During the 14^th Five–Year Plan period, PetroChina Company Limited (hereinafter referred to as “PetroChina”) has been committed
to high-quality development of oil and gas exploration, and vigorously advanced efficient exploration guided by the Seven–Year Action Plan. As a result, 30 significant results in five major fields have been achieved in domestic oil and gas exploration, including marine carbonate rocks, continental lake basin lithologic–stratigraphic traps, foreland thrust belts, shale oil and gas, and deep coal rock gas, forming nine largescale oil reserve areas and seven large-scale natural gas reserve areas by intensive exploration activities. The exploration achievements show distinct characteristics of multiple breakthroughs in various fields on the plane, simultaneous exploration of both shallow and deep formations in vertical direction, and parallel advancement of both conventional and unconventional resources. Specially, breakthroughs have been made in long-stalled fields such as the southern margin of Junggar Basin and the piedmont zone of southwestern Tarim Basin. In addition, breakthrough progress has been made in oil and gas geological theories in aspects such as marine carbonate rocks, lithologic–stratigraphic traps in continental lake basin, and coal measure whole petroleum system. Furthermore, key engineering technologies have been developed, represented by 3D seismic imaging in “double high” and “double complex” areas, efficient well drilling and completion in deep to ultra-deep formations, and geology and engineering integrated fracturing for deep coal rock gas. In response to the new situation of oil and gas exploration at home and abroad during the 15^th Five–Year Plan period and resource endowment in China, PetroChina will adhere to efficient exploration, strengthen risk exploration in key zones in the five major fields, actively prepare for strategic replacement areas and major replacement fields, focus on centralized exploration in “10 oil and 10 gas” exploration fields, and promote continuous large-scale reserve growth of conventional oil and gas and rapid development of unconventional resources, so as to consolidate the resource foundation for high-quality development.

Since the 14^th Five–Year Plan period, by focusing on three major tasks of expanding resource scale, increasing proven reserves, and
expanding mining rights areas, Sinopec has strengthened research on basic scientific issues, and continuously tackled engineering supporting technologies, achieving multiple major breakthroughs, with the new addition proven oil and gas reserves doubled compared to the 13^th Five–Year Plan period: (1) It has innovated exploration theory and technological system for lake basin shale oil, and made significant breakthroughs in various types of shale oil in Jiyang, Fuxing, and Subei areas. (2) It has deepened the “dual enrichment” theory of shale gas, and made significant breakthroughs in the Permian in the eastern and northern Sichuan Basin and Cambrian new formations in the southern Sichuan Basin. (3) It has developed the theory of strike slip faults controlling hydrocarbon accumulation in marine carbonate rocks, rapidly forming a one-billion-ton level condensate oil and gas reserve area in the central Shunbei area. (4) It has conducted research on “fault–facies” dual controlling hydrocarbon enrichment model in clastic rocks, achieving large-scale reserve increase in Sichuan Basin, Junggar Basin, and Ordos Basin. (5) It has innovated new understanding of reservoir formation and hydrocarbon accumulation in mature areas, achieving oil and gas breakthroughs in sub-source rocks in deep subsag, lacustrine carbonate rocks, and lithologic trap in subsags. (6) It has strengthened the protype basin modeling and strategic exploration zone evaluation, and significant breakthroughs have been made in areas with low level of exploration, such as Songliao Basin new areas, Yingen–Ejina Basin, western piedmont belts, and sea areas. (7) It has researched on enrichment theory and key technologies for deep coalbed methane, and made significant breakthroughs in Daniudi and Fuxian areas in Ordos Basin. Looking forward, Sinopec upstream sector should seize opportunities, strengthen confidence in resources, and scientifically respond to challenges, and increase exploration efforts in the multiple aspects, including expanding and holding mining rights, increase economically beneficial shale oil and gas reserves, strategic breakthrough in deep oil and gas in the central and western regions, deep natural gas in the eastern region, and exploration in middle–deep water sea areas, so as to achieve major breakthroughs and new oil and gas discoveries and contribute to safeguarding national energy security.

During the 14^th Five–Year Plan period, Shaanxi Yanchang Petroleum (Group) Co., Ltd. (referred to as Yanchang Petroleum)
has continued to increase its exploration and development efforts, and has made significant progress in the exploration, development, and theoretical technology of low-permeability–tight oil, shale oil, and natural gas in Ordos Basin. (1) In the field of low-permeability–tight oil, the theory of “alternating” oil accumulation has continuously been deepened, proposing a “spatially and temporally orderly near source oil accumulation” model for tight oil, and a “rate controlling and permeability increasing water injection” technology and open hole well area secondary development technology have been formed for low-permeability–tight oil, with new addition proven oil geological reserves of nearly 3.5×10⁸t, laying solid foundation for steady crude oil production with an annual output of over 10 million tons. (2) In the field of shale oil, the exploration orientation of “production capacity construction in ClassⅠzone, research and development in Class Ⅱ zone, and strategic reserve in Class Ⅲ zone” has been established, and an integrated technical system of shale oil geology–engineering–development has been constructed, with new addition proven shale oil geological reserves of nearly 0.5×10⁸t, and an annual output of 35×10⁴t. (3) In the field of natural gas, the theoretical understanding of “sand controlled by frequent migration of shallow water shorelines” in the Upper Paleozoic has been deepened, and a gas accumulation model with superimposed weathered crust gas reservoirs and carbonate rock inner gas reservoirs in the Lower Paleozoic has been proposed, achieving initial exploration results in new types, new formations, and new fields, with new addition proven gas geological reserves of approximately 2800×10⁸m³, and an annual output exceeding 10 billion cubic meters. Based on a systematic review of oil and gas exploration and development achievements and theoretical and technological advancements during the 14^th Five–Year Plan period, Yanchang Petroleum has outlined its exploration and development orientations during the 15^th Five–Year Plan period. First, the company will continue to uphold the resource strategy of “stabilizing oil production, increasing gas output, and strengthening unconventional resource production”, and make efforts on key exploration technological research of ultra-low permeability–tight oil, tight sandstone gas, and carbonate gas to solidify the resource foundation for long-term development. Second, the company will vigorously expand unconventional resources such as shale oil, coalbed methane, and shale gas, and cultivate strategic replacement fields, striving to drive continuous innovation and high-quality development in oil and gas exploration and development.

Implementing the differentiated and fine management of oil and gas exploration and development within the ecological protection
red line areas, and coordinating the relationship between oil and gas resource development and environmental protection are conducive to promoting the “development while protecting, and protection in development” of oil and gas industry, enhancing the increase of oil and gas reserves and production, and assisting the strategic activities for obtaining breakthrough in a new round of mineral exploration. After systematically reviewing the control rules for oil and gas exploration and development within the domestic ecological protection red line areas and referring to the foreign management practice for oil and gas exploration and development within nature reserves, the problems in the current policies for controlling oil and gas mining rights within the ecological protection red line areas have been analyzed, which shows that the differentiated and fine management ideas should be implemented base on the characteristics of oil and gas resource exploration and development, and more scientific and rational control policies and access requirements for exploration and exploitation activities should be formulated for different protected objects. The control and assessment of oil and gas resource exploration and development activities within the ecological protection red line areas should be strengthened, and various requirements for ecological protection should be strictly implemented with high standards.

During the 14^th Five–Year Plan period, in the face of the complex situation where exploration targets gradually shifted towards “low grade, unconventional, difficult-to-utilize, and deeply buried” resources, as well as multiple challenges in fundamental theoretical understanding and supporting technologies, PetroChina Daqing Oilfield Company (Daqing Oilfield) has adhered to the overall layout of “focusing on Northeastern China, accelerating development in Western China, balancing conventional and unconventional resources, advancing both oil and gas, and exploring both shallow and deep targets”. By deepening fundamental research, advancing cutting-edge theoretical innovation, and accelerating technological iteration and upgrading, multiple strategic breakthroughs and large-scale reserve increase across various fields have been achieved, strongly supporting the robust rise of the oilfield’s “second curve”. Through continuous research efforts, the Company has made groundbreaking progress in several key fields: (1) It has developed a whole oil and gas system theory, innovatively developed a dual sweet spot evaluation technique, and first proposed the in-situ accumulation theory of Gulong shale oil, driving the large-scale reserve increase and profitable production of conventional oil, tight oil, and shale oil in the northern Songliao Basin; (2) It has deepened the understanding of hydrocarbon enrichment law in multi stage superimposed basin, and innovatively established models of uplift zone controlling reservoir
development and hydrocarbon accumulation, proving a 300-billion-cubic-meter giant gas field in Maokou Formation in Sichuan–Chongqing exploration area; (3) It has reshaped the migration and evolution laws of foreland lake basin, making a historic breakthrough in shale oil production in Sichuan–Chongqing exploration area; (4) It has refined the theory of hydrocarbon accumulation in complex faulted basin, and established unconventional hydrocarbon accumulation mode, achieving significant breakthroughs in the exploration of intra-source tight oil in Hailar Basin; (5) It has constructed the hydrocarbon accumulation model in platform marginal reef beach fault–karst complex, and broken through extreme geological conditions such as “ultra-depth, ultra-high pressure, and ultra-high temperature”, preliminarily forming a 100-billion-cubic-meter reserve zone in Yuman platform marginal zone in Tadong exploration area. Looking ahead, in response to severe challenges such as significantly reduced mining rights areas, increasingly complex exploration targets, and heightened difficulties in profitable exploration, the Company will seize the opportunities of strategic transformation, and forge a new path towards the high-quality development characterized by resource replacement, technological leadership, and green intelligence. It will scientifically plan its exploration orientations
and key tasks, and comprehensively promote five major projects, including large-scale reserve increase in Songliao Basin, stereoscopic reserve increase in Sichuan–Chongqing exploration area, rapid reserve increase in Tadong exploration area, reserve replacement and increase in Hailar Basin, and reserve succession and increase in new exploration areas and fields, taking on the responsibility of building a world-class modern century-old oilfield, and continuously contributing Daqing’s strength to ensuring national energy security.

The conventional oil and gas exploration and development have dominated in Ordos Basin for a long time. With the increasing
exploration level, it has gradually shifted to intra-source exploration. However, in response to the long-term demands for steady oil and gas production, exploration faces significant challenges. The major exploration progress, achievements, and key geological understanding of hydrocarbon accumulation in Ordos Basin since the 14^th Five–Year Plan period have systematically been reviewed: (1) Effective source rocks were developed in the Mesozoic, Upper Paleozoic, and deep formations in Ordos Basin. Among them, the Mesozoic and Upper Paleozoic source rocks have highly been proved, which served as the main source rocks for exploration. In addition, two sets of low-abundance source rocks were developed in the Ordovician, and both had large-scale hydrocarbon generation potential, in which Wulalik Formation source rock had a large thickness and continuous distribution, while the Ordovician inter-salt layer had a thin individual layer thickness but huge cumulative thickness. (2) Besides the strong hydrocarbon generation capacity, the innovative understanding has been formed that the three major stratigraphic sequences had favorable reservoir physical properties, marking a concept transformation from a simple source rock to a source rock–reservoir integrated system, and the intra-source or near-source accumulation was more conducive to gas enrichment. (3) Based on the exploration level and source rock proven degree, future exploration will be conducted in two tiers. The first tier focuses on the realistic exploration fields, including the Mesozoic shale oil, Upper Paleozoic coal rock gas, and western marginal Qingshimao tight gas; The second tier includes the replacement exploration fields such as the lower combination in the Mesozoic Yanchang Formation, Upper Paleozoic transitional facies shale gas, Ordovician inter-salt layer, Ordovician in the western basin, and Cambrian–Mesoproterozoic–Neoproterozoic. In the exploration practice, it is essential to deepen fundamental geological study and innovate hydrocarbon accumulation theory in new fields, while strengthening 3D seismic deployment, enhancing exploration supporting technologies, and optimizing reservoir stimulation techniques, so as to promote the large-scale reserve increase in realistic exploration fields and achieve breakthroughs in new formations and fields, providing resource guarantees for long-term steady oil and gas production in Ordos Basin.

After nearly 30 years of large-scale oil and gas exploration of Tarim Oilfield, there are still abundant remaining oil and gas resources in Tarim Basin, but the current exploration replacement fields are unclear. During the 14th Five-Year Plan period, a series of significant exploration achievements have been achieved in the following aspects. In Kuqa Depression in the northern basin, based on a new round of structural modeling and full strata interpretation, the fault combination characteristics in the stable–transition zone of Kelasu Structural Belt have been re-studied, discovering a total of 26 new gas reservoirs in Bozi–Dabei area, and basically constructing a 1-trillion-cubic-meter level large gas area. In Aman transition zone, a hydrocarbon accumulation model of “multi-stage hydrocarbon supply by the Cambrian source rocks, reservoir controlled by fault fractured zones, in-situ vertical migration and accumulation along strike-slip faults, and segmented enrichment in fault zones” has been established, forming the geological understanding of strike-slip faults controlling reservoir formation, hydrocarbon accumulation and enrichment, and identifying Fuman 1-billion-ton level large oilfield. For new exploration areas and fields, centering on the hydrocarbon-generating sags, characterization of the petroleum system, near-source regional reservoir–cap rock combinations, and largescale source-connecting faults has been focused, achieving successive breakthroughs in risk exploration in four new areas and fields, i.e., the
Carboniferous–Permian in the piedmont zone of the southwestern Tarim Basin, Cretaceous–Triassic in the piedmont Kuqa Depression, Upper Cambrian in the west part of the northern Tarim Basin, and the Ordovician in Maigaiti Slope of the platform-basin area. In the exploration practice, based on the high-quality basin-wide stratigraphic framework study, and guided by the risk exploration of near-source targets, a high-efficiency exploration path for ultra-deep formations has been formed by adhering to the advanced deployment of 3D seismic surveys and continuous research on key seismic technologies. Furthermore, the future exploration orientation has been clarified to find strategic replacement areas in hydrocarbon-generating center and approaching source rocks, including five major fields of the piedmont zone in the southwestern Tarim Basin, middle combination in Kuqa Depression, west part of the northern Tarim Basin, periphery of Awati Sag, and the sub-salt Cambrian.

Beibuwan Basin serves as a crucial oil and gas production base in the northern South China Sea. During the 14^th Five–Year Plan
period, oil and gas exploration practice faced key challenges such as the enrichment mechanism and development technology for offshore shale oil, hydrocarbon accumulation patterns of deep subsags and buried hills, differential oil enrichment in deep low-permeability reservoirs, and accurate identification of subtle traps. The theoretical advances and technological progress during this period have systematically been reviewed, obtaining the following key achievements: (1) An innovative “source rock–reservoir–migration” ternary coupling hydrocarbon accumulation model for offshore shale oil has been developed, along with large-volume fracturing technology in confined workspace, leading to China’s first breakthrough in offshore shale oil exploration and the subsequent discovery of Weizhou 11-6 Oilfield—the largest oilfield in the western South China Sea; (2) The “lithofacies–paleogeomorphology–structure” ternary reservoir controlling mechanism for carbonate buried hills and a hydrocarbon accumula tion model of “high-maturity source rock connection and overpre ssure hydrocarbon charging” for granite buried hills have been established, guiding a series of major discoveries in buried hills and deep natural gas exploration in Weixinan Sag; (3) The mechanism of “source-ridge controlling oil migration, pervasive–sequential oil charging, and differential oil accumulation” has been elucidated, promoting breakthroughs in the exploration of deep low-permeability oil reservoirs in Weixinan Low Bulge, with new addition proven reserves of over 2500×10⁴t oil equivalent. The research achievements mark a systematic shift of exploration in Beibuwan Basin from conventional to unconventional resources, from shallow to deep formations, and from structural to structural–lithologic traps, significantly expanding the resource potential. In the future, efforts should focus on four key fields, including source rock–reservoir connected buried hills, structural–lithologic traps in middle–deep formations, laminated/interlayered type shale oil, and potential hydrocarbonrich sags, and the coordinated theoretical and technological research should be strengthened, so as to provide solid support for achieving largescale reserve growth in the basin and ensuring national energy security.

Pearl River Mouth Basin is a large proliferous basin on the northern continental margin of the South China Sea, in which multiple
large- and medium-sized oilfield groups such as Huizhou, Xijiang, and Lufeng have been discovered. During the 14^th Five-Year Plan period, further exploration achievements have been obtained in the shallow–middle formation in Eastern Pearl River Mouth Basin, while the exploration has actively been marched toward the “four new” (new formations, new structural zones, new subsags, and new types) frontier fields. As a result, major theoretical advancements and technological innovations have been made in deep-formation in rich hydrocarbon generation depression, and shallow-middle formation in rich hydrocarbon generation depression, and deep-water exploration fields, resulting in significant exploration results. In deep-formation exploration field, addressing challenges of “fragmented traps, rapid reservoir facies changes, and poor preservation conditions” of deep formation of ZhuⅠDepression, traditional understanding constraints have been broken through, and the new “deep oil and gas exploration theory and technology for composite marginal basin” have innovatively been developed, discovering multiple large- and medium-sized oilfields such as Huizhou 19-6 and Lufeng South in deep formations in Huizhou and Lufeng sags, among which Huizhou 19-6 Oilfield is the largest clastic rock oilfield with a level of 100 million tons in the South China Sea. In shallow–middle formation exploration field, deep research has been conducted on hydrocarbon migration problems, and the target level fine “source rock–fault–facies–trap” four-element coupled hydrocarbon controlling quantitative evaluation system has been established, guiding a series of follow-up discoveries around Xijiang, Huizhou, and Panyu oilfield groups. In deep-water exploration field, the innovative “continental margin core complex rocks–decoupling sag hydrocarbon accumulation theory” has guided the discovery of Kaiping South Oilfield with a level of 100 million tons, which is the first deep-water and deep-formation 100-million-ton level light oilfield in China, fully demonstrating the broad prospects of deep-water and deepformation fields. In deep-water natural gas exploration field, research has been conducted on deep-water reservoir formation mechanism and lithological trap formation mechanism, obtaining commercial or potentially commercial discoveries such as Liuhua 28-2 and Liwan 4-1 gas fields, with Liwan 4-1 representing China’s first major breakthrough in the ultra-deep water carbonate rocks. During the 15th Five–Year Plan period, the strategic exploration orientations and priorities will continue to be scientifically planned in Eastern Pearl River Mouth Basin, focusing on four key exploration fields, including the deep to ultra-depth Paleogene in rich hydrocarbon generation depression, lithological reservoirs in the shallow–middle Neogene in rich hydrocarbon generation depression, new sags, and deep-water natural gas, accelerating the identification of large-scale oil and gas plays for increasing reserves, and actively exploring in prospective fields such as buried hills, glutenites, and Mesozoic residual basins, so as to strengthen the resource foundation for high-quality development.

It shows complex gas accumulation conditions in Hangjinqi area in the northern marginal transition zone of Ordos Basin. The
exploration understanding has undergone a major evolution from “gas accumulation controlled by local structures” to “gas accumulation controlled by large-scale lithologic traps”, and from “single low-saturation lithologic gas reservoirs” to “orderly distribution and differential enrichment of multi-type gas reservoirs”. In particular, since the 14^th Five–Year Plan period, significant discoveries have successively been made in Xinzhao play, Shiligahan play, and newly recognized formation in the Mesoproterozoic, building a trillion-cubic-meter-level gas province. Based on new exploration achievements, and combined with new well drilling, seismic, and geochemical experimental data, the differentiated gas accumulation and enrichment processes have been analyzed in detail, obtaining the following new insights: (1) Two sets of high-quality source rocks in the Carboniferous–Permian Taiyuan and Shanxi formations are distributed in the circum-paleo-uplift, which laid the fundamental resource basis for the formation of large gas fields in the basin marginal transition zone; (2) The widespread nearsource gravelly braided-river channel-bar sand bodies in Taiyuan–Shihezi formations controlled the orderly distribution of tight–conventional reservoirs in the basin marginal zone after superimposed by differential tectonic evolution; (3) The predominant migration and transport framework composed of faults and sand bodies during key accumulation periods governed gas adjustment and enrichment; (4) On the basis of understanding of gas accumulation conditions, four dynamic gas accumulation models have been established by integrating static and dynamic accumulation elements in major gas provinces, namely near-source–middle-stage accumulation, distal-source–multi-stage accumulation, intra-source–late-stage accumulation, and upper source rock–lower reservoir type buried hill accumulation. The study results further expand and enrich hydrocarbon accumulation and enrichment theories of the whole petroleum system in large cratonic basins, and provide important guidance for oil and gas exploration in the super large Ordos Basin.

The weathered crust reservoir was encountered at the top of the Lower Paleozoic Ordovician in a risk exploration well Huangu 1 on the west side of Central Paleo Uplift, Ordos Basin, showing good gas shows, which confirmed that the west side of Paleo Uplift is a major replacement field with promising gas exploration potential. Focusing on the west side of Central Paleo Uplift, and using regional logging, lab testing, 2D and 3D seismic data, a comprehensive analysis of gas accumulation conditions in the Ordovician has been conducted, which indicates that the west side of Central Paleo Uplift was controlled by Fault No.I, with the Ordovician strata relatively well preserved, developing main target layers corresponding to the third and fourth members of Majiagou Formation (Ma 3 and Ma 4 members) in the eastern basin. The weathered crust was primarily developed at the top of the Lower Paleozoic Majiagou Formation, where karst fractured–cavity type reservoirs were easily formed after weathering and leaching, while the bauxite reservoirs were formed in the overlying Taiyuan Formation above weathered crust influenced by karst paleogeomorphology. Two sets of source rocks were deposited near the weathered crust, including the Upper Paleozoic coal seams and the Lower Paleozoic Majiagou Formation dolomitic mudstone, among which the former exhibited favorable hydrocarbon generation conditions. The faults were well developed to the west of Fault No.I, forming an “alternating horst–graben” structural pattern. These faults served as favorable pathway connecting the Upper Paleozoic coal measures and the Lower Paleozoic marine source rocks, resulting in dual hydrocarbon supply conditions on the west side of Paleo Uplift. Three favorable gas accumulation models have been established in the west side of Central Paleo Uplift, i.e., fault-horst residual platform type, fault-horst residual accumulation type, and isolated residual mound type. Furthermore, in the context of dual hydrocarbon supply, it is pointed out that the further exploration orientations include the structural horsts matching the weathered crust reservoirs, as well as the updip interval and mound uplifts in the grabens.

In response to the great difficulty in evaluating oil and gas-bearing zones of the Ordovician carbonate rocks in the central–southern Tarim Basin caused by overall low exploration levels and complex hydrocarbon accumulation conditions, a petroleum system centered on the Lower Cambrian source rock has been constructed using the hydrocarbon accumulation dynamics method. The mixed-flow algorithm has been applied to conduct the dynamic simulation of hydrocarbon accumulation in the Ordovician, and the differential evolution history of “generation–migration–accumulation” in 12 oil and gas-bearing zones has been restored. The study results show that source rocks in the Lower Cambrian Yurtus Formation underwent an early oil generation in the mature stage and a late dry gas generation in the highly–over mature stage, and three stages of oil and gas charging occurred in the Late Caledonian, Hercynian, and Himalayan periods. The deep oil and gas in the central–southern Tarim Basin always maintained a dynamic balance between migration/accumulation and dissipation, which can be divided into five charging–dissipation modes. Three hydrocarbon enrichment patterns have been established, including “hydrocarbon supplied by deep sag, transport controlled by faults, accumulation in uplift zone, and east-gas and west-oil”, “hydrocarbon transport controlled by faults, accumulation by horizons, gas enrichment in anticline core, and rich oil in flanks”, and “lower source rock and upper reservoir, accumulation controlled by faults, and deep gas and shallow oil”. The comprehensive assessment has delineated three favorable exploration zones of the Ordovician in the central–southern basin, namely Yubei fault zone in Yuzhong low bulge–Mazatag fault zone and its periphery, northern Qibei–Guman structural belt in Yecheng Sag, and the intersection zone between NW-trending thrust fault zone and NE-trending strike-slip fault zone in the western Katak Uplift, with areas of 8500 km², 5000 km², and 2900 km², respectively, the estimated total oil resources of 2366×10⁴t, and gas resources of 1.4331×10⁸t.

Faced with well drilling and completion technical challenges in the fields of deep formations, deepwater, unconventional resources,
and mature oilfields, China has developed a series of major equipment, tools, instruments, and working fluids with independent intellectual property rights during the 14^th Five–Year Plan period. The integrated technical system has been established, including drilling and completion technologies for 10000-meter ultra-deep wells represented by “15000-meter automated drilling rig, high-temperature resistant downhole motor tools and efficient PDC bits, and 240 °C high-temperature resistant wellbore working fluids”. The unconventional oil and gas horizontal well drilling technologies have been iteratively upgraded, which are represented by “domestic rotary geosteering system and one-trip drilling for long horizontal section”. The drilling technologies for sidetracking and multilateral wells represented by “small-radius horizontal well” in mature oil and gas fields have been innovated and promoted. Breakthroughs have been made in key technologies and equipment for offshore deepwater well drilling, such as “offshore drilling automatic feedback dynamic well control system and deepwater riser system”. The well drilling technologies for new energy and low-carbon business, represented by “U-shaped horizontal wells”, have been developed. The digitalization and intelligentization of well drilling operations have continuously improved, strongly supporting the increase in oil and gas reserves and production and enabling high-quality development. Looking ahead to the 15^th Five–Year Plan period, the domestic upstream sector faces increasing difficulties in achieving cost-effective development of remaining recoverable reserves and the large-scale utilization of newly proven reserves. It poses a series of new challenges for drilling technologies in promoting the increase in oil and gas reserves and production and the integrated development of new energy businesses. By adhering to the directions of intelligentization, greening, and integration, it is essential to accelerate research and development of intelligent well drilling technologies, iteratively upgrade drilling technologies for 10000-meter ultra-deep well and unconventional oil and gas horizontal well, research 5-level multilateral well drilling technologies, and accelerate breakthroughs in safe and efficient drilling technologies for 1500-meter deepwater wells and high-temperature geothermal wells.

During the 14^th Five–Year Plan period, China National Petroleum Corporation (CNPC) has kept pace with international logging technology trends and domestic and international oil and gas exploration and development needs. Through overall planning and continuous iteration, CNPC has upgraded its portfolio of autonomous equipment for well logging and perforation, innovated the “dual-high” petrophysical technology series, developed the “dual-multi” and “dual-integration” logging evaluation technology series, and promoted the transformation and upgrading of well logging processing and interpretation towards informatization and intelligentization, resulting in key technological advancements in nine aspects. During the 15^th Five–Year Plan period, CNPC will align with global energy transition and intelligent development trends, continue to focus on the needs of “two deeps, one unconventional, and one mature” oil and gas fields and the exploration and development of wellbore-associated resources, target at world-class development goals, and persistently improve foundational infrastructure and platform development. It will advance research on core methods and equipment such as asymmetric multi-physics logging, extreme-environment logging tools, integrated “logging & geosteering” in one trip drilling, and downhole Internet of Things (IoT) for oil and gas reservoirs. In addition, it will promote the development of key technologies and products including near-wellbore geological body imaging, transparent oil reservoir logging, and artificial intelligence application, so as to steadily achieve iterative upgrade and intelligentizatio transformation of logging technologies.

As one of the typical low-porosity and ultra-low permeability oilfields in Erlian Basin, the development situation of Wuliyasitai
Oilfield is increasingly severe after years of exploration and development activities, which is faced with the problems of weak resource replacement ability, difficult identification of high-quality reservoirs, and poor benefits of vertical well development. Therefore, focused on the stock reserves area, new strategies for profitable development of low-grade reserves have been researched and formed by referring to the concept of efficiency and benefit improvement in tight oil development: (1) Accurate selection of favorable zones and layers. Through the fine analysis of facies controlled oil reservoir units and development effects, the favorable reservoir distribution and oil reservoir development characteristics have been clarified, and the types of remaining resources with horizontal well development potential have optimally been selected to support the well location deployment. (2) Precise and ingenious well location design. The principle of horizontal well deployment for low-grade oil reservoirs has been established, and three horizontal well models with a deviation angle of less than 85° have innovatively been designed to ensure the sweet spot drilling rates and drilling benefits, including “drilling through top or bottom of thick oil layer”, “targeted drilling for thin oil layer”, and “selected drilling for sweet spot in the upper and lower oil layers” (vertically multi-layer penetrating well drilling). (3) Strengthening on-site tracking while drilling and accurate evaluation after drilling, and optimizing reservoir reconstruction and energy supplementation methods. By applying “energy storage before fracturing, multi stage and multi cluster fracturing, intralayer temporary plugging, interlayer diversion, and online viscosity change”, the oil reservoir reconstruction effects have been improved. Based on the above technical sequence, the development method of “horizontal well with inclination angle less than 85°+ high-strength volume fracturing” has been tested in T21 block in Wuliyasitai Oilfield, increasing the average single well EUR to 3 times and the initial average single well daily oil rate by 3–4 times with the drilling investment equivalent to 1.5 times of vertical well, marking the significantly enhanced development benefits. The new strategies for the profitable development of low-grade reserves have effectively promoted the rapid conversion of low-grade resources in Wuliyasitai Oilfield and other areas in Erlian Basin, with remarkable phased achievements, showing considerable potential for promotion and application.