technology for discriminating the connectivity of the large-scale connected sand bodies in the Neogene provides important technical support for the efficient evaluation of Qinhuangdao27-3 oilfield. The new geological understandings and key technologies formed during oilfield exploration offer a favorable reference for the exploitation of extra-source strata in the slope of Bohai Bay Basin.

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.

The enrichment theories of continental shale oil reservoirs are understudied due to its strong heterogeneity, complex microscopic oil occurrence, and unclear self-containment mechanisms. This paper is a case study of Lucaogou Formation in Jimusaer sag, Junggar Basin. Based on field emission scanning electron microscopy (FE-SEM), two-dimensional nuclear magnetic resonance (NMR), laser scanning confocal microscope (LSCM), low-temperature nitrogen adsorption experiments, and Soxhlet stepwise extraction combined with Fourier transform infrared spectroscopy (FTIR) analysis, the occurrence characteristics and self-containment mechanism of shale oil were systematically investigated. The research results show as follows. (1) Shale oil exhibits an onion skin-like occurrence model. Light components and isolated pore water occupy the centers of macropores (pore diameter greater than or equal to 2 μm), while heavy components oil occur as film-like coatings on pore surfaces. Micropores (pore diameter less than 2 μm) are filled with heavy components. (2) There are molecular-scale pores in shale oil sweet-spot reservoirs, with the minimum size ranging from 2 nm to 3 nm. (3) The microscale fluid occurrence patterns in continental shale reservoirs are governed by the factors including hydrocarbon-generating overpressure-driven micro-migration, oil-water competitive adsorption and displacement, multi-stage continuous hydrocarbon charging, and fluid-pore coupling. Shale oil accumulation involves two microscopic self-containment mechanisms based on interfacial adsorption and pore structure-fluid occurrence coupling. The depletion development of continental shale oil demonstrates gradational and staged characteristics in terms of producible pore scales and fluid components.

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.

The Permian Fengcheng Formation of Mahu sag is the main oil-yielding stratum in Junggar Basin. It deposited in a typical alkaline lacustrine environment during Early Permian. The study targets at Well X203 in the northern slope zone of Mahu sag. Through core and rock thin section observations, the lithofacies filling and association patterns in Fengcheng Formation were identified, depositional system tracts were divided into several types, and the paleo-depositional environment was reconstructed based on geochemical analysis results. Further, a sedimentary evolution model for the Fengcheng Formation was established, and the development mechanism of hydrocarbon source rocks was analyzed. The results indicate that Fengcheng Formation comprises one and a half three-order stratigraphic cycles. Specifically, a vertical succession from delta front subfacies to shallow lacustrine subfacies, and finally to semi-deep lake subfacies is developed from base to top in the transgressive systems tract (TST). The maximum flooding surface (MFS) is marked by deep-lake subfacies horizontal laminated mudstone. In the regressive systems tract (RST), a transition from semi-deep lake subfacies to shore-shallow lake subfacies occurred as the water gradually shallowed. Based on an integrated analysis of geochemical indicators including thermal evolution, redox state, salinity, and productivity, it is suggested that the lacustrine environment evolution process can be divided into three phases (P1, P2 and P3). Phase P1 refers to the initial transgression phase, in which the depositional water body exhibited relatively low salinity, followed by gradual salinization due to the hydrolysis reaction. During Phase P2, Fengcheng Formation was deposited in a suboxic aquatic environment, where the water salinity reached the highest level and the alkaline minerals were precipitated in the basin under continuous hydrolysis and arid climate. Phase P3 was characterized by a persistent decline in the relative lake level corresponding to the depositional water body in Fengcheng Formation. However, the enhanced freshwater influx driven by climate changes reduced the lake water salinity, thus forming an oxic environment. Overall, the saline and low-energy lacustrine conditions in Phase P2 promoted the proliferation of halophilic microorganisms, thus providing a basis for the formation of high-quality source rocks. Furthermore, the suboxic-anoxic conditions in relatively deep water of Phase P2 facilitated effective organic matter preservation, which is an essential prerequisite for the development of source rocks in Fengcheng Formation.

The Mianyang-Guang’an shallow-water shelf is another key area for Permian-Triassic natural gas exploration in Sichuan Basin, following the Kaijiang-Liangping trough. Currently, existing efforts mainly focus on hydrocarbon exploration in bioclastic bank development zones at the margin of Suining and Guang’an platforms on both sides of the study area, while insufficient attention has been paid to the clustered biological reefs within the shelf. In 2003, the gas testing of Permian Changxing Formation at Well Pengshen10 deployed within the shelf demonstrates a high-yield industrial gas flow of 206.36×10 ⁴m ³/d, exhibiting the promising exploration prospects of biological reefs. Through petrographic and geochemical analyses based on core samples, solid bitumen samples as well as seismic and logging data, this study systematically investigates the stratigraphic and sedimentary characteristics, hydrocarbon accumulation conditions, periods and patterns of Changxing Formation at Well Pengshen10. The research results show as follows. (1)The Changxing Formation at Well Pengshen10 is composed of the pinnacle reef subfacies of shallow-water shelf. The reef reservoir is charaterized with abundant dissolution pores and structural fractures, forming a good reservoir-cap combination with the overlying Feixianguan Formation mudstone. (2)The geochemical characteristics of solid bitumen in natural gas reservoir demonstrate the contributions of source rocks from Longtan Formation and Qiongzhusi Formation. The Pengshen10 well area has developed a deep-seated strike-slip fault that runs through the Sinian Dengying Formation and the Permian Changxing Formation, serving as a key channel for vertical oil and gas migration. The lithologic traps are primarily developed in Changxing Formation at Well Pengshen10. (3)The homogenization temperature of inclusions and the burial-thermal history of reservoirs jointly reveal that hydrocarbon charging mainly occurred in the Early Triassic and Middle to Late Jurassic. Based on this, combined with the development of faults and traps during the oil and gas charging period, a hydrocarbon accumulation model was ultimately established, involving multi-source hydrocarbon supply, fault-mediated migration, as well as oil-gas accumulation and adjustment in the lithological and structural traps. The exploration breakthrough at Well Pengshen10 reveals that it is a representative area for the large-scale hydrocarbon accumulation in biological reefs over the shallow-water shelves, which points out a new direction for the exploration and deployment of natural gas in the Permian-Triassic reef shoal reservoirs of Sichuan Basin.