During the 13th Five-Year Plan period, PetroChina made a number of significant achievements in geological theory and
technological innovation, as well as breakthroughs and discoveries in oil and gas exploration and reserve increase, etc. This paper
reviews and summarizes the company’s oil and gas exploration achievements and theoretical and technological progress during
the 13th Five-Year Plan period and proposes development ideas and strategies for the 14th Five-Year Plan period. During the 13th
Five-Year Plan period, PetroChina highlighted an innovative resource strategy, emphasizing efficient exploration, increasing risk
exploration in new areas and new fields, concentrating exploration on key areas in major basins and fields, and strengthening integrated geological and targeted research. A series of innovative geological theories and understandings were developed and improved,including hydrocarbon accumulation in conglomerate reservoirs in sag areas, hydrocarbon accumulation in large-scale
lithologic reservoirs in shallow water delta, “three paleo” controlling oil reservoirs in marine carbonate rocks, “fault karst” controlling the formation of oil and gas reservoirs in strike-slip fault areas, hydrocarbon accumulation in deep foreland thrust belts,
“four elements” controlling shale oil reservoirs, “three elements” controlling the accumulation and enrichment of shale gas reservoirs,and “three elements” controlling the formation of deep volcanic rock gas reservoirs. A series of exploration and evaluation technologies were developed, such as 3D seismic acquisition, processing and interpretation technology for “double high” and “double complex” areas, drilling and completion technology for deep and ultra-deep formations, well testing technology for deep wells, and volume fracturing technology for long horizontal wells. During the 13th Five-Year Plan period, 34 major breakthroughs were made in the exploration fields of lithologic-stratigraphic reservoirs, marine carbonate rocks, foreland thrust belts, shale oil and gas, mature exploration areas and volcanic rocks in the Sichuan, Tarim, Junggar, Ordos, Songliao, Bohai Bay and other major basins. The historic long-term high-level growth of oil and gas reserves has laid a resource foundation for steadily increasing in oil production and rapid growth in natural gas production. During the 14th Five-Year Plan period, PetroChina will scientifically plan its strategic direction and the focus of oil and gas exploration to promote continuous large-scale increase of conventional oil and gas reserves and rapid development of unconventional resources in six major basins and five fields. The company will accelerate the implementation of large-scale increases in oil and gas reserves, actively prepare strategic replacement areas and major replacement fields, and consolidate the resource foundation for the company’s ongoing high-quality development.

Over the past five years, Sinopec has vigorously promoted high-quality exploration. This paper explains the basis for
development planning for the 14th Five-Year Plan period, summarizes the achievements of China Petroleum and Chemical Corporation (Sinopec) in different exploration fields during the 13th Five-Year Plan period and analyzes new understandings of hydrocarbon accumulation theories and new technological progress. The 13th Five-Year Plan period has been marked by the discovery and cultivation of two 100-million-ton-level oil and gas fields, in carbonate rocks in the Tarim Shunbei oilfield and the Fuling shale gas field in the Sichuan Basin. Six large-scale oil and gas reserves increase positions with billion-ton-levels have also been proved. These achievements have largely been the results of developments in hydrocarbon accumulation theories, ‘sweet-spot’ prediction technology, and low-cost engineering technology in the fields of marine carbonate rocks in the three giant basins of the central and western regions, tight gas and deep (greater than 3500 m in depth) and normal pressure shale gas in the Sichuan Basin, complex and subtle oil and gas reservoirs in the eastern mature exploration areas, and tight oil and gas in clastic rocks in the central and western regions. By comprehensively studying the current status of oil and gas resources, the company has defined development ideas and measures for the 14th Five-Year Plan period. The principal objectives are high-quality development under long-term low oil prices, enhancing exploration efforts, expanding resource types, highlighting exploration across whole plays, invigorating low-grade resources, and accelerating major breakthroughs and discoveries. The goal is to increase proven oil and gas geological reserves by 9.6×108 t and 1.16×1012 m3, respectively. To ensure this goal is achieved, five basic measures are proposed: continuously increasing exploration investment, increasing seismic exploration, strengthening risk exploration, enhancing scientific and technological innovation, and improving engineering technology.

During the “13th Five-Year Plan” period, China National Offshore Oil Corporation (hereinafter referred to as CNOOC)
implemented a national energy development strategy action plan. The plan promoted the integration of exploration, development,
and production in unconventional oil and gas in both domestic exploration and the company’s overseas development business.
New domains and new strata were actively explored, with good exploration results and low operating costs. Proven reserves and
production increased rapidly, creating a new situation in offshore oil and gas exploration. CNOOC has carried out scientific research
on exploration theories and key technologies, and developed a series of innovative understandings of hydrocarbon accumulation
mechanisms for stratigraphic-lithologic, high-temperature and high-pressure (HTHP), deep buried hill, and deep-water
oil and gas reservoirs. Meanwhile, the company has tackled problems in key technologies such as offshore seismic exploration in
mid-deep layers, efficient drilling in complex strata, and practical equipment for offshore exploration. Major exploration breakthroughs have been made in multiple regions of various geological types, including the buried hills of the Bohai Bay Basin, the deep-water area of the Qiongdongnan Basin, the Yangjiang and Huizhou Sags of the Pearl River Mouth Basin, and onshore tight gas in the eastern margin of the Ordos Basin. Recoverable reserves from overseas exploration rights have steadily increased, and an initial strategic plan for the overseas business has been developed. During the “14th Five-Year Plan” period, risk exploration will be strengthened and key technologies for deep formations, deep water high-temperature and high-pressure fields, and lithologic reservoirs studied continuously. Exploration fields and targets are constantly being expanded. The overseas business adheres to the principle of “efficient exploration”, highlighting strategic core areas and striving to obtain more and better-quality reserves.

The PetroChina Daqing Oilfield Company (hereinafter referred to as the Company) is currently facing problems which can be summarized as “insufficient replacement resources, increasing difficulties in petroleum development”. This paper reviews the history of exploration and development of the Company, illustrating its achievements and technological advances in exploration
and development and various business sectors. The major concerns and research directions are summarized, and development
strategies outlined. It is considered that the exploration practice of Daqing Oilfield has been instrumental in improving the general
theories of continental oil generation and source-controlled hydrocarbon accumulation. The company has developed exploration
theories for continental depression lake basins, complex fault depressions, volcanic rocks, and tight oil and gas, with characteristic
associated supporting technologies for petroleum exploration and development. The company faces issues with the expansion and
extension of the scope of petroleum exploration and development, and a series of problems in developing the ultra-high water-cut
Daqing Changyuan oilfield and the difficult-to-recover oil and gas reserves in the periphery of Changyuan oilfield. For this reason,
the company has made it clear that research on supporting technologies for shale oil and carbonate rocks exploration and development should be accelerated, based on improving existing exploration and development technologies. Oil recovery and effective production of difficult-to-recover reserves should achieve the twin goals of effective replacement of resources and increasing oil and gas production. Meanwhile, based on analysis of the major contradictions and challenges, as well as the advantages and potentials of self-development, the Company has proposed a development strategy of “sustainable and effective development of local oil and gas business, large scale and ‘leap forward’ development of the overseas oil and gas business, steady and orderly development of emerging replacement business, and optimization and upgrading development of the service business”. Based on the strategic development objectives of the Company, the “14th Five-Year Plan” for petroleum exploration and development has been formulated, which provides resources guarantees for the transformation, upgrading and development of the Company.

Liuguanzhuang oilfield, located in the Chenghai high slope area on the southern margin of the Qikou Sag, is characterized
by high density, high viscosity, and low saturation crude oil. However, the distribution law of low saturation oil reservoir is
not clear. This type of oil reservoir is difficult to recover and utilize because measures such as thermal recovery and chemical
viscosity reduction generally produce unsatisfactory results. Taking the Liuguanzhuang oilfield as an example, this paper analyzes
the formation mechanisms of low saturation oil reservoir in detail. The study shows that the main controlling factors of the low
saturation oil reservoir in N1g3 include long distance migration of hydrocarbons from the source, strong heterogeneity of the reservoir,and wide and gentle structures. Considered in combination with the enrichment characteristics of the low saturation oil
reservoir, this indicates that the assemblage of Guantao formation unconformity and its overlying basal conglomerate in the high
slope of the Chenghai area, determines the main channel for hydrocarbon migration and also contains the carrier layer for low
saturation oil—an oil-bearing “box”. The hydrocarbon accumulation pattern in the Liuguanzhuang area is dominated by low
saturation oil reservoirs, supplemented by conventional structural and lithologic oil and gas reservoirs, and with “stereoscopic
oil-bearing and integrated as a whole” in the grooves. The development method of “horizontal well + CO2 huff and puff” has been
implemented in a total of ten horizontal wells, with the average production of a single well rising from about 2 t to up to 50 t, and
the recovery factor improving by 7.9%, which is a great benefit for the development of low saturation oil reservoirs in the
Liuguanzhuang oilfield.

In the Lianyuan Sag of the Xiangzhong Depression, Well Xiangye 1 was deployed and implemented to evaluate the geological conditions for accumulation of shale gas in the Permian Dalong Formation. It was the first shale gas parameter well with the Dalong Formation as the target layer. In this study, the geological conditions of shale targets in the Dalong Formation are
analyzed using data from drilling, cores, well logging, and lab test results from Well Xiangye 1, including the sedimentary characteristics,rock minerals composition, organic geochemical characteristics, reservoir physical properties, and gas-bearing properties of the Dalong Formation. The results show that the Dalong Formation shale in Well Xiangye 1 is developed in an anoxic and deep-water platform-basin sedimentary environment, which is conducive to the development of shale and the preservation of organic matter. The thickness of high-quality shale is great (shale thickness is 92.8 m with TOC greater than 2%), there is a high
abundance of organic matter (TOC ranges from 0.41% to 10.47%, with an average of 3.91%), and the thermal evolution degree is moderate (Ro ranges from 1.50% to 1.72%, with an average of 1.58%). The pore structure of the shale reservoir is dominated by mesopores and macropores, with micro-fractures developed. The brittleness index of the shale is high, and the difference in
two-dimensional principal stress is small, which is conducive to the formation of a complex fracture network by hydraulic fracturing.The combination of these parameters indicates that the basic geological conditions are favorable for accumulation of shale gas. However, the preservation conditions are the key factor affecting the gas-bearing properties of the shale. After entering the period of hydrocarbon generation, the Dalong Formation shale in Well Xiangye 1 experienced three distinct phases of tectonic uplift and denudation, which resulted in the current shallow burial depth of the shale and its proximity to the denudation area. Shale gas in synclinal structures was easily able to escape laterally, and the hydrocarbon generation rate of humic kerogen was relatively low; both factors affected the gas-bearing properties of shale in the Dalong Formation. The area far away from the denudation zone, with a wide and gentle structure and great burial depth, and with reverse faults developed in the wings, is more favorable for the accumulation of residual syncline type shale gas.

Since 2015, a series of policies have been issued in China aimed at reform of mining rights. A key element in these polices
is reducing restrictions on access to oil and gas exploration and exploitation. This will inevitably have a major impact on existing
patterns of domestic oil and gas exploration and exploitation. This paper investigates the effect of opening the mining rights
market and changing the mode of transferring mining rights for oil and gas exploration and development activities. Comparisons
are drawn between the modes of mining rights transfer in China and overseas, and policy reform analyzed in terms of its effect in
releasing access restrictions on oil and gas exploration and exploitation. Corresponding measures to help the various parties adapt
to the new policies are suggested. The overall aim is to better embody the spirit of oil and gas mining rights reform, effectively
enhance China’s capacity to secure oil and gas resources, and to realize the sustainable development of state-owned oil and gas
enterprises. To help achieve this, five recommendations are made on two levels, the state and the oil companies. Broadly, these are:establishment of a single unified transfer platform to release exploration blocks regularly in batches, exemption from paying royalties for obtained oil and gas mining rights with compensations, improvement in the procedures for mining rights transfer,
strengthening overall evaluation and selection of blocks within the same basin, and implementing a management evaluation system that is appropriate for competitive transfers.

During “13th Five-Year Plan” period, PetroChina formulated geophysical prospecting technology strategies for each basin and exploration domain according to their varying and increasingly complicated exploration and development objectives.Seismic acquisition design was a particular focus from the outset and process management was emphasized to ensure effective
deployment. Fine processing and interpretation of existing seismic data were conducted to exploit the full potential of data. Research was strengthened to improve problem-solving abilities and resolve bottleneck issues in production. Technical discussions
and workshops to address specific issues in individual basins and domains were encouraged, and training was given to interdisciplinary talents in geophysics and geology to enhance the overall quality of the talent team and the level of technological application.There was a strong focus on essential projects, and lean management was implemented to facilitate robust development. As a result, six categories of geophysical prospecting technologies have been developed and improved and nineteen key technologies formed to strongly support steady growth in oil production and rapid development of the natural gas business. In the “14th Five-Year Plan” period, the focus of petroleum exploration and development will shift to deep/ultra-deep formations, shale oil and gas, very complex surface areas, and more complicated domains. In addition, there will be technological challenges in improving the development of difficult-to-recover reserves and enhancing recovery in mature oilfields. To meet the demands of petroleum exploration development in the new environment, PetroChina will develop high-efficiency, low-cost, and high-precision geophysical technology at three levels—integrated promotion, scientific research, and experiments and pilot testing—in the eight key domains. Priority will be given to new generation geophysical prospecting technologies such as intelligent deep-layer geophysical prospecting technology, reservoir geophysics, and borehole seismic.

Geophysical prospecting technology is an indispensable tool for oil and gas exploration, providing technical support for driving the growth of oil and gas reserves and production in China. After decades of development, the geophysical prospecting technology of Sinopec has its own characteristics in seismic data acquisition, processing and interpretation. Since the “13th Five-Year Plan” period, significant progress has been made in technologies such as high-density seismic exploration, efficient acquisition using vibroseis, deep and ultra-deep carbonate rock reservoir imaging and description, “sweet spot” identification of tight clastic rock, geophysics and engineering integration in unconventional oil and gas, and in software and hardware R&D.These technologies have strongly supported exploration and development in Sinopec’s key oilfields. In this paper, geological problems in Sinopec’s main exploration and development areas are analyzed in detail and the corresponding geophysical prospecting technology requirements in seven major exploration domains described. These include: clastics in the eastern fault basin,deep and ultra-deep carbonate rocks, tight clastic rocks in central-western basins, unconventional oil and gas, piedmont, and offshore areas. Placing Sinopec’s geophysical prospecting technology in the broader context of technical development trends in the industry at home and abroad, this paper proposes a future development direction for Sinopec with three major aspects: “current technology research, future key technology research and development, and ‘neck stuck’ software and equipment development”.This will help to promote high quality development of geophysical exploration technology for Sinopec, which is of great general significance for the rapid development of the geophysical exploration industry in China.

In support of efforts to further reduce the cost of unconventional oil and gas development in China, this paper surveys
recent trends in the use of fracturing proppants in North America and new research on the use of proppants in reservoir stimulation in China and internationally. In doing so, it summarizes the differences in proppant application concepts between domestic and foreign companies. These findings are combined with an appraisal of current unconventional reservoir development in China.The quality of sand from China’s six major quartz sand sources is evaluated and the results of basic theoretical research on the feasibility of use of the various sands reported. Localized sources potential of suitable sand in China are identified and the effect on production and economic benefits of sand proppants generalization is demonstrated by reference to its recent and current application in key oil and gas blocks. The results show that the crushing resistance of domestic quartz sand can reach 4K-5K(equating to approximately 28?35 MPa), and that the quality is equivalent to that of North American common yellow sand. The
national standard for the crushing rate test is reviewed, expanding the application scope of quartz sand. A new principle for the
selection of fracturing proppant is proposed, with improved economic efficiency as the objective. Effective stress analysis shows
that the stress of sand proppant is only 50%?60% of the traditional proppant in horizontal well fracturing. The amount of sand
used in China increased from 650 thousand tons in 2015 to 2.75 million tons in 2019, with an annual cost saving of more than 2
billion yuan. Local sand sources in the giant Junggar, Ordos and Sichuan Basins have also been evaluated and independent sand
plants are being built, with annual production capacity reaching 1.5 million tons, which will enable further substantial cost reductions and efficiency increases in the development of unconventional oil and gas. For example, if the use of sand entirely replaces the use of ceramic proppants in shale gas fracturing, the investment required is expected to reduce to less than 6 billion yuan, a reduction of more than 40%.

The Weiyuan area of Sichuan province is an important block of the national shale gas development demonstration project
in Changning-Weiyuan. The drilling target layer is the high-quality shale in the Lower Silurian Longmaxi Formation. Traditional
mud logging and logging-while-drilling (LWD) methods have encountered difficulties in effectively analyzing and evaluating
shale gas reservoirs in real time, which has led to the low penetration rate of high-quality reservoirs and increased risk during
drilling operations. This paper sets out geological evaluation methods for shale gas reservoirs in horizontal wells based on geological and geochemical logging analysis of large numbers of cutting samples taken while drilling in combination with lab test
data from offset coring wells. TOC evaluation is used to support thin layer identification. The parameters of TOC, adsorbed gas
content, and total hydrocarbon content from gas logging are applied to evaluate the gas-bearing properties of shale gas reservoirs.
The favorable shale gas reservoirs are ranked and screened by combining these properties with the additional parameter of brittle
mineral content. Auxiliary methods for horizontal well geosteering are also described. By constantly analyzing the relative variation
range of key parameters—TOC, calcium (Ca) content, and total hydrocarbon content—drilling engineers can adjust the horizontal
drilling trajectory in real time to control the horizontal section window and landing target. Field application of these methods
has improved the development efficiency of shale gas horizontal wells in the Weiyuan area. This study therefore provides
technical reference for the efficient development of similar shale gas reservoirs.