The major discoveries and geological understanding in petroleum exploration since the 12^th Five-Year Plan period are summarized in detail. Four major changes are proposed for future petroleum exploration, i.e., from shallow formation to both deep and shallow formations, from structural to structural-lithologic traps, from clastic rock to multi-lithologic composite reservoir, and from conventional to both conventional and unconventional oil and gas reservoirs. Based on the systematic analysis of the four major petroleum systems in the basin, and combined with the main controlling factors for hydrocarbon accumulation, a total of 13 favorable oil and gas exploration orientations and 3 types of non-oil and gas minerals are identified in Qaidam Basin as in three levels of strategic preparation, strategic breakthrough and strategic deployment. In addition, the main challenges in geology, engineering technology, and management restricting petroleum exploration are systematically summarized and countermeasures are put forward, which provide support for promoting the transformation and development of petroleum exploration, improving petroleum geological theory and technology of strongly transformed basin and the continuous discovery of comprehensive resources in Qaidam Basin.

Unconventional oil and gas reservoirs are closely related but fundamentally different from conventional oil and gas reservoirs. There are four basic characteristics of unconventional oil and gas play, i.e., unreliability of predicting production performance by offset wells in area without well drilling, repeatability of the statistical distribution of the estimated ultimate recoveries (EURs) from wells, regionality of continuous petroleum system, and non-Darcy dynamics of free hydrocarbons. Therefore, the development of unconventional oil and gas faces greater technical and commercial challenges than that of conventional oil and gas, and the concept of resource and reserve management should be innovated in seven aspects, i.e., value management of reserve assets, classification system with economically recoverable reserves as the core, integrated model in the whole life cycle, fracture-controlled volume and well-controlled reserves, heterogeneity of reservoir physical property and production performance, quantitative risk evaluation, and conservative estimation of economically recoverable reserves. An in-depth study on the characteristics of unconventional oil and gas plays and innovative management of resource and reserve will support to promote the exploration and development of unconventional oil and gas resource and improve resource management system in China.

Resource assessment is the basis for decision-making in petroleum exploration, and it is one of the important work for formulating energy development strategy and industry development plan of the government. The difficulties and characteristics of Sinopec’s new round of resource assessment against the new situations are analyzed, and the overall idea and technical framework of resource assessment during the 13^th Five-Year Plan period are demonstrated in detail. As a result, a series of oil and gas resource assessment technologies and software platforms with Sinopec’s characteristics are innovatively developed, including a complete source rock evolution simulation technology from hydrocarbon generation to expulsion and retention, “conventional-unconventional” integrated TSM basin modeling technology, shale oil and gas resources classification and evaluation technology based on maturity and pressure coefficient, “geology-economy-ecology” integrated oil and gas resource assessment technology. Furthermore, on the basis of resource assessment during the 13^th Five-Year Plan period, the key research directions of resource assessment in the future are proposed as follows: (1) 3D hydrocarbon migration and accumulation simulation technology of complex geological conditions and special types of oil and gas reservoirs; (2) Zoning schemes for various types of basins and corresponding resource calculation and splitting technology; (3) Integrated oil and gas resource assessment system based on big data and intelligent platform; (4) Comprehensive evaluation technology of oil and gas co-associated resources.

With the continuous deepening of the state’s policy on management and trading of mining rights and the continuous deepening of the internal circulation of mining rights blocks among oil companies, the asset attribute of oil and gas reserves is more and more prominent, and the management system of emphasizing technology but neglecting value has seriously been impacted. Through the analysis of the current situation and effectiveness of mining rights circulation, the problems of reserve value evaluation existing in the current circulation of mining rights are revealed. In view of the different factors considered by evaluators, the replacement cost method considering the input of reserve acquisition, the discounted cash flow method considering the future income of reserve, and the comprehensive cost method considering both the input of reserve acquisition and the future income of reserve are put forward, forming the value evaluation technology of oil and gas reserves. By taking the value evaluation of oil and gas reserves in M77 block of Changhu Oilfield as an example, the process, results and adaptability of various methods are analyzed, and the feasibility and practicability of this technology are comprehensively verified. In order to promote the marketization of mining rights circulation, work suggestions in five aspects are proposed, including improving the paid use system of mining rights, establishing a trading platform for the transfer of mining rights, exploring the cooperation mode of mixed ownership, strengthening the integrated evaluation of input-output, and building a value-based reserve asset management mode to strive to build a full life-cycle value evaluation system of oil and gas reserves to maintain and increase the value of oil and gas reserves.

Based on the exploration and development results and evaluation of marine shale gas in Sichuan Basin and its peripheral area, the geological conditions and exploration potential of shallow shale gas in Luolong anticline and Laochangping anticline in southeast Chongqing area are studied. By combining wells, seismic, and experimental analysis data, shale gas accumulation conditions and controlling factors of sweet spots are analyzed, and five basic geological characteristics of shale gas in shallow anticline in southeast Chongqing area are identified: (1) The shale reservoir was developed in deep-water shelf facies, showing superior geochemical indexes, with the thickness of high-quality shale of 29-37.5 m, and TOC of 2.01%-6.39%; (2) The shale reservoir has good physical properties, with organic pores developed and porosity of 3.29%-6.58%; (3) The shale formation is dominated by normal pressure, with pressure coefficient of 0.96-1.08 by micro-injection pressure drop test. The total gas content measured by in-situ desorption experiment is 0.66-5.67 m³/t, with the adsorbed gas accounting for 69.97%-78.6%; (4) Shale has high brittle mineral content (quartz content of 30.3%-75.5%), high brittleness index of 59%-65%, shallow burial depth of 880-1100 m, and low in-situ stress (average maximum horizontal principal stress of high-quality shale of 29 MPa), which is favorable for volume fracturing engineering; (5) Although it has experienced multi-stage tectonic transformation, the shale still has certain preservation conditions, and presents an anticline type gas accumulation pattern. On the whole, the fracturing parameters of shale gas in shallow anticline in southeast Chongqing area are low, which is conducive for fracturing engineering. However, engineering technology should be further optimized, and the improvement of single well production and reduction of construction cost be considered, so as to achieve the benefit development.

Based on the sedimentary characteristics of single sand body, the lateral and vertical sand body architecture relationships of meandering river and delta distributary channel facies are established, as well as their corresponding logging identification marks. The characterization methods of reservoir architecture of meandering river and delta distributary channel facies are analyzed and quantitative calculations on the scale of lateral accretion bodies and the occurrence of foreset and lateral accretion layers are conducted by using multiple methods, so as to describe the internal architecture of single sand body. The architecture modeling method constrained by multi-level architecture interface is researched. Different from the conventional methods constrained by grid, multi-level interface constraint and heterogeneous grid technology are integrated in this method to achieve the fine characterization of the architecture level interlayer with a small number of grids. In addition, the conventional capacity splitting methods are analyzed to identify the elements for capacity splitting of single sand body, and a multi-parameter capacity splitting scheme is proposed, which provides technical and theoretical support for the formulation of potential tapping schemes of oil fields in the future.

Influenced by multi-stage tectonic movement, buried hill in Liaodong Bulge in Liaodong Bay Depression experienced complex tectonic evolution. Based on the newly processed 3D seismic data and drilling data, the stratigraphic structure and structural features of buried hill in the south section of Liaodong Bulge are analyzed, and the tectonic evolution and its influence on hydrocarbon accumulation are discussed. The results show that a double-layer structure of the Mesozoic and Archean were developed of buried hill in the south section of Liaodong Bulge, which experienced four stages of tectonic evolution, namely, the development stage of material basis of buried hill (before the Middle Triassic), development stage of buried hill structure (Middle-Late Triassic to the end of the Cretaceous), reconstruction and deep burying stage of buried hill (Paleocene to the end of the Oligocene), and the stably deep burying stage of buried hill (Miocene to Holocene); Controlled by the basement and strong strike slip, buried hill in the south section of Liaodong Bulge was uplifted from the deposition period of the end of the third member of the Oligocene Shahejie Formation (E₂s₃) to the end of Dongying Formation (E₃d). Two types of faults, strike slip fault and extensional fault, were developed in buried hill in Liaodong Bulge, among which strike slip fault controlled the structural framework of Liaodong Bulge and played a key role in the formation of buried hill, while the dual action of extension and strike slip controlled the fracture development in the interior of the buried hill and improved the reservoir performance.

The geological body in ultra-deep formation has high-strength energy accompanied with high pressure, high temperature, and high concentrated stress, which is prone to deformation and instability, leading to the high risk of disaster and accident. Therefore, the study of special geological factors is of great significance in drilling engineering practice of ultra-deep formation. In Tarim Basin, geological factors of the full strata in the drilling process are systematically summarized, and especially the non-target series are finely studied as the target layer. The background and occurrence environment of various geological factors affecting the ultra-deep drilling engineering are analyzed. Furthermore, the internal interaction between drilling engineering and geological factors is revealed by “sedimentary construction, tectonic transformation and sedimentary-tectonism coupling”, and the research and description methods of special geological factors are discussed. The results show that: (1) Compared with the medium-shallow oil and gas reservoirs, 95% of the drilling footage in ultra-deep well is in the non-target series, in which the drilling process directly affects the exploration and development progress; (2) Different from the medium-shallow oil and gas reservoirs, the surface conditions, complex lithology, geological trajectory, formation fluid and extremely high temperature and pressure field in ultra-deep formations are great challenges for drilling operation; (3) The systematic and scientific analysis of the special geological factors in ultra-deep drilling engineering, comprehensive understanding on oil and gas reservoir and an appropriate evaluation on well control safety risk are conducive to risk prevention and well location placement; (4) The analysis on special geological factors of the full strata further supports to construct a bridge between geology and drilling engineering, and promotes the integration of geology and engineering from concept to practice.

Three types of reservoirs are developed in the first member of the Permian Fengcheng Formation (Feng 1 member) in Mabei area with different genesis, i.e., volcanic rock, clastic rock and dolomitic rock. The high-quality reservoirs are mainly high porosity volcanic rock and clastic rock, but the reservoir characteristics and the lateral and vertical distribution are unclear. The comprehensive study on high-quality reservoir of Feng 1 member is conducted by using core, mud logging, well logging and seismic data. The results show that three sets of high-quality reservoirs are developed from bottom to top in Feng 1 member in Mabei area, namely the silty-fine sandstone + gravely sandstone, rhyolitic fused tuff, and gravely sandstone + medium-fine sandstone + conglomerate, and the main reservoir space is composed of vesicles and residual intergranular pores, with good oil-bearing property. The vesicle of the rhyolitic fused tuff is formed by the remelting and sealing of pyroclastic flow. Two sets of clastic rocks are mixed by fan delta front sediments and volcanic rock denudations. Base on genesis analysis, a genetic model of high-quality reservoir of Feng 1 member in Mabei area is established. Furthermore, seismic data are reprocessed and interpreted to identify the three individual sets of high-quality reservoirs, and high-resolution inversion method is applied to effectively predict the distribution of the three sets of reservoirs. The favorable area of clastic rock in the upper section of Feng 1 member is 70 km², mainly distributed in Fengnan 1 and Maye 1 well areas, that of volcanic rock in the middle section is 170 km², and of clastic rock in the lower section is 127 km², mainly in a large area from Well Fengnan 14 to Well Xia 40.

There are abundant shale gas resources in the first member of the Permian Shanxi Formation (Shan 1 member) in Yan’an area. However, the shale reservoir has strong heterogeneity and the geological conditions for gas accumulation are complex. There are abundant shale gas resources in the first member of the Permian Shanxi Formation (Shan 1 member) in Yan’an area. However, the shale reservoir has strong heterogeneity and the geological conditions for gas accumulation are complex. Based on the geological and engineering characteristics of shale gas in Shan 1 member, systematic study and technology research are conducted by using drilling, logging, fracturing, core experiment and well testing data, so as to identify the exploration potential of shale gas in the study area. In addition, key technologies for the exploration and development of continental shale gas are developed. The results show that the interbedding of sand and shale is developed in Shan 1 member with rapid lithofacies changes laterally. The shale is generally gas-bearing, as well as the adjacent sandstone, which is characterized by the mixture of sand and shale and compound gas accumulation. The cumulative shale thickness of Shan 1 member is 25m on average, and the formation pressure coefficient is 0.82. The organic matter is dominated by Type III kerogen, with R_o of between 2.33%-2.85%. Four types of pores and two types of fractures are developed in shale, and the average content of desorption gas is 1.2m³/t. The average gas saturation of the adjacent sandstone is 45%, and the average porosity is 7.2%. The integrated and innovative researches enable to initially develop a series of key technologies, such as “three qualities” logging evaluation of continental shale gas, shale gas reservoir recognition and geosteering while drilling, optimal and fast drilling of horizontal well with low cost, and CO₂ mixed volume fracturing of horizontal well, which strongly support shale gas exploration and development in Yan’an area. Three horizontal wells have been drilled, with drilling time decrease of 11.3%, average thin sandstones penetration rate of more than 75%, and an open flow rate of more than 6×10⁴m³/d.

At present, the management mode of turnkey drilling contract is generally adopted by Sinopec. In terms of the problems in high-risk wells by using this mode, such as long non-production time, long drilling cycle, low application of new technology and weak technical management of oil company, an innovative day rate management system of drilling engineering has been developed with “1 program + 1 core + 2 supporting measures + 1 platform”, which has been applied in Nanchuan block of Sinopec East China Oil & Gas Company and Binchang block of Sinopec North China Oil & Gas Company. By considering the common complex technical problems in the two blocks, such as poor drillability, low ROP, high lost circulation, and severe wellbore collapse, day rate contract management mode and technology are integrated to form a series of drilling engineering demonstration technologies, including the artificial intelligence based drilling speed up technology, measurement while drilling technology in total loss formation, low-viscosity and high shear oil-base drilling fluid system, as well as strong plugging, high inhibition, film-forming, and anti-collapse drilling fluid system, which support to solve the technical problems restricting ROP acceleration. The application in three wells in Nanchuan block of East China Oil & Gas Company and Bingchang block of North China Oil & Gas Company has delivered direct benefit of 335 million RMB, which provide reference experience for the promotion of day rate contract management system of drilling engineering in Sinopec and other domestic oil companies.

At present, the conventional gas logging widely used in domestic oil and gas well drilling operations detects only the light hydrocarbon components lower than nC₅, and has limited capacity to identify reservoir oil-bearing and water-bearing properties. Meanwhile, headspace light hydrocarbon analysis is characterized by great artificial error and long analysis period, which is not applicable for on-site gas detection. Therefore, the GW-OLS online light hydrocarbon logging instrument is developed to continuously and quantitatively acquire the light hydrocarbon data and real time and accurately interpret reservoir fluid property, which achieves the rapid detection and effective analysis of 15 light hydrocarbon components of C₁-nC₈ in 60 seconds by applying the dual quantitative control on drilling fluid extraction and light hydrocarbon component detection, as well as parallel connection design of double capillary columns. In the aspect of reservoir fluid property interpretation, the characteristic chromatogram shape of light hydrocarbon with various reservoir fluid properties is determined, and the online light hydrocarbon chromatogram method is developed which is confirmed by single layer well test results; The oil index-water index interpretation chart is established based on the light hydrocarbon parameters distribution of different reservoir fluids; The online light hydrocarbon multi parameter curve matching method is developewater contact identification of complicated reservoir, and water-bearing property evaluation in condensate oil reservoir, showing promising application prospect.d to identify gas layer, oil layer, and water layer by analyzing curve variation characteristics of key parameters such as Σ(C₁-nC₅ ), Σ(nC₆-nC₈ ), and Σ(BZ+TOL). Field application in Liaohe, Jidong, and Changqing oil fields indicates that the online light hydrocarbon analysis method enables to continuously and rapidly detect the light hydrocarbon and interpret fluid property on drilling fluid samples, which plays an important role in fluid property interpretation of low resistivity and tight reservoir, oil-water contact identification of complicated reservoir, and water-bearing property evaluation in condensate oil reservoir, showing promising application prospect.

The stratigraphic anisotropy is one of the factors that cause the complex logging response of horizontal well. Given the same target layer, the measured acoustic time in horizontal well is usually lower than that in the adjacent vertical well, resulting in a large error of porosity calculated by the measured acoustic time. By comparing the acoustic time of the same section in horizontal wells and adjacent vertical control wells, the acoustic time anisotropy can be better identified. That is, the measured acoustic time of each point of horizontal section is compared with that of the closest control well at the same depth. The results show that the acoustic time of horizontal section is generally lower than that of the adjacent vertical well, and the difference between them is closely related to GR value of the horizontal well, that is, with the increase of GR value in horizontal well, the difference of acoustic time and anisotropy gradually increase. As a result, a new method is proposed to correct the acoustic time anisotropy of Chang 6X layer in Longdong area in Ordos Basin, which shows a good practical application and supports to improve the accuracy of reservoir parameters calculation by logging data in horizontal wells.

Reserve is the core in overseas oil and gas asset acquisition. Due to the different standards applied by various resource countries, the reserve evaluation results vary greatly, which will bring great risks to asset acquisition if they are inaccurately understood. Therefore, the connotation of the international general resource/reserve classification standard and the uncertainty of reserves are analyzed. By taking the actual case study as a link and combining with various challenges in the evaluation of overseas oil and gas assets, “two strengthening” and “two adhering to” are put forward in the evaluation of overseas oil and gas assets, namely, strengthen the study on resource/reserve classification to clarify the reserve connotation; Strengthen the construction of overseas oil and gas reserve database to support the rapid analogy and reserve evaluation; Adhere to the reserve evaluation principle of “uncertainty” to rationally predict resource risks; Adhere to the reserve evaluation principle of “whole life cycle” to objectively understand resource potential.