The development of coalbed methane (CBM) helps to achieve the goal of peak carbon and carbon neutrality as early as possible, and the industrialization of CBM development has basically been achieved in China. However, restricted by theoretical and technological factors, the development scale does not match the abundant resources. Since the 14^th Five-Year Plan period, new progress has been made in CBM exploration and development, including five aspects: (1) The large-scale development of deep CBM has begun in China, and the growth rate of CBM output has significantly accelerated; (2) Major breakthrough has been made the exploration and development of deep CBM, greatly expanding the space for industrial development; (3) Remarkable results have been achieved in reservoir stimulation and reconstruction of difficult to recover resources such as low-efficiency areas and thin coal seams in mature gas fields; (4) Compared with the 13^th Five-Year Plan period, the research focus has shifted from medium-shallow to deep CBM, great innovations have been made in CBM development theory and technology represented by large-scale horizontal well multi-stage fracturing technology in four aspects of geological understanding, drilling and completion, fracturing, and drainage and production, significantly increasing the gas production; (5) The policy environment of CBM industry has continuously been optimized. The preliminary study shows that China has abundant deep CBM resources, and deep CBM resources with a burial depth of greater than 1500 m are more than twice as those with a burial depth of small than 1500 m; The proven CBM reserves in China are dominated by middle-shallow CBM, but the recovery rate is only 7%, indicating considerable remaining resources. In addition, there are abundant CBM resources in thin coal seams in the mature gas fields, which are the realistic replacement resources. Therefore, the major breakthrough of deep CBM and the successful reservoir stimulation and reconstruction in mature gas fields have become the main driving force leading the rapid development of CBM industry, which have shown promising prospects. Based on the research results by several institutions and experts, it is expected that CBM output in China will reach 100×10⁸ m³ in 2025 and 300×10⁸ m³ in 2035. On the other hand, CBM development in China is faced with many challenges. For example, the geological theory and understanding in the new fields of deep CBM and thin coal seams need to be deeply and systematically studied, exploration and development engineering technology for deep CBM is still in the research stage, and the policy support for industrial development still needs improvement. Therefore, it is suggested to strengthen risk CBM exploration and favorable zone selection and evaluation in new fields, strengthen theoretical and technical research on high-efficiency CBM exploration and development, and strengthen policy support and development guidance for CBM industry.

A systematic review is conducted on the high-quality exploration activities, theoretical and technological progress, and exploration achievements of Sinopec during the 14^th Five-Year Plan period, and a development strategy is proposed for the future petroleum exploration. Since the 14^th Five-Year Plan period, Sinopec has strengthened its confidence in resource development and vigorously promoted high-quality exploration practices, which support to make significant exploration achievements in fields such as deep carbonate rocks, continental shale oil, deep shale gas, clastic rocks in western regions, subtle oil and gas reservoirs in mature exploration areas, and deep CBM in Tarim, Sichuan, Bohai Bay, Junggar, and Ordos basins, solidifying reserve basis for stable oil output growth and rapid gas output growth. In addition, significant progress has been made in the development and improvement of deep strike-slip fault-controlled fracture-cavity type hydrocarbon accumulation theory, the innovative shale oil reservoir formation, hydrocarbon accumulation and enrichment theory, and the deep understanding of “dual enrichment” of marine shale gas and differential enrichment mechanisms of oil and gas reservoirs in tight clastic rocks. Furthermore, the key exploration and engineering technologies for targets with complex geological and reservoir structural conditions, represented by seismic exploration, well drilling and completion in deep to ultra-deep formations, wireline logging, mud logging and well testing in ultra-deep formation, and horizontal well fracturing, have been researched and developed. Looking ahead, Sinopec has a solid resource foundation in its exploration areas for achieving steady oil output and rapid increase in gas production. The exploration work will focus on three core responsibilities of securing and expanding mining rights areas, achieving exploration breakthroughs, and increasing reserves and resources on a large scale. Guided by deep earth engineering, shale oil and gas demonstration projects, benefit development of tight clastic rock oil and gas reservoirs, and coordination of conventional and unconventional resources, efforts will be strengthened to accelerate the strategic breakthroughs, and establish large-scale reserve increase bases, so as to further consolidate resource foundation for the sustainable development of the upstream.

In order to achieve the rapid development of natural gas industry and increase gas production, CNOOC has gradually increased exploration investment in mining rights areas in Ordos Basin and Qinshui Basin, in which there are multiple types of natural gas including tight gas, CBM, and conventional gas, with gas resources of up to 3×10¹²m³ in the two basins and proven gas geological reserves of 7500×10⁸m³ in high-abundance and structurally simple zones. Based on a comprehensive analysis of resource potential and quality, gas accumulation conditions, and exploration technology, CNOOC has proposed a development strategy of increasing onshore natural gas reserves with a level of trillion cubic meters. The company has clarified the guiding ideology of simultaneous exploration of tight gas and CBM and stereoscopic exploration of multi type gas resources, and determined the deployment strategy of accelerating the exploration of deep CBM and tight gas in the eastern part of Ordos Basin and rapidly promoting the exploration of middle and shallow CBM in Qinshui Basin. Furthermore, the comprehensive analysis of exploration fields, gas accumulation and enrichment laws, and exploration technology research directions enables to clarify the key exploration orientations in the near future. The eastern Ordos Basin is characterized by orderly co-occurrence of full oil and gas system in coal measure strata. As a result, it is necessary to conduct exploration in the full gas accumulation system in coal measure strata, consolidate the material basis for increasing reserves and production, focus on tight gas and deep coalbed methane, research on CBM in thin cool seams, Ordovician conventional natural gas, and bauxite rock gas, and promote the simultaneous exploration and replacement of multi type gas resources by applying exploration and development integration and geology and engineering integration, so as to achieve the exploration and development of full gas accumulation system. In the northern and southern parts of Qinshui Basin, it is necessary to promote the volume fracturing of horizontal wells and production technology tests for middle and shallow CBM and popularize its application, and form complementary economic and effective development with thin CBM, so as to promote the overall increase in CBM reserves and production in Qinshui Basin. The exploration activities in the above key areas will ensure the reserve increase and healthy and stable development of large onshore gas region of CNOOC with a level of trillion cubic meters.

The petroleum exploration in Junggar Basin has entered a new stage of exploration in hydrocarbon rich sags, which faces new challenges such as increasing burial depth, more scattered and subtle exploration targets, poorer reservoir porosity and permeability, and low upgrade rate and recovery rate of reserves. It is an urgent task to improve exploration effectiveness and achieve benefit development of oil fields. The new round of integrated research and re-understanding of the basin indicates that the spatial distribution of multiple source kitchens in Junggar Basin are complementary, showing “abundant oil and rich gas”, which has broken through the traditional understanding of “abundant oil but less gas” in the basin; There are four types of large-scale effective reservoirs in hydrocarbon rich sags, with orderly distribution in lateral and superposition in vertical direction; Three types of hydrocarbon accumulation systems are identified, such as orderly accumulation of conventional and unconventional oil and gas in source rock, large-scale hydrocarbon accumulation in regressive fan delta facies glutenites above source rock, and stereoscopic hydrocarbon accumulation in medium-shallow fault-sand coupling reservoirs. In combination with the resource characteristics, new geological knowledge, adaptability of exploration and development technologies, and goal of sustainable and benefit development in Junggar Basin, strategies for high-efficiency exploration are proposed, including “simultaneous exploration of oil and gas, emphasis on both conventional and unconventional oil and gas, co-exploration of deep and shallow oil and gas, and reserve increase in multiple fields”, and three major exploration orientations and nine major exploration fields are put forward, so as to support the benefit and sustainable development of the oilfield.

The Permian shale gas in Sichuan Basin shows good hydrocarbon accumulation conditions and exploration potential. After obtaining breakthrough in the Permian Wujiaping Formation, the “high lime content” shale gas in Maokou Formation with a low degree of exploration has been regarded as a major orientation for exploration and replacement. The core samples, wireline and mud logging and experimental data in Well HYM-1 are used to systematically analyze the shale gas accumulation conditions and enrichment characteristics in Maokou Formation, and the study results indicate that the shale in the first sub-member of the fourth member of Maokou Formation has the typical geological characteristics of “five highs, one thin and one multiple”, i.e., high carbon content, high lime content, high porosity, high gas content, high Yong’s modulus, thin reservoirs, and multiple interbeds; Compared with the shale in Wufeng-Longmaxi Formation, Maokou Formation shale has a higher carbonate mineral content but a lower clay content, and the reservoir space is dominated by organic pores, with few inorganic pores, and an average porosity of 4.27%, showing high porosity as a whole; The average gas content of the first sub-member of the fourth member of Maokou Formation is 4.96m³/t, which shows a high gas content. The comprehensive analysis indicates that the development of algal-rich and high-carbon shale, good storage capacity and preservation conditions, as well as the good fracability of shale reservoir are the main controlling factors for the enrichment and high-yield production of shale gas in the fourth member of Maokou Formation.

The Eastern Sag of Liaohe Depression is one of the areas with the earliest biogas discoveries in China. The shallow biogas has not attracted much attention in the early exploration stage due to the good exploration results in the middle and deep formations, and there is a lack of understanding of source rocks and distribution law of shallow biogas. The geochemical characteristics of shallow gas (reservoir) in drilled wells are systematically analyzed, and a key index of carbon isotope is used to classify shallow gas (reservoir) in Eastern Sag into four types, including primary biogas, bio-transitional zone gas, transformed biogas and mixed type gas. Furthermore, the genesis of shallow gas is discussed, and it is indicated that the shallow biogas is dominated by coal measure genesis. The in-depth study supports to obtain geological understanding that the distribution of shallow biogas was distinctly controlled by coal measure strata, high-quality clastic rock reservoirs, two sets of regional cap rocks in the upper sub-member of the third member of Shahejie Formation (Es₃¹) and the first member of Shahejie Formation (Es₁), and the late formation of structures and late gas charging were conducive to the large-scale gas enrichment in shallow formations. Guided by the above understanding, high-yield gas wells and large-scale reserves have been discovered, opening up a new exploration field of coal measure genetic biogas in Liaohe Depression.

The shallow Neogene Guantao-Minghuazhen Formations are the main hydrocarbon-bearing series in Bohai Sea. The Neotectonic movements in the late Cenozoic were the most profound tectonic events in Bohai Sea, which had much greater influence on hydrocarbon accumulation in shallow formations than that in deep formations, and controlled the ultimate hydrocarbon accumulation in shallow formations. The study results show that the Neotectonic movements resulted in the rapid hydrocarbon generation and expulsion in the late sag subsidence period, development of various types of traps, and active hydrocarbon migration, which adjusted and controlled the ultimate hydrocarbon accumulation and determined the distribution of shallow oil and gas reservoirs in Bohai Sea. However, the control effect of the Neotectonic movements on hydrocarbon accumulation in shallow formations varied in various structural belts. Based on the structural position and hydrocarbon accumulation characteristics, shallow oil and gas reservoirs are classified into two major categories, i.e., shallow oil and gas reservoirs in bulge area, and shallow oil and gas reservoirs in the slope-subsag area. By analyzing hydrocarbon accumulation characteristics of shallow oil and gas reservoirs in these two structural belts, the control effect of the Neotectonic movements on the ultimate hydrocarbon accumulation and enrichment patterns of shallow oil and gas reservoirs in different structural belts are identified, and the corresponding hydrocarbon accumulation patterns are established. Among them, the hydrocarbon accumulation in shallow bulge area is characterized by a “stepped” pattern controlled by “late fault connecting source rock + stable shallow reservoir-cap rock combination”. The hydrocarbon accumulation in shallow slope-subsag area shows “inverted funnel” pattern controlled by “uplift in subsag + late fault” and “deep ridge for gas migration + late fault”. At present, the exploration target in shallow formations in Bohai Sea is dominated by lithologic oil and gas reservoir, and the exploration should be focused on “late fault for gas migration + lithologic trap” combination controlled by the Neotectonic movements.

The Permian Fengcheng Formation is the main source rock and exploration target in Mahu Sag, and the identification of shale oil and gas potential in deep formations has important guiding significance for further exploration activities. Based on shale gas discoveries in Fengcheng Formation in Well Fengyun 1 and exploration achievements in the underlying pre-Fengcheng Formation, the lithologic characteristics, hydrocarbon generation conditions of source rock, and reservoir conditions in Well Fengyun 1 have systematically been analyzed, and the distribution sequence of shale oil and gas in Fengcheng Formation in Mahu Sag has been determined, showing great geological significance. The study results show that Fengcheng Formation in Well Fengyun 1 is mainly composed of salt rock, shale, and silty-fine sandstone; Fengcheng Formation source rock has a relatively low organic matter abundance, and that in the first member has the best quality, with an average TOC of 1.06%; The reservoir is generally tight with an average porosity of 4.65%, and the dolomitic shale and limy sandstone have relatively better physical properties. With the increasing depth, a complete hydrocarbon distribution pattern from shale oil, to shale oil and gas, and to shale gas occurs in Fengcheng Formation in Mahu Sag. In addition, pre-Fengcheng Formation shows good resource potential with hydrocarbon source supplied by the ultra-deep oil and gas system, which is a major field for further exploration.

In recent years, a major discovery of oil and gas exploration in ultra-deep clastic rocks has been achieved in Linhe Depression of Hetao Basin by increasing the geological understanding of late oil and gas accumulation in deep ultra-deep clastic rocks.Based on the thermal simulation of Paleogene source rocks, drilling and logging data and analysis of reservoir formation and accumulation evolution, three important geological understandings are mainly formed.（1）High-quality source rocks rich in resinite ( terrestrial ) and algae ( aquatic ) are developed in the Paleogene in the northern part of Linhe Depression. The source rocks begin to generate and expel a large amount of hydrocarbons in the low evolution stage, which has the characteristics of high hydrocarbon generation intensity and wide hydrocarbon generation window. The ultra-deep thermal evolution degree of the trough area is relatively high, and the potential of oil and gas resources is large.（2）The braided river delta deposits are developed in the shallow slope of the far source water, and the sand bodies are widely distributed. Affected by weak diagenesis such as low geothermal temperature, late deep burial, high quartz content, weak compaction and weak cementation, a new mechanism of reservoir formation and storage is put forward, which is dominated by weak diagenesis and pore preservation, and superimposed by epigenetic ultra-high pressure transformation and fracture expansion. The reservoir has good physical properties and greatly expands the space of ultra-deep oil and gas exploration. （3）A new understanding of conventional oil and gas accumulation is put forward, which includes early filling in hydrocarbon generation period, continuous subsidence, deep buried thermal evolution, accelerated hydrocarbon generation and expulsion, continuous filling to form supersaturated and ultra-high pressure oil and gas reservoirs, and natural fracturing of reservoir-source interaction bodies by ultra-high pressure, forming fracture-pore connectivity, source-reservoir convergence and continuous large-area distribution, which effectively improves the exploration potential of ultra-deep conventional oil and gas reservoirs.The above studies show that the ultra-deep oil and gas accumulation conditions of the Paleogene Linhe Formation in the northern part of the Linhe Depression are superior. Combined with the large area of favorable exploration areas, it shows a good exploration prospect. At the same time, it further enriches the theoretical understanding of the late oil and gas accumulation of ultra-deep clastic rocks. It has important guiding significance for the exploration of similar basins, especially the ultra-deep source of 10,000 meters.

The glutenite in Shahezi Formation in Xujiaweizi Fault Depression in Songliao Basin has a large burial depth and tight lithology. At present, due to the insufficient understanding of controlling factors for hydrocarbon accumulation, and limited by investment cost and exploration and development technology, no breakthrough has been achieved in reserves and production in Shahezi Formation. By using seismic, core, wireline logging, mud logging and experimental data, the controlling factors for tight gas accumulation in Shahezi formation are analyzed from aspects of hydrocarbon generation potential of coal measure source rocks, distribution of tight glutenites, reservoir physical properties and formation overpressure, so as to identify gas sweet spots and guide well location deployment. The study results show that the reservoir and source rock in Shahezi formation are superimposed, and the non-buoyancy dynamic process during the accumulation of tight gas leads to the occurrence of abnormal high pressure and the pattern of gas-bearing in the entire basin. The tight glutenite reservoirs in Shahezi Formation are superimposed vertically and laterally, and multi-layer high porosity zones in the reservoir serve as the “sweet spot” of tight glutenite gas reservoir. Guided by the tight gas accumulation theory, the distribution of high-quality gas “sweet spot” has been accurately characterized and the optimal well trajectory has been designed. By giving full play to the advantage of geology and engineering integration, and aiming at the optimal and fast drilling operation and maximum reservoir reconstruction volume, a well Songshen 9-Ping 5 has been deployed, and the gas rate of 106×10⁴ m³/d has been tested, marking a major breakthrough in tight gas reservoir in Shahezi Formation, which brings broad prospects for the future exploration and development of tight gas reservoir in Shahezi Formation in Songliao Basin.

Small progress has been made in the exploration and development of shale gas in the Lower Cambrian Qiongzhusi Formation over the years. The high-yield gas flow in Well Zi 201 has greatly increased confidence in the large-scale and commercial development of shale gas in Qiongzhusi Formation. The different enrichment laws in various areas and layers and the optimal selection of favorable areas are the primary problems to be solved for shale gas development. Based on the analysis of paleontology, sedimentary facies, and reservoirs in 57 wells in Sichuan Basin, the theoretical basis for the deployment of Well Zi 201 and enrichment conditions of shale gas in Qiongzhusi Formation are analyzed in detail, and the exploration and development orientation are pointed out. Firstly, a stratification standard for Qiongzhusi Formation is established. It is clarified that four sets of organic rich shale of deep shelf facies were developed in Qiongzhusi Formation (layers ①, ②, ③, and ④), which were controlled by the development of rift troughs, with the largest shale thickness in the trough. The characteristics of shale reservoirs are analyzed, which indicate that the reservoir pressure, porosity, and gas saturation show an increasing trend from bottom to top, and from the outside to the inside of the rift trough, and reservoir overpressure plays an important role in the preservation of shale pores. On this basis, an overpressure and differential shale gas enrichment mode of “different facies in multiple layers and overpressure pore preservation” in Qiongzhusi Formation has been established, and it is pointed out that the overpressure pore development area (interval) far away from the dispersion pathway is the favorable area (interval) for shale gas enrichment. Finally, the study results indicate that Well Zi 201 and its surrounding areas are the main areas for increasing shale gas reserves and production in the future, with resources of 8.06×10¹²m³. It shows considerable development potential in western Sichuan Basin, with resources of 0.72×10¹²m³. Affected by graphitization and tectonic activities, areas with overpressure pore development far from weathered crust and surface outcrops are favorable for shale gas exploration in Changning in southern Sichuan Basin and northern Guizhou Province.

Seismic exploration is a system engineering based on seismic acquisition technology. The transformation of seismic acquisition technology is not only the starting point of equipment upgrading and theoretical innovation, but also the source for solving technical problems in seismic processing and interpretation. The development history of seismic exploration reflects the driving role of equipment capacity improvement, geological study demand, and progress of wave field theory. Among them, seismic acquisition technology is full of vitality and faces great challenges. Given the rapid development of big data and artificial intelligence, the reflection wave seismic acquisition technology, characterized by CMP stack and using sparse, regular, and single observation system, is increasingly unadaptable for imaging of small-scale, non-layered and non-uniform media. Meanwhile, the application of scattered wave seismic acquisition technology characterized by CMP discretization and using stochastic, ergological, and multi-observation system is imperative, so as to meet the imaging requirements of small-scale, non-layered, and subtle targets. Similarly, as the theoretical basis of scattered wave seismic acquisition technology, the study on stochastic theory and probability wave theory is gradually emphasized.

Shale oil is an important strategic resource to ensure China’s long-term steady and increase of oil production. The evaluation of oil-bearing property and oil mobility has an important guiding significance in sweet spot prediction in shale oil exploration. By applying the liquid nitrogen freezing sampling and rock pyrolysis experiment methods, experimental research on oil-bearing property and mobility evaluation of shale oil series in the Jurassic Lianggaoshan Formation in northeastern Sichuan Basin is conducted, and the influencing factors of oil-bearing property are analyzed. As a result, understanding is obtained in the following four aspects: (1) The liquid nitrogen freezing sampling technology effectively avoids the loss of light hydrocarbons in samples, and the obtained oil-bearing property parameters can better reflect the oil-bearing property of the reservoir; (2) By using the multi-stage rock pyrolysis method, the oil-bearing property is characterized by free oil, bound oil, and solid hydrocarbon content, and the oil mobility is characterized by the proportion of maximum mobile oil content (free oil/total oil content); (3) The oil-bearing property and mobility of shale oil reservoir in Lianggaoshan Formation are jointly affected by organic matter abundance, maturity, lithology, as well as hydrocarbon expulsion, migration, and accumulation in the source rock system. The greater the organic matter abundance, the higher the oil-bearing property of the reservoir, and the higher the maturity, the better the oil mobility. However, a better oil-bearing property and oil mobility will more easily cause the short-distance oil migration and accumulation in the reservoir, thus changing the oil-bearing property of the reservoir; (4) After the comprehensive analysis of oil-bearing property, oil mobility, geochemical characteristics, physical properties of the first and the third members of Lianggaoshan Formation, as well as the development demands of shale oil wells, it is found that the first member of Lianggaoshan Formation is a high-quality interval for shale oil exploration. The rock pyrolysis experiment provides a new idea and method for the evaluation of shale oil-bearing property and oil mobility, which effectively supports the prediction of shale oil sweet spot area and the design of development plan.

The fracturing construction curve contains information of artificial fractures and reservoir, which is the basis for evaluating fracturing results. At present, the evaluation of fracturing results mainly relies on the theoretical and statistical methods, which have limited guidance for the improvement and optimization of fracturing technology. In order to fully tap the hidden information in the construction curve, a sample library is constructed for the image of fracturing construction curve based on the classification of open flow rate after fracturing. The convolution neural network CNN in artificial intelligence is used for training, and an evaluation model is established based on the capacity classification, Then, the interpretability study is conducted by using Grad-CAM to find out the main reference position for artificial intelligence identification, so as to guide the optimization and improvement of the fracturing technology. The research results show that the accuracy of fracturing curve classification by CNN is higher than 85%. The key to the fracturing results lies in the early and late stages of fracturing construction, mainly including the initial fracturing displacement and corresponding pressure rise rate, pump stop pressure, and slug duration, and production capacity can be improved by changing fracturing construction parameters. This method enables to optimize and improve fracturing construction with targeted measures.