In recent years, the China National Petroleum Corporation (hereinafter referred to as CNPC) has made 13 major breakthroughs and new strategic discoveries and formed 10 large hydrocarbon provinces with reserves of over 100 million tons by following the principle of efficient exploration relying on domestic and expanding overseas markets. . Based on important domestic and foreign exploration progress since the beginning of the ‘13th Five-Year Plan’ period, and in view of the current situation and requirements at home and abroad, comprehensive analysis of the oil and gas resources situation in the CNPC mining rights blocks, the development potential of remaining resources and the challenges faced by the upstream business has been carried out. This has also clarified the general train of thought and strategic targets of CNPC's upstream business for the future: CNPC will adhere to steady development guidelines and high-quality development goals, and will implement strategies to find more oil and gas resources, the domestic upstream segment will reinforce exploration and development by focusing on the seven major basins, paying equal attention to oil and gas resources, and putting conventional and unconventional resources on an equal footing, the strategic target is to achieve annual newly increased proven petroleum geological reserves of more than 1.1 billion tons of oil equivalent in the period from 2019 to 2025, and to achieve oil and gas production of 220 million tons of oil equivalent by 2025; In overseas markets, CNPC will focus on conventional oil and gas resources, optimize the development of five cooperation zones (Central Asia-Russia, the Middle East, Africa, the Americas, and Asia-Pacific) and expand the scale of ‘Belt and Road’ cooperation. Five measures have been proposed to ensure the realization of these strategic targets, which include reinforcement of domestic exploration and development, implementation of high-quality and efficient development overseas, promotion of scientific and technological innovation, deepening of reform and management innovation, and strengthening of the fostering of high quality talent teams specializing in petroleum exploration and development.

Since the strategic reorganization of Sinopec, the company’s upstream resources strategy has been steadily promoted, and a development pattern has been established: from east to west; from oil to oil and gas; from conventional to unconventional, and new energy resources. This has formed a development trend of stable development of oil, rapid development of natural gas, orderly promotion of new energy resources, continuous optimization of the overseas oil and gas business, continuous improvement of supporting engineering technologies, and rapid advance of informatization and intelligent construction. Since 2016, remarkable achievements have been made in oil and gas exploration and development. Production and reserves in marine carbonate formations in the Tarim Basin and Sichuan Basin have achieved large-scale increases. Through fine exploration and development, benefit increase of reserves and production has been achieved in the eastern mature exploration areas. Exploration and development of clastic rocks in the central and western basins have realized benefit productivity construction. New breakthroughs have been made in the exploration and development of deep and normal-pressure shale gas in the Sichuan Basin. New progress has been made in overseas oil and gas exploration. Looking forward to the future, Sinopec takes safeguarding national energy security as its own responsibility, vigorously improving domestic oil and gas exploration and development, continuously optimizing overseas oil and gas exploration and development structure, accelerating construction of natural gas production, supply, storage and marketing systems, and actively promoting business development of new energy resources. The company will vigorously carry out high-quality exploration and benefit development, achieve large-scale reserves and production increase, and ensure successful achievement of the objectives of its ‘seven-year action plan’.

In the past two years, China National Offshore Oil Corporation (CNOOC) has made great efforts in domestic offshore exploration, carried out "value exploration" with the goal of finding recoverable reserves, strengthened risk exploration, and actively explored new areas and new domains. The resulting achievements have been impressive. Through continuous research, a considerable number of updated geological understandings and technological breakthroughs have been achieved. Important exploration breakthroughs have been made in three domains: buried hill in the Bohai Bay Basin, the deep-water area in the Qiongdongnan Basin, and the Yangjiang sag in the Pearl River Mouth Basin. In the immediate future, CNOOC will continue to vigorously expand exploration efforts, extend research on exploration domains such as deep formations, deep water, high-temperature and high-pressure formations, further explore potential rich hydrocarbon generation sags, and expand exploration domains and directions.

Shale gas exploration and development in China has entered a golden age of rapid progress. The increasing proportion of natural gas in the energy consumption structure of the nation, and the success of commercial shale gas development in the southern Sichuan Basin, indicate that shale gas will be the most reliable succession energy source for the future in China. This paper reviews achievements in theoretical understanding and technologies related to shale gas development over the past 10 years, summarizes successful experiences in commercial shale gas development, and clarifies the prospects for, and status of, shale gas in future natural gas development in China. China's shale gas resources have enormous potential, and provide a practical base for future growth in natural gas production. The conditions for obtaining industrial shale gas resources are described as ‘2 highs’ (high gas content and high porosity), ‘2 larges’ (large thickness of intervals with high TOC and large distribution areas), ‘2 moderates’ (moderate thermal evolution and moderate burial depth), and ‘2 goods’ (good preservation conditions and good fracability). Marine shale gas in China is of the highest potential, and at present is the major objective for natural gas production growth. Exploitation of the Ordovician Wufeng Formation and Silurian Longmaxi Formation shale gas in the Sichuan Basin and its surroundings has relied on developments in six technology areas: comprehensive geological evaluation; development optimization; fast drilling of horizontal wells; volume fracturing of horizontal wells; factory-like operation, and efficient and clean production. The successful achievement of commercial development of shale gas in China can be summarized as stemming from four key factors: ① optimized horizontal section targets; ② supporting technologies for effective and fast drilling and volume fracturing stimulation; ③ geological and engineering integration, and ④ advanced organization and management. Three proposals for the future development of shale gas in China are: ① to develop key technologies and equipment for low-cost development of non-marine and deep marine shale gas; ② to enhance block-scale shale gas recovery and achieve efficient development of the entire Sichuan basin; ③ to pay attention to the influence of non-resource factors on shale gas production.

It is of great practical and strategic importance to march deeper into the earth to explore deep oil and gas resources and to build up a solid resource base for energy security in China. There is therefore also a pragmatic imperative to increase the intensity of oil and gas exploration and development in China. Based on an exhaustive summary of the global situation in deep oil and gas exploration and development, and the progress that has already been made by China, the development potential, key research fields and scientific and technological research directions of deep oil and gas in China are comprehensively analyzed in this paper. China is rich in deep oil and gas resources, but with a generally low degree of exploration and development. There are many promising exploration and development prospects with great resource potential, such as multiple source-reservoir-cap assemblages in the deep formations of superimposed basins in Central and Western China, deep lithological reservoirs and Pre-Mesozoic-Cenozoic buried-hill reservoirs in fault basins in Eastern China, deep shale gas, etc. These are the principal directions for future exploration and development. It is necessary to strengthen research on the accumulation mechanisms and distribution laws of deep oil and gas, as well as the flow mechanisms of deep fluids, and to carry out key technical research, such as deep target identification and prediction based on geophysics, optimized fast drilling under complex formation conditions, and stimulation technologies for complex reservoirs. At the same time, it is also necessary to vigorously promote innovation in management, further enhance cooperation between theory and technology and between enterprises and departments, and to strengthen the management and operation of exploration-development integration and geology-engineering integration. This will provide strong support for the efficient exploration and development of deep oil and gas resources.

With the scale application of the Internet of Things, and the rapid expansion of cloud computing, big data and artificial intelligence technology, the development of information technology has entered a new era of intelligence sharing. The study and construction of a unified digital and intelligent platform, acceleration of the transformation of digitalization and intelligence, and reacting to changes in business requirements efficiently and flexibly, have become urgent tasks for the informatization of exploration and development. The purpose of this paper is to discuss the issues involved, analyze the background and significance of research on PetroChina’s ‘Dream Cloud’ system for exploration and development, introduce the basic principles and overall design scheme of Dream Cloud, elaborate key technical research topics such as the Dream Cloud platform, data link lake, capability of data middle platform, application store, artificial intelligence application, etc., and also summarize construction achievements and application scenario cases of the Dream Cloud platform, data link lake and a series of associated general applications.

The Loess tableland area of the Ordos Basin is a world-famous challenging area for seismic exploration. In order to solve issues in high-efficiency oil exploration and development, such as sweet spots prediction of shale reservoirs, characterization of low-amplitude structures, distribution of small faults and fractures, and real-time geo-steering drilling in horizontal wells, studies have been carried out for many years on seismic exploration and several technologies have been developed. These include: 3D seismic exploration with wide azimuth and broad coverage excited jointly by well shot on loess tableland and low-frequency vibrators; 3D grid tomographic static correction constrained by ultra-deep micro-logging and near-surface absorption compensation on loess tableland, and sweet spot prediction based on comprehensive evaluation of multi-attribute dimension reduction and geological probability, etc. In the Panke 3D “joint excitation of well shot and vibrator” seismic survey area of Heshui County and Ning County loess tableland of Eastern Gansu Province, the average penetration rate is up to 87.4% in shale reservoirs, with seismic geo-steering drilling in horizontal wells. This is more than 10% higher than penetration rates without seismic geo-steering tools. This has become a typical demonstration area in the Changqing oil field, combining seismic technology application with oilfield development. In the Yanchi area of Ningxia province, 3D seismic exploration with low-frequency vibrator and broad coverage technologies has been applied widely. The success rate of reservoir prediction is 72.1%, which is more than twice as high as previous 2D seismic surveys. A breakthrough has therefore been achieved in seismic exploration technologies in the loess tableland area, strongly supporting new discoveries and efficient development in oil and gas fields.

In 2019, the Changqing Oilfield deployed 2 horizontal wells, Chengye-1 and Chengye-2 to carry out risk exploration research tests for shale oil in thick shale interlayered with thin siltstone and fine-sandstone layers (Class II shale oil) in the 73 member of the Yanchang Formation (the Chang 73 member) in the Ordos Basin. High-production oil flows of 121.38 t/d in Well Chengye-1 and 108.38 t/d in Well Chengye-2 have been obtained, which significantly boosts the exploration progress of Class II shale oil. In this paper, cores, thin sections, well loggings and geochemical data from the two horizontal wells, Chengye-1 and Chengye-2, and the pilot well of Well Chengye-1 have been used to study the reservoir conditions and resource potential of Class II shale oil reservoirs in the Chang 73 member. The results show that the reservoir type penetrated by horizontal sections of the two horizontal wells is mainly thick shale interlayered with several thin siltstone and fine-sandstone layers. Thickness of the single layer sand body is 1?5 m. Lateral extension length of single sand body in the horizontal direction is generally in the range 25?50 m and the lateral width of sand bodies is 100?300 m. The distribution area of the single sand body is relatively small. The reservoir types are intergranular pores, dissolution pores, pores, inter-crystalline pores, organic pores and fractures. The intergranular pore radius is concentrated in the range 0.1?3 μm with the maximum of 21 μm. In reservoirs penetrated by pilot sections and horizontal sections, high-conductive fractures are well developed and distributed in an E-W orientation. The porosity of the sandstone reservoirs is 6?12%, and permeability is generally less than 0.3 mD. Shale reservoirs offer poor reservoir performance, with porosity less than 2% and permeability less than 0.01 mD. Using methods such as rock pyrolysis, petroleum ether extraction and dichloromethane extraction, movable shale oil resources in shale and sandstone in the Chang 73 member within a 220 km2 area of the Chengye well block have been evaluated. Preliminary evaluation results indicate resources of (0.692?0.783)×108 t. The distribution area of Class II shale oil in the Chang 73 member in the Ordos Basin is about 1.5×104 km2, and the prospective resources of Class II shale oil in the Chang 73 member are 33×108 t.

As a typical representative of continental fault basins in China, the Jiyang Depression has experienced 3 exploration stages; from structural exploration of large anticlines, through complex oil and gas accumulation belts, to subtle oil and gas reservoirs. At present, exploration objectives in the Jiyang depression are more complex and subtle, which requires a more elaborate degree of exploration research, deployment, and management. By strengthening the dynamic evaluation of the remaining resource potential in the depression, continuously deepening understandings of geological laws, and research and application of exploration supporting technologies, fine evaluation of exploration targets has been carried out in the Shengli Oilfield to achieve continuous and stable increase of reserves in the Jiyang depression. This paper systematically summarizes exploration practice in the Jiyang depression and presents the ‘five fine work and two innovations’ exploration method, which is of great theoretical and practical significance for the exploration and stable development of continental fault basins in eastern China which have experienced a high degree of exploration.

In recent years, a new type of oil reservoir, with reserves of 1 billion tons, has been discovered in the low uplift of Shuntuoguole in the Tarim Basin - ultra-deep fault-karst oil reservoir in the Shunbei area. By deepening understanding of the geological conditions for oil and gas accumulation in the Shunbei area, the constraint on development represented by the fact that karst reservoirs had not been developed in the lower structure positions has been broken. It is also proposed that large-scale reservoirs can be formed by later superimposed buried fluid reformation, mainly due to structure fracturing of strike slip fault zones. The multi-stage activities of strike slip fault zones play an important role in controlling reservoir reformation, trap formation and hydrocarbon migration and accumulation. The hydrocarbon accumulation mode of "multi-stage hydrocarbon supply in Cambrian, deep buried fault-karst reservoir, in-situ vertical migration, mainly late stage accumulation, strike slip faults controlling enrichment" has been established for ultra-deep fault-karst reservoir in the Shunbei area. The main controlling factors of enrichment of the fault-karst reservoir have been presented. As a new type of reservoir, ultra-deep fault-karst reservoir has extended the theory of hydrocarbon accumulation in marine carbonates, confirms the great exploration potential of ultra-deep marine carbonate formations, and is the key field for reserves increase in the future.

The degree of exploration in the1st sand group of the Shawan-1 member of the Neogene (N1s1 1) in the Chepaizi bulge of the Junggar Basin has been generally high, and it is consequently becoming increasingly difficult to tap the potential of the area. A change in the research approach is therefore urgently required to provide support for re-understanding of reservoirs and to promote the search for new exploration targets. Based on comprehensive analysis of cores, thin sections, well logging and seismic data, research into identification standard, formation mechanisms, and seal performance of calcareous barriers inside sand bodies has been carried out, and the petroleum geological significance of the calcareous barriers were analyzed. The results show that calcareous barriers are distributed in the middle and upper parts of sand bodies in the 1st sand group, and that the lithology is mainly fine sandstones with calcite cementation. According to well loggings it is characterized as high Rt, low AC, high DEN, decreasing GR, and SP with feature of a certain return range. The calcareous barriers have a ‘ternary composite’ genesis. The formation of the calcareous barriers is controlled by 3 factors: transition surface of progradation-retrogradation in a short-term cycle; a sedimentary system of shallow braided river delta in an arid environment, and strong calcareous cementation in sedimentary to shallow burial stages. According to analysis of caprock breakthrough pressure, the calcareous barriers can be served as effective caprocks. Guided by these factors, re-understanding of reservoir characteristics based on barrier distribution has been carried out. Several new, and favorable, exploration blocks have been discovered around the reserve area, multiple wells have been successfully drilled, and large-scale reserves have been identified. The exploration performance that has been achieved is promising.

The Wufeng and Longmaxi Formations in the southeast part and the marginal transition zone of the Sichuan Basin are rich in shale gas resources at normal pressure, but face geological difficulties such as poor shale quality, low formation pressure coefficients, and large differences between maximum and the minimum horizontal principal stress. In order to achieve high and stable production, and efficient development, exploration has been carried out on normal pressure shale gas in the Nanchuan- Wulong area. Basic geological research methods, low-cost engineering technology and production management, etc. have been applied, with the result that understanding and practice based on ‘five optimizations’ has been established. The five optimizations are: optimized well locations; optimized trajectory in targets; optimized fractures; optimized cost control, and optimized well management. This program has proved that research on preservation conditions, sedimentary microfacies and tectonic stress is the essential base for selecting and optimizing sweet spot intervals and improving fracturing design, as well as developing innovative low-cost, fast, drilling and completion techniques. Effective fracturing engineering technology is also important for efficient development, and innovative ‘2+3’ management and operation is the guarantee for improving production quality and efficiency.

The Xihu sag in the East China Sea Shelf Basin has distinctive seismic geological features - such as deep layers, serious multiples, thick and heterogeneous sandstone, or thin sand-mud-coal interbeds - which restrict deep exploration. Analysis of the factors controlling the quality of seismic data, as well as key seismic acquisition parameters and actual recorded seismic data, show that the seismic acquisition process in the Xihu sag can be divided into three stages. In the early stage (2D seismic exploration), the objective of seismic acquisition was to evaluate the sag structures and zones. Acquisition parameters developed from ‘short streamers and small seismic source capacity’ to ‘long streamers and large seismic source capacity’. In the middle stage (3D seismic exploration), the objective of seismic acquisition was to evaluate key exploratory blocks. Experience of different acquisition technologies was applied, from conventional 3D acquisition to Q-marine technology and acquisition technology using streamers with dual sensors. In the current stage (secondary 3D seismic exploration of key oil and gas fields), seismic acquisition technologies, such as ‘slant-streamer, wide-band and wide azimuth’ acquisition, ‘high-density and wide azimuth’ acquisition and non-zero offset VSP technology, have been studied and deployed in middle-deep strata in key target blocks. Thus, a series of secondary 3D seismic exploration technologies, characterized by wide-band, wide azimuth, high density and multiple components (2W1H1M), have been developed for seismic acquisition in middle-deep strata.

Due to the limited number of exploration wells and appraisal wells in offshore oil fields, the reserve boundaries of some reservoirs are difficult to prove, which leads to heightened risk in deployment of development appraisal wells or adjustment wells. In order to reduce risk, an evaluation method for progressive development in offshore oilfields, based on dynamic OOIP calculations, is proposed. The method is to calculate dynamic OOIP based on production data, re-check static OOIP, re-define reserves boundaries, and then guide the re-calculation of reserves and the deployment and drilling of development appraisal wells and adjustment wells. In order to improve the accuracy of dynamic OOIP calculations, according to the different parameters and the adaptability of the methods, the material balance method, the modern production decline method, and the water drive curve method are all selected to establish the method system for dynamic OOIP calculation. The linear material balance method for apparent reserves combined with water influx calculation has been introduced, and the modern production decline method, with consideration of limited enclosed water bodies, has been proposed. Referring to the "7.5 rule", the regional formula for dynamic OOIP calculation with Type A water drive curves in the western South China Sea has been established. The Yu Qitai Type water drive curve has also been selected to calculate movable OOIP and technical recoverable reserves in the western South China Sea. This evaluation method has achieved good practical performance in the western South China Sea, guiding the OOIP re-calculation of this kind of reservoir, promoting progressive development and adjustment of tapping potential, and reducing the risk associated with development appraisal wells and adjustment wells.