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 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.

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.

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.

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.

Hydraulic fracturing in unconventional reservoir is currently challenged by limited understanding of the spatial configuration of fracture networks and the effectiveness of proppant placement. To address these issues, Changqing oilfield has taken the lead in establishing the Qingcheng shale oil hydraulic fracturing test site (HFTS), the first of its kind in China. This study outlines the coring procedure and develops a set of criteria for fracture characterization based on fracture surface morphology. Fractures are primarily categorized into bedding fractures, structural fractures, hydraulic fractures, and drilling-induced fractures. Two approaches are proposed for proppant identification, i.e., analyzing drilling cuttings for the presence of proppant during the mud logging stage, and identifying proppant residues or imprints on fracture surfaces during core observation. A total of 661 meters of cores were retrieved from HFTS, revealing 767 fractures, of which 326 were identified as being hydraulically induced. A total of 27 pieces of proppant residues or imprints were observed on fracture surfaces, and proppant particles were commonly detected in the drilling cuttings. In terms of spatial distribution, hydraulic fractures exhibit the half-lengths of up to 220 meters and heights reaching 66.6 meters. Proppant was detected within induced fractures in the coring well located as far as 175 meters from the fractured well and up to 49.3 meters in height; however, the overall proppant concentration remained relatively low. Fractures predominantly display parallel, banded, and clustered spatial patterns, characterized by relatively low complexity and insufficient reservoir coverage.

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.

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.

Tar-rich coal is a strategically important unconventional hydrocarbon resource in China, and the study of its formation mechanisms and exploitation potential plays a pivotal role in national energy transition. Through systematically analyzing the geological characteristics and genetic mechanisms of major tar-rich coal basins in China, it has been found that tar yield is controlled by the coupled effects of multiple factors. Tar-rich coals were predominantly developed in the Ordos, Junggar, Turpan-Hami, and Santanghu basins from the Paleozoic to the Mesozoic, especially in the Jurassic. Research demonstrates that tar-rich coal is predominantly composed of vitrinite, characterized with ultra-low to medium moisture and ash contents, ultra-low to medium sulfur content, medium-high to high volatile matter, and significant variations in tar yield. It exhibits the following petrographic characteristics: vitrinite content ranging from 30.10 % to 82.99 %, inertinite from 15.38 % to 66.53 %, liptinite from 0.77 % to 4.20 %, and tar yields varying between 4.39 % and 14.58 % (peaking at 22.80 %). Moreover, it shows the following coal quality characteristics: moisture content ranging from 2.82 % to 11.47 %, ash content from 8.59 % to 22.40 %, total sulfur content from 0.33 % to 1.31 %, and volatile matter content from 33.12 % to 46.14 %. In China, a majority of tar-rich coals contain Type Ⅲ ₁ kerogen derived mainly from woody and herbaceous plants, with minor contributions from aquatic plants and lower algae. The tar yield is primarily determined by several key factors, including the content of hydrogen-rich vitrinite, types of coal-forming plants, coal molecular structure, thermal maturity of organic matter, and sedimentary environment. For coals with similar ranks, variations in tar yield essentially result from the dynamic changes in organic molecular structures with the increase of thermal evolution degree, which is specifically manifested at the molecular level as the dynamic evolution of hydrogen-rich and oxygen-containing functional groups. In terms of sedimentary environments, tar-rich coals are predominantly developed in the reservoirs of delta plain subfacies and shore/shallow lacustrine subfacies, and the shallow-water environment characterized with weak hydrodynamics and low salinity is most conductive to high tar yields. It is predicted that the tar-rich coals at depths less than 2 000 m in Santanghu Basin, Turpan Basin, Hami Basin and Ordos Basin amount to over 250 billion tons. Among these, two key sweet spots have been identified, i.e., the Jurassic reservoirs in northern Shaanxi region of Ordos Basin, with 124.26 billion tons of tar resources and the Santanghu Basin. To overcome the current bottlenecks in tar-rich coal development, the study proposes a geology-engineering integration model that combines multi-index oil potential assessment with multi-field coupled pyrolysis simulation for precisely locating in-situ pyrolysis targets. These findings provide both the scientific framework and technical approach for low-carbon utilization of tar-rich coal resources, which is of strategic significance for facilitating the transition of coal from fuels to chemical feedstocks.

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.

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.

The Permian basin-scale unconformity in the northern truncation zone of Shawan sag of Junggar Basin develops between the Shangwuerhe Formation and the underlying strata, exhibiting an erosional unconformity contact. The Fengcheng Formation, Xiazijie Formation, and Xiawuerhe Formation exhibit good hydrocarbon shows in this region. Recently, a new breakthrough has been made in exploration of Well TT1 in the lowstand system tract conglomerate reservoirs of the Shangwuerhe Formation. To further summarize the Permian hydrocarbon accumulation regularities in Shawan sag, a systematic study on reservoir characteristics, sedimentary facies, and controlling factors was conducted, leading to the following conclusions. (1)The angular unconformity at the bottom of the Shangwuerhe Formation in Shawan sag controls oil and gas enrichment. The Shangwuerhe Formation possesses favorable conditions for large-scale accumulation and serves as the main target for large-scale cost-efficient exploration. (2)The Zhongguai fan provenance is abundant and the scale is large, with the development of effective reservoirs at its distal end. In the Shangwuerhe Formation retrogradational fan delta depositional system, the thin sandstone layer from the Member 2 of Shangwuerhe Formation and the sandstone body from the Member zero of Shangwuerhe Formation constitute the main reservoir bodies. (3)A Permian accumulation model characterized with "unconformity-controlled migration, anticline-controlled enrichment, and overpressure sealing" was established in the northern truncation zone of Shawan sag. The oil-over-gas distribution pattern is the result of the dynamic coupling between petroleum migration and overpressure sealing systems. The discovery of the lowstand system tract conglomerate oil reservoirs in the Shangwuerhe Formation of Well TT1 not only marks a new exploration idea of "prospecting sandstone beneath mud", but also provides valuable insights for expanding exploration fields and optimizing exploration strategies in Shawan sag.

The self-sealing capacity of shale is a critical factor for the enrichment and accumulation of shale oil and gas. However, the current understanding of the self-sealing mechanism of shale oil and gas reservoirs remains insufficient, which severely restricts the development of unconventional oil and gas geology theories and the advancement of hydrocarbon exploration in China. An in-depth research on the self-sealing mechanisms and differences regarding typical marine shale gas will contribute to improving the unconventional hydrocarbon accumulation theories and guiding the exploration and development practice. This study focuses on the Longmaxi Formation shale in Sichuan Basin, and comprehensively using petroleum geology theory, nanoscale water film theory, and adsorption thermodynamics theory, as well as gas reservoir analysis, fine-scale reservoir characterization and theoretical calculations, the following three research achievements have been obtained. (1)This study clarifies the geological characteristics of the self-sealing system of Longmaxi Formation shale gas in Sichuan Basin, discovers the vertical variation patterns and differences in the total organic carbon (TOC)content, pore structure, and fluid characteristics of the shale. These factors serve as important geological foundations for the formation of the shale gas self-sealing system. (2)The study reveals the microscopic self-sealing mechanism in shale gas reservoirs. The tight shale reservoirs with poor pore connectivity facilitate physical self-sealing. The complex organic-inorganic pore system of shale, along with its gas-water distribution patterns, jointly contribute to the capillary force-driven self-sealing effect. This effect is dually controlled by pore structure and water saturation. Moreover, the adsorption capacity of shale can result in self-sealing capacity, which is primarily related to the specific surface area and TOC content of the shale, and is particularly remarkable in organic-rich shale. (3)An analysis has been performed on the vertical differences in self-sealing effects. The upper gas reservoir is dominated by capillary force-driven self-sealing, followed by physical self-sealing. In contrast, the lower gas reservoir exhibits a composite mechanism involving physical self-sealing, capillary force-driven self-sealing, and adsorption force-driven self-sealing. The research results are expected to provide valuable insights for improving the theoretical system of unconventional oil and gas accumulation, and guiding exploration and development practices.

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.

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 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.

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.

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.

Shale oil has become an important alternative resource for oil and gas in China. Scientifically objective grading assessment of shale oil resources can provide technical support and a reference basis for oil and gas exploration and commercial hydrocarbon development. The key to shale oil resource assessment is the determination of oil content. There are numerous commonly used methods for evaluating oil content; however, due to the significant differences in geological conditions of continental basins, the assessment results are subject to uncertainty. Based on a systematic review of the methods and models for evaluating oil content in lacustrine shale, the advantages and disadvantages of various oil content assessment methods are discussed. Furthermore, based on the existing research findings, the paper proposes a new shale oil resource grading assessment model, which comprehensively considers the dynamic coupling between oil content, mobility, and geological parameters. The research results show as follows. (1) The new model uses free hydrocarbon content ( S ₁), total organic carbon (TOC) content, and the ratio of S ₁ to TOC content as grading parameters, dividing the resources into four categories, i.e., enriched resources, moderately enriched resources, low-efficiency resources, and ineffective resources. (2) The envelope curve of S ₁ variation with TOC content in typical shale basins exhibits a normal distribution pattern. When TOC content is too low or too high, the enrichment degree of shale oil resources is controlled by the source rock quality and reservoir properties, respectively. (3) In the Permian Fencheng Formation of Mahu sag in Junggar Basin and the Cretaceous Qingshankou Formation of Qijia-Gulong sag in Songliao Basin, the upper and lower limits of TOC contents in their respective shale oil enrichment areas are 0.4 % and 2.2 %, and 1.5 % and 3.4 %, with the favorable shale oil areas distributed in a circumferential pattern around the hydrocarbon generation centers. The advantages of the new model lie in: (1) considering the influences of source rock quality, reservoir properties, and their coupling relationship at the basin scale on shale oil enrichment; (2) being able to characterize the degree of shale oil resource enrichment from two perspectives, i.e., shale oil content and mobility. The model corrects the misconception that oil content remains constant after TOC content reaches a certain value, providing a basis for scientifically evaluating shale oil resources.