This study took the Gulong Shale in the Upper Cretaceous Qingshankou Formation of the Songliao Basin, NE China, as an example. Through paleolake-level reconstruction and comprehensive analyses on types of lamina, vertical associations of lithofacies, as well as stages and controlling factors of sedimentary evolution, the cyclic changes of waters, paleoclimate, and continental clastic supply intensity in the lake basin during the deposition of the Qingshankou Formation were discussed. The impacts of lithofacies compositions/structures on oil-bearing property, the relation between reservoir performance and lithofacies compositions/structures, the differences of lithofacies in mechanical properties, and the shale oil occurrence and movability in different lithofacies were investigated. The insights of this study provide a significant guideline for evaluation of shale oil enrichment layers/zones. The non-marine shale sedimentology is expected to evolve into an interdisciplinary science on the basis of sedimentary petrology and petroleum geology, which reveals the physical, chemical and biological actions, and the distribution characteristics and evolution patterns of minerals, organic matter, pores, fluid, and phases, in the transportation, sedimentation, water-rock interaction, diagenesis and evolution processes. Such research will focus on eight aspects: lithofacies and organic matter distribution prediction under a sequence stratigraphic framework for non-marine shale strata; lithofacies paleogeography of shale strata based on the forward modeling of sedimentation; origins of non-marine shale lamina and log-based identification of lamina combinations; source of organic matter in shale and its enrichment process; non-marine shale lithofacies classification by rigid particles + plastic components + pore-fracture system; multi-field coupling organic-inorganic interaction mechanism in shale diagenesis; new methods and intelligent core technology for shale reservoir multi-scale characterization; and quantitative evaluation and intelligent analysis system of shale reservoir heterogeneity.

Traditional petroleum system theories emphasize the restoration of the accumulation process from “source” to “trap”. The main oil and gas resources in the concept are conventional oil and gas, lacking the concept and research of unconventional oil and gas enrichment mechanism. The whole petroleum system is developed from the traditional petroleum system. Combined with unconventional oil and gas exploration practices and discoveries such as shale oil and gas, the whole petroleum system adds the research content of unconventional oil and gas. Although the study of the whole petroleum system is still in three aspects: geological elements, dynamic evolution and oil and gas distribution, its research ideas and research contents are very different, including the following three aspects. (1) In terms of geological elements, the traditional petroleum system studies the characteristics of source rocks and hydrocarbon generation evolution, and the reservoir properties, traps, migration and preservation conditions of conventional oil and gas. On the basis of the above research, the whole petroleum system has increased the quantitative evaluation of retained hydrocarbons, unconventional reservoir characterization, source reservoir configuration and other research contents. (2) In terms of dynamic evolution, the petroleum system studies the matching between the evolution of conventional oil and gas source rocks and the formation period of traps, while the whole petroleum system has increased the research content of the matching of unconventional reservoir densification and oil and gas charging, and the later transformation of unconventional oil and gas reservoirs. (3) In terms of oil and gas distribution, the petroleum system takes buoyancy-drived accumulation mechanism as the core to study the migration, accumulation and distribution of conventional oil and gas. The whole petroleum system adds unconventional oil and gas self-sealing accumulation mechanism and conventional-unconventional oil and gas distribution sequence, so as to determine the oil and gas distribution characteristics of the whole petroleum system.

The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity, but the shale gas enrichment pattern is still unclear. Based on the detailed characterization of Deyang-Anyue aulacogen, analysis of its depositional environments, together with reconstruction of shale gas generation and enrichment evolution against the background of the Leshan-Longnüsi paleouplift, the aulacogen-uplift enrichment pattern was elucidated. It is revealed that the Deyang-Anyue aulacogen controls the depositional environment of the Qiongzhusi Formation, where high-quality sedimentary facies and thick strata are observed. Meanwhile, the Leshan-Longnüsi paleouplift controls the maturity evolution of the shale in the Qiongzhusi Formation, with the uplift located in a high position and exhibiting a moderate degree of thermal evolution and a high resistivity. The aulacogen-uplift overlap area is conducive to the enrichment of shale gas during the deposition, oil generation, gas generation, and oil-gas adjustment stage, which also has a joint control on the development of reservoirs, resulting in multiple reservoirs of high quality and large thickness. Based on the aulacogen-uplift enrichment pattern and combination, four types of shale gas play are identified, and the sweet spot evaluation criteria for the Qiongzhusi Formation is established. Accordingly, a sweet spot area of 8 200 km² in the aulacogen is determined, successfully guiding the deployment of Well Zi 201 with a high-yield industrial gas flow of 73.88×10⁴ m³/d. The new geological insights on the aulacogen-uplift enrichment pattern provide a significant theoretical basis for the exploration and breakthrough of deep to ultra-deep Cambrian shale gas, highlighting the promising exploration prospect in this domain.

Based on the data from 3D seismic surveys, drilling, sidewall coring, thin sections, and tests, this paper analyzes Meso-Cenozoic geotectonic dynamics, buried-hill reservoir characteristics, and differential enrichment patterns of oil and gas in the buried hills, as well as case studies of typical reservoirs, to systematically discuss the conditions required for the formation of buried-hills and reservoirs and accumulations in the large oil and gas fields in deep to ultra-deep composite buried hills in the Bohai Sea.. The key findings are as follows. First, deep to ultra-deep composite buried hills developed in the offshore Bohai Bay Basin primarily due to the double-episode destruction of the North China Craton in the Yanshanian and Himalayan. The Tanlu Fault's activity and the destruction of the North China Craton worked together to create the destruction center, which moved and converged episodically from the Bohai Bay Basin’s margins towards the Bozhong Sag. This led to the formation of two development zones for composite buried hills and an orderly process of mountain-building within the offshore Bohai Bay Basin and subsequently two development zones for composite buried hills, i.e. the middle and inner rim zones within the Bozhong Depression. Second, under the coupling of favorable lithologies and multi-stage structures, the middle and inner rim zones are favorable for the formation of reservoirs in fluid dissolution-pore/fracture zones underlying the weathering crust. Third, Massive hydrocarbons were produced along the middle and inner rim zones during the Episode II craton destruction, which caused overpressure. These hydrocarbons then moved to and accumulated in the composite buried hills. Excellent conditions for the accumulation of hydrocarbons are still present in the interior and lower portions of these buried hills. These results encourage a change in buried hill research to investigate composite buried hills in three dimensions. It should be noted that the multi-stage volcanic structures in the inner rim zone of the Sag and the deep to ultra-deep composite buried hill interiors in the middle rim zone are significant successor areas for further Bohai Sea exploration.

Based on the research progress of the geological theory of coal-formed gas, the contributions of coal-formed gas to the natural gas reserves and production in China and to the development of natural gas in major gas-producing basins are analyzed, and the key favorable exploration zones for coal-formed gas in China are comprehensively evaluated. The following results are obtained. First, coal measures are good gas source rocks, and hydrocarbon generation from coal measure was dominated by gas, followed by oil. Second, a natural gas genetic identification index system based on stable isotopes, light hydrocarbon components, and biomarkers is established. Third, the quantitative and semi-quantitative factors controlling the formation of large gas fields, represented by the indicator of gas generation intensity greater than 20×10⁸ m³/km², are identified to guide the discovery of large gas fields in China. Fourth, coal-formed gas is the major contributor to the current natural gas reserves and production of China, both accounting for over 55%. The high proportion of coal-formed gas has enabled the Tarim, Sichuan and Ordos basins to be the major gas production areas in China. Fifth, coal rock gas is an important field for future exploration of coal-formed gas, and key zones include the Carboniferous Benxi Formation (Fm.) in the Wushenqi-Mizhi area of the Ordos Basin, the Permian Longtan Fm. in central-southern Sichuan Basin, the Jurassic Xishanyao Fm. in the southern margin and Luliang uplift of the Junggar Basin. Sixth, tight gas is the main area for increasing reserves and production, and the favorable exploration zones include the Carboniferous-Permian in southern Ordos Basin and the Bohai Bay Basin, and the Triassic Xujiahe Fm. in the transition zone between central and western Sichuan Basin. Seventh, the Jurassic in the southern margin of the Junggar Basin is a key favorable exploration zone for subsequent investigation of conventional coal-formed gas. These insights have valuable theoretical and practical significance for further developing and improving the theory of coal-formed gas, and guiding the exploration of coal-formed gas fields in China.

This study integrates field outcrop profiles, drilling cores, 2D seismic profiles, and 3D seismic data of key areas to analyze the Triassic tectonic-sequence stratigraphy in the Kuqa foreland basin, and investigates the impact of episodic thrust structures on sedimentary evolution and source rock distribution. (1) The Kuqa foreland basin has experienced stages of initial strong, weakened activities, relaxation and inactivity of episodic thrusting, resulting in the identification of 4 second-order sequences (Ehebulake Formation, Karamay Formation, Huangshanjie Formation, Taliqike Formation) and 11 third-order sequences (SQ1-SQ11) in the Triassic strata. Each sequence or secondary sequence displays a “coarse at the bottom and fine at the top” pattern due to the influence of secondary episodic thrust activity. (2) The episodic thrusting is closely linked to regional sequence patterns, deposition and source rock formation and distribution. The sedimentary evolution in the Triassic progresses from fan delta to braided river delta, lake, braided river delta, and meandering river delta, corresponding to the initial strong to the inactivity stages of episodic thrusting. The development stage of thick, coarse-grained sandy conglomerate reservoirs aligns with the strong to weakened thrust activities, while the source rock formation period coincides with the relaxation to inactivity stages. (3) Controlled by the intensity and stages of episodic thrust activity, the nearly EW trending thrust fault significantly thickened the footwall source rock during the Huangshanjie Formation, becoming the development center of Triassic source rock, and experienced multiple overthrust nappes in the soft stratum of the source rock, showing “stacked style” distribution. (4) The deep layers of the Kuqa foreland basin have the foundation and conditions necessary for the formation of substantial gas reservoirs, capable of forming various types of reservoirs such as self-generating and self-storing lithology, lower generating and upper storing fault block-lithology, and stratigraphic unconformity. This area holds significant importance for future gas exploration efforts aimed at enhancing reserves and production capabilities.

Based on commercial databases from S&P Global and Rystad Energy and public information from oil companies around the world, a systematic analysis has been conducted on the global hydrocarbon exploration investment, award of exploration blocks, exploratory drilling, new conventional oil and gas discoveries, and exploration of associated resources in 2023. In 2023, the global hydrocarbon exploration investment increased steadily and the total number and area of awarded exploration blocks increased significantly. The decline in the number and success rate of high-impact exploration wells directly affected the quantity of additional oil and gas reserves discovered globally in 2023. In recent years, the deepwater areas of passive margin basins have been the major targets for seeking medium- and large-sized conventional oil and gas fields. In 2023, however, the newly discovered onshore reserves were equivalent to the newly discovered offshore reserves, and fine exploration in mature blocks achieved significant results. Oil companies continued to plan and perform unconventional oil and gas exploration activities and accelerated access to associated mineral resources such as natural hydrogen and helium and other emerging industries. For Chinese oil companies international exploration business, it is recommended to: (1) continue the upstream investment to strengthen upstream services for consolidating the strategic position of oil and gas resources; (2) uphold oil and gas exploration activities by further deploying exploration activities in the deepwater areas of passive margin basins, deeply exploring mature basins, closely following hotspot basins, and gaining access to frontier basins; (3) follow the principle of integrated development to plan the exploration of associated resources while exploiting conventional and unconventional resources; and (4) make technological innovations to develop and improve core technologies and promote the application of artificial intelligence.

Through investigating the Triassic Yanchang Formation in the Ordos Basin, black carbon has been found for the first time in the seventh member of the Middle Triassic Yanchang Formation (Chang 7 Member). This study suggests that the oxygen content in the East Tethys during the Middle Triassic was beyond 15% and that plants had recovered from the Late Permian mass extinction. The results show that the distribution of black carbon in the Chang 7 Member is heterogeneous in the basin. In the southeastern part, the black carbon content is the highest (possibly higher than 6%) in shale, with the proportion in total organic carbon content (TOC) up to 20%, which is lower than 10% in the northwestern and northeastern parts. The traditional practice needs to be re-evaluated when using TOC as a critical index in source rock evaluation and shale oil and gas sweet spot screening. Shale with high TOC may not necessarily be effective source rocks and or attractive targets for unconventional oil and gas exploitation, whereas those with low TOC could potentially be effective or high-quality source rocks. The TOC in shale can be divided into mass fractions of black carbon (w_b), active carbon (w_a), residual carbon (w_r), and carbon from mature shale oil (w_o). TOC-w_b is recommended for evaluation of source rock, w_a for screening the in-situ recovery area of low to medium maturity shale oil, and w_o for appraisal of the favorable exploration area of medium to high mature shale oil. These results allow for the quantitative evaluation of organic matter composition of shale, hydrocarbon generation potential, maturation stage, and generation, expulsion and retention of shale oil, and also guide the reconstruction of climate in the source rock development period and the shale oil and gas sweet spot screening.

The depositional facies types of the fourth member of the Middle Triassic Leokoupo Formation (Lei-4 Member) in western Sichuan Basin are examined through the methods of sedimentology, lithology and analysis of well-logging data, as well as the special lithofacies indicators such as microbialite, gypsum-salt rock and tempestites, using the data of about 400 wells and 11 outcrop sections. The distribution and evolution and its hydrocarbon geological significances of the bay facies have been discussed. The Lei-4 Member in western Sichuan Basin has an ocean-bay-flat depositional model, with the presence of evaporated tidal flat, restricted tidal flat and paleo-bay facies from east to west. The subfacies such as bay margin, subtidal bay and bay slope are recognized within the paleo-bay, with microbial reef and grain bank microfacies in the bay margin, microbial flat, deep-water spongy reef and hydrostatic mudstone microfacies in the subtidal bay, and tempestites and collapsed deposits in the upper bay slope. The bay boundary covered the Guangyuan-Zitong-Dujiangyan area in the period of the first submember of the Lei-4 Member (Lei-4-1) with falling sea level, regressed westward into the Shangsi-Jiangyou-Dujiangyan area in the period of Lei-4-2, and expanded to the Shangsi-Zitong-Langzhong- Wusheng-Yanting-Chengdu area in the northern part of central Sichuan Basin in the period of Lei-4-3 along with a small-scale transgression. The topographic pattern of “one high and two lows” is confirmed in the Lei-4 Member, corresponding to a configuration of source rocks and reservoir rocks alternated horizontally and superimposed vertically. Two efficient source-reservoir configuration models, i.e. side source & side reservoir, and self-generating & self-storing, are available with the microbial reef and grain bank reservoirs at the bay margin and the high-quality source rocks within the sags on both sides of the bay. The research findings will inevitably open up a new situation for the hydrocarbon exploration in the Leikoupo Formation.

The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms. The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan Formation (N₁-N₂¹) in the Fengxi area Qaidam Basin, were investigated through core-log and petrology-geochemistry cross-analysis by using the core, casting thin section, scanning electron microscope, X-ray diffraction, logging, and carbon/oxygen isotopic data. The hybrid sedimentary rocks in the Fengxi area, including terrigenous clastic rock and lacustrine carbonate rock, were deposited in a shallow lake environment far from the source, or occasionally in a semi-deep lake environment, with 5 lithofacies types and 6 microfacies types recognized. Stable carbon and oxygen isotopic compositions reveal that the formation of sedimentary cycles is controlled by a climate-driven compensation-undercompensation cyclic mechanism. A sedimentary cycle model of hybrid sedimentary rocks in an arid and saline setting is proposed. According to this model, in the compensation period, the lake level rises sharply, and microfacies such as mud flat, sand-mud flat and beach are developed, with physical subsidence as the dominant sedimentary mechanism; in the undercompensation period, the lake level falls slowly, and microfacies such as lime-mud flat, lime-dolomite flat and algal mound/mat are developed, with chemical-biological process as the dominant sedimentary mechanism. In the saline lacustrine sedimentary system, lacustrine carbonate rock is mainly formed along with regression, the facies change is not interpreted by the accommodation believed traditionally, but controlled by the temporary fluctuation of lake water chemistry caused by climate change. The research results update the interpreted high-resolution sequence model and genesis of hybrid sedimentary rocks in the saline lacustrine basin and provide a valuable guidance for exploring unconventional hydrocarbons of saline lacustrine facies.

Based on 2D and 3D seismic data and well logging data, this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope of Leshan-Longnüsi paleouplift in the Sichuan Basin, to reveal the genetic relationship between stratigraphic filling, paleogeomorphology and large-scale grain shoal. (1) The Xixiangchi Formation in the study area is overlapped and filled gradually to the Leshan-Longnüsi paleouplift, but gets thin sharply due to truncation only near the denudation pinch-out line of the paleouplift. Two overlap slope break belts and one erosion slope break belt are identified, and the Xixiangchi Formation is divided into 4 members from bottom to top. (2) The filling pattern of the overlapping at the base and erosion at the top indicates that the thickness of Xixiangchi Formation can reflect the pre-depositional paleogeomorphology, and reveals that the studied area has a monoclinal geomorphic feature of plunging to southeast and being controlled by multistage slope break belts. (3) The large-scale grain shoals and shoal controlled reservoirs are developed longitudinally in the third and fourth members of the Xixiangchi Formation, and laterally in the vicinity of the multistage overlap slope break belts. (4) Overlap slope break belts are closely related to northwest trending reverse faults. The western margin of the South China Plate converging with the Qiangtang-Himalaya massif in the middle -late Cambrian resulted in the rapid uplift of the northwestern margin of the Yangtze Plate and expanding toward southeast, leaving gradually plunging multistage slope breaks and large-scale northeast grain shoal reservoir belts. Considering oil and gas test results, it is predicted that the favorable exploration zone of the grain shoal controlled reservoirs covers an area of 3 340 km².

This paper presents an analysis of four aspects, including the distribution and production of global oil and gas fields, the distribution and changes of remaining recoverable reserves, the differences in oil and gas production between regions/countries, and the development potentials of oil and gas fields unproduced and to be produced in 2023. On this basis, the situation and characteristics of global oil and gas development are expounded, and the trend of global oil and gas development is summarized. In 2023, upstream oil and gas production landscape is expanding, and the number of oil and gas fields in production is increasing significantly; oil and gas recoverable reserves increased year-on-year, driven by significant contributions from new discoveries and reserve re-estimates; the overall oil and gas production grew continuously, with notable contributions from new projects coming online and capacity expansion efforts; and the oil and gas fields unproduced or to be produced, especially large onshore conventional oil fields and economically challenging offshore gas fields, host abundant recoverable reserves. From the perspectives of reshaping oil and gas production areas due to the pandemic and Russia-Ukraine conflicts, geopolitical crises, capital expenditure structures in petroleum exploration and development, and the proactive layout of oil and gas associated resources, the trend of global oil and gas development in 2023 was analyzed systematically. The enlightenment and suggestions in four aspects are proposed for Chinese oil companies to focus on core businesses and clarify development strategies in the post-pandemic era and the context of energy transition: The global oil and gas landscape is undergoing profound adjustments, and it is essential to grasp development trends, especially in core businesses; upstream business exhibits a strong potential, and emerging fields are considered as new growth poles; the prospects for tight/shale oil and gas are promising, and new pathways to ensure national energy security are explored; cutting-edge breakthroughs are achieved in emerging industries of strategic importance, and a comprehensive energy collaboration system for supply security is established.

The high temperature and high pressure visualization pressure-volume-temperature (PVT) experiments of different gas media-crude oil were carried using the interface disappearance method. There are two miscible temperature domains in the miscibility of CO₂-crude oil during heating process under constant pressure. Under the experiment pressure of 15 MPa, when the temperature is less than 140 °C, the miscible zone shows liquid phase characteristics, and increasing the temperature inhibits the miscible process; when the temperature is greater than 230 °C, the miscible zone tends to show gas phase characteristics, and increasing the temperature is conducive to the miscibility formation. Under a certain pressure, with the increase of temperature, the miscibility of flue gas, nitrogen and crude oil is realized. When the temperature is low, the effect of CO₂ on promoting miscibility is obvious, and the order of miscible temperature of gas medium and crude oil is N₂ > flue gas > CO₂; however, when the temperature is high, the effect of CO₂ on promoting miscibility gradually decreases, and the miscible temperature of N₂ and crude oil is close to that of flue gas. The miscibility is dominated by the distillation and volatilization of light components of crude oil. There are many light hydrocarbon components in the gas phase at phase equilibrium, and the miscible zone is characterized by gas phase.

Considering the adsorption loss of the hydraulic fracturing assisted oil displacement (HFAD) agent in the matrix, a method is proposed to characterize the dynamic saturation adsorption capacity of the HFAD agent with pressure differential and permeability. Coupled with the viscosity-concentration relationship of the HFAD agent, a non-linear seepage model of HFAD was established, taking into account the adsorption effect of high pressure drops, and the influencing factors were analyzed. The findings indicate that the replenishment of formation energy associated with HFAD technology is predominantly influenced by matrix permeability, fracture length and the initial concentration of the HFAD agent. The effect of replenishment of formation energy is positively correlated with matrix permeability and fracture length, and negatively correlated with the initial concentration of the HFAD agent. The initial concentration and injection amount of the high-pressure HFAD agent can enhance the concentration of the HFAD agent in the matrix and improve the efficiency of oil washing. However, a longer fracture is not conducive to maintaining the high concentration of the HFAD agent in the matrix. Furthermore, the fracture length and pump displacement are the direct factors affecting the fluid flow velocity in the matrix subsequent to HFAD. These factors can be utilized to control the location of the displacement phase front, and thus affect the swept area of HFAD. A reasonable selection of the aforementioned parameters can effectively supplement the formation energy, expand the swept volume of the HFAD agent, improve the recovery efficiency of HFAD, and reduce the development cost.

Two etching models, the spherical-rod standard pore channel and the pore structure, were used to conduct displacement experiments in the water-gas dispersion system to observe the morphological changes and movement characteristics of microbubbles. Additionally, numerical simulation methods were employed for quantitative analysis of experimental phenomena and oil displacement mechanisms. In the experiment, it was observed that microbubble clusters can disrupt the pressure equilibrium state of fluids within the transverse pores, and enhancing the overall fluid flow; bubbles exhibit a unique expansion-contraction vibration phenomenon during the flow process, which is unobservable in water flooding and gas flooding processes. Bubble vibration can accelerate the adsorption and expansion of oil droplets, and promote the emulsification of crude oil, thereby improving microscopic oil displacement efficiency. Combining experimental data with numerical simulation analysis of bubble vibration effects, it was found that microbubble vibrations exhibit characteristics of a sine function, and the energy release process follows an exponential decay pattern; compared to the gas drive front interface, microbubbles exhibit a significant “rigidity” characteristic; the energy released by microbubble vibrations alters the stability of the seepage flow field, resulting in significant changes to the flow lines; during the oil displacement process, the vast number of microbubbles can fully exert their vibrational effects, facilitating the migration of residual oil and validating the mechanism of the water-gas dispersion system enhancing microscopic oil displacement efficiency.

The thermal flux curve of phase-transition fluid (PF) was tested using differential scanning calorimetry, based on which a reaction kinetics model was established to reflect the relationship between phase transition conversion rate, temperature and time. A temperature field model for fractures and rock matrix considering phase transition heat was then constructed, and its reliability was verified using previously established temperature field models. Additionally, the new model was used to study the effects of different injection parameters and phase-transition fracturing performance parameters on the temperature variations in fractures and matrix. The study indicates that, at different positions and times, the cooling effect of the injected cold fluid and the exothermic effect during the phase transition alternately dominate the temperature within the fracture. At the initial stage of fracturing fluid injection, the temperature within the fracture is high, and the phase transition rate is rapid, resulting in a significant impact of exothermic phase transition on the reservoir rock temperature. In the later stage of injection, the fracture temperature decreases, the phase transition exothermic rate slows, and the cooling effect of the fracturing fluid on the reservoir rock intensifies. Phase transition heat significantly affects the temperature of the fracture. Compared to cases where phase transition heat is not considered, when it is taken into account, the temperature within the fracture increases to varying degrees at the end of fluid injection. As the phase transition heat increases from 20 J/g to 60 J/g, the maximum temperature rise in the fracture increases from 2.1 °C to 6.2 °C. The phase transition heat and PF volume fraction are positively correlated with fracture temperature changes, while specific heat capacity is negatively correlated with temperature changes. With increasing injection time, the temperature and phase transition rate at the fracture opening gradually decrease, and the location of the maximum phase transition rate and temperature difference gradually shifts from the fracture opening to about 10 m from the opening.

By considering the thermo poroelastic effects of rock, the constitutive relationship of fatigue deterioration of rock under cyclic loading, elastic-brittle failure criteria and wellbore stress superposition effects, a thermal-hydraulic-mechanical- fatigue damage coupled model for fracture propagation during soft hydraulic fracturing in hot dry rock (HDR) was established and validated. Based on this model, numerical simulations were conducted to investigate the fracture initiation and propagation characteristics in HDR under the combined effects of different temperatures and cyclic loading. The results are obtained in three aspects. First, cyclic injection, fluid infiltration, pore pressure accumulation, and rock strength deterioration collectively induce fatigue damage of rocks during soft hydraulic fracturing. Second, the fracture propagation pattern of soft hydraulic fracturing in HDR is jointly controlled by temperature difference and cyclic loading. A larger temperature difference generates stronger thermal stress, facilitating the formation of complex fracture networks. As cyclic loading decreases, the influence range of thermal stress expands. When the cyclic loading is 90%p_b and 80%p_b (where p_b is the breakdown pressure during conventional hydraulic fracturing), the stimulated reservoir area increases by 88.33% and 120%, respectively, compared to conventional hydraulic fracturing (with an injection temperature of 25 °C). Third, as cyclic loading is further reduced, the reservoir stimulation efficiency diminishes. When the cyclic loading decreases to 70%p_b, the fluid pressure far away from the wellbore cannot reach the minimum breakdown pressure of the rock, resulting in no macroscopic hydraulic fractures.

Considering the demands, situations and trends in respect to global climate change, carbon neutrality and energy transition, the achievements and significance of the global green energy transition and the new energy revolution of China are summarized, and the “Energy Triangle” theory is proposed. The research indicates that the energy technology revolution is driving a dual transformation in global energy: the black “shale oil and gas revolution” in North America and the green “new energy revolution” in China. The green energy revolution of China has achieved significant milestones in wind-solar-hydrogen-energy storage technologies, leading the world in photovoltaic and wind power. The country has developed the world’s largest, most comprehensive, and competitive new energy innovation, industrial and value chains, along with the largest clean power supply system globally. New quality productive forces represent the green productive forces. The green “new energy revolution” of China has accelerated the transformation of its energy structure and the global shift towards clean energy, promoting a new win-win model for the global green and low-carbon transition. Under the backdrop of a carbon-neutral goal-driven energy transition, the “Energy Triangle” theory within the framework of new quality productive forces explains the correlation and development of energy security, economic growth, and environmental sustainability throughout the evolution from fossil fuels to new energy systems, culminating in an energy revolution. Compared to the global energy resource endowment, the energy resources of China are characterized by abundant coal, limited oil and gas, and unlimited wind and photovoltaic energy. Moving forward, the energy strategies of China will focus on the advancement of technologies to clean coal for carbon emission reduction, increase gas output while stabilizing oil production, increase green energy while enhancing new energy, and achieve intelligent integration. Vigorously developing new energy is an essential step in maintaining the energy security of China, and establishing a carbon-neutral “super energy system” is a necessary choice. It is crucial to enhance the international competitiveness of China in new energy development, promote high-quality energy productive forces, support the country’s transition to an “energy power”, and strive for “energy independence”.

Taking the Ordos Basin as an example, this paper proposed that the construction of an energy super basin should follow the principle of “more energy, less carbon, and better energy structure”. The modeling workflow of energy super basin was built. Based on the resources/reserves, development status and infrastructures of the Ordos Basin, the development potential of the basin was evaluated, the uncertainties in the construction of energy super basin were analyzed, and the future vision and realization path of the Ordos Energy Super Basin were recommended. This study demonstrates that the Ordos Basin has the advantages of abundant energy sources, perfect infrastructures, well-matched carbon source and sink, small population density, and proximity to the energy consumption areas. These characteristics ensure that the Ordos Basin is a good candidate of the energy super basin. It is expected that the energy supply of the Ordos Basin in 2050 will reach 23×10⁸ t of standard coal, and the proportion of fossil fuels in energy supply will decrease to 41%. The carbon emissions will decrease by 20×10⁸ t compared to the emissions in 2023. The future construction of the basin should focus on the generation and storage of renewable energy, and technological breakthroughs for the carbon capture, utilization and storage.