The Luotan1 well in the Maigaiti slope of Tarim Basin has made a new breakthrough in the Ordovician carbonate rocks, marking the first exploration breakthrough of a new type of Ordovician fault controlled karst carbonate reservoirs in the Maigaiti slope and marking the discovery of an important strategic replacement area in the slope area. Based on regional drilling, logging, seismic and other data, a comprehensive analysis of the laboratory data of well Luotan1 is carried out to further understand the reservoir formation conditions of Ordovician carbonate rocks in the Maigaiti slope. The formation of Ordovician carbonate fault controlled karst reservoirs in the Maigaiti slope is mainly related to strike slip fault activity, and is one of the three main reservoir formation models in the Maigaiti slope. At present, it has been discovered that hydrocarbon in the Maigaiti slope comes from the source rocks of the Cambrian Yuertus Formation, and the basement paleostructure controls the sedimentation and distribution of the Lower Cambrian source rocks. The slope area has three stages of hydrocarbon charging and accumulation: the Caledonian, Hercynian-Indosinian, and Himalayan periods. Hydrocarbon source rocks, paleotectonic evolution, and the faults connecting hydrocarbon source rocks control the multi-stage hydrocarbon accumulation. The fault active stages and fault penetrating layers determine the hydrocarbon enrichment layers and reservoir properties. The Maigaiti slope is characterized by well-developed Ordovician strike slip faults, with an extension distance of over 1000km, which control the distribution of fault controlled karst carbonate reservoirs and hydrocarbon reservoirs. It has clear zoning characteristics on the plane, with a large resource scale and strong deployability, demonstrating huge exploration potential. It is an important practical field for large-scale hydrocarbon exploration discovery and strategic succession in the southwestern Tarim Basin.

Recently, the high-yield oil flow was obtained in the second member of the Paleogene Kongdian Formation (Kong 2 member) in a risk exploration well Cangtan 1 drilled by PetroChina, indicating a major breakthrough in the exploration of deep lithologic oil and gas reservoirs in Cangdong Sag in Bohai Bay Basin. Based on the understanding of Well Cangtan 1, favorable conditions for hydrocarbon accumulation in Cangdong deep subsag area are systematically analyzed to evaluate the exploration prospects and identify the favorable exploration orientation. The study results show that, during the deposition period of Kong 2 member, Cangdong deep subsag area was a subsidence center controlled by Cangdong Fault, providing accommodation for the development of semi deep-deep lake facies source rock. During the lake expansion period, source rock was widely deposited in the deep subsag area, with Type Ⅱ organic matter, high TOC, and mature-highly mature thermal evolution stage (average R_o of 1.3%). The deep subsag area was located at the edge of the lake basin, developing a complete provenance-channel-accumulation system between the basin and mountains, and forming multiple large-scale fan delta reservoirs in the lake basin, which provided favorable conditions for the formation of large-scale lithologic oil and gas reservoirs. The source rock was characterized by early oil generation and expulsion, and continuous oil charging, and the associated acidic fluids and hydrocarbon generation pressurization promoted the development of secondary pores such as intergranular and intragranular dissolution pores. The mature stage of source rock well matched with the development of reservoir, and conventional sandstone oil reservoir and shale oil reservoir were contiguously developed in the deep subsag area. The comprehensive analysis indicates that Kong 2 member in Cangdong deep subsag area has good exploration prospects, and multiple fan delta sand bodies developed in the basin margin have the advantage of near-source hydrocarbon accumulation, which shows a major replacement field for the large-scale reserve increase.

A major breakthrough has been made in the exploration of limy source rock gas in the first member of Maokou Formation (Mao 1 member) in Well DB1H in Da’an area in the western Chongqing, Sichuan Basin, which has important reference and demonstration significance for the intra-source exploration of limy source rock unconventional gas in the Basin. The first horizontal well DB1H was drilled to evaluate the dark limy source rock gas reservoir in Mao 1 member in Sichuan Basin and a high gas rate of 55.6×10⁴ m³/d was tested after acidizing and fracturing. The discovery process of limy source rock gas in Mao 1 member in Da’an area has systematically been introduced, and the resource prospect in Sichuan Basin has been estimated. The analysis of geological characteristics of limy source rock gas in Mao 1 member in Da’an area in the western Chongqing shows that the main lithology is composed of medium-gentle slope facies deep gray-black organic-rich micritic bioclastic limestone, with stable distribution in the region, which is an important marine limy source rock in the Middle and Upper Yangtze region in South China. The hydrocarbon accumulation process of limy source rock gas in Mao 1 member showed an “intra-source integrated evolution” of organic-rich carbonate rock deposition, diagenesis, hydrocarbon generation, reservoir formation, hydrocarbon accumulation and preservation, which had characteristics of “source rock and reservoir integration, in-situ hydrocarbon enrichment, and contiguous gas distribution”. The micro-sized pores in source rock, and the dissolution pores and micro-fracture network system associated with faults served as the main reservoir space, forming two types of reservoirs, i.e., matrix porosity type (primary) and fracture-porosity type (transformed). The hydrocarbon accumulation pattern of “mainly source rock and reservoir integration and enrichment in local structural transition zone after short-distance migration” has been established and the sweet spot evaluation system has been constructed. The key factors for gas enrichment and high-yield production in the new type of limy source rock reservoir in Mao 1 member include the development of organic rich dark limy source rock, favorable paleo uplift, anticlinal tectonic settings at present, and fault-controlled karst and extensional micro-fractures. The estimated resources of limy source rock gas in Mao 1 member are 2×10¹² m³ in Sichuan Basin, which is a new unconventional field for increasing reserves and production in the basin.

The Mesozoic-Paleozoic buried hills in Jiyang Depression experienced multi-stage compression, extension, strike slip and denudation. By taking the eastern Zhanhua Sag as an example, a large amount of well drilling and seismic data is used to identify structural layers, analyze structural evolution and characteristics, summarize structural style of buried hills, and establish hydrocarbon accumulation pattern. The study results show that, controlled by multi-stage tectonic movements after the Late Paleozoic with various directions and natures,buried hills in the eastern Zhanhua Sag experienced four stages of compression, two stages of extension, two stages of strike slip and four stages of denudation, developing three types of buried hills, i.e., high, middle and low buried hills, and forming four categories and nine types of structural styles, including extension, compression, strike slip and denudation. Based on structural styles, residual strata and the overlying strata of the buried hill, three types of hydrocarbon accumulation patterns have been established, which show diversified hydrocarbon sources,enrichment layers and enrichment characteristics. Among them, the hydrocarbon accumulation conditions are the most favorable in the Upper Paleozoic and Mesozoic on the slope of the high buried hill, the Lower Paleozoic in the middle buried hill, and all layers closely adjacent to source rock in the low buried hill, which are the key exploration targets in the near future.

The drilling results have indicated good prospects of shale gas exploration and development in the northern Guizhou area, and a major breakthrough has been made in Anchang syncline in Zheng’an area. However, there are distinct differences in shale gas production among wells, and the reservoir development zone and main controlling factors need to be further clarified. The characteristics and main controlling factors of shale gas reservoir in Wufeng-Longmaxi Formation are systematically analyzed by using wireline logging, mud logging, experimental and lab test data from six vertical pilot wells in Anchang syncline in northern Guizhou, as well as seismic and well production data. The study results show that the rock type in Wufeng-the first member of Longmaxi Formation is dominated by carbonaceous shale. The main mineral composition of the reservoir is quartz, with an average content of 58.66%, followed by clay minerals. The overall brittle mineral content is high, which is 77.19% on an average in the first member of Longmaxi Formation, and shows a significantly lower content in the upper part than that in the lower part. There are multiple reservoir space types in the high-quality shale interval in Wufeng-Longmaxi Formation, mainly including organic pores, inorganic pores and micro fractures. The average measured porosity is 3.46%, and the average permeability is 0.0022 mD, which show a medium-low porosity and ultra-low permeability reservoir. The shale is mainly Type Ⅰ organic matter and high maturity. The total organic carbon content is 4.58% and the total gas content is 4.85 m³/t. The further analysis shows that, in Anchang syncline in northern Guizhou, the favorable oxygen-poor to anoxic sedimentary environment during the deposition period of Wufeng-Longmaxi Formation laid the foundation for organic matter enrichment, a large number of organic matter pores provided a guarantee for reservoir development, and the good preservation conditions played a key role in shale gas accumulation and enrichment. The pressure coefficient is the decisive factor for shale gas production.

Yingxiongling shale in Qaidam Basin has favorable conditions for oil accumulation and enrichment, with oil resources of up to 44.5×10⁸ t. However, the shale has a vertical thickness of more than 1000 m and the shale lithofacies and lithofacies combinations vary greatly, which bring huge challenges to the effective exploration and development of shale oil. The core sections with a length of 578 m from 12 typical wells, including Chai 2-4, Chai 906, and Chai 12 are used to analyze the petrology, organic geochemistry, and reservoir characteristics of Yingxiongling shale. The results indicate that Yingxiongling shale shows distinct characteristics of mixed sediments, with the main mineral composition of calcite, dolomite, and clay minerals, and the sedimentary structure is dominated by laminae with a size of less than 1 cm. Based on the “binary” nomenclature, five types of shale lithofacies are subdivided in the study area, namely, laminated limy dolomite, laminated dolomitic limestone, layered limy dolostone, layered dolomitic limestone, and laminated argillaceous shale. The comprehensive evaluation results of organic geochemistry and reservoir performance of various types of lithofacies show that the laminated dolomitic limestone and the layered limy dolostone are the optimum lithofacies of source rock and reservoir, respectively, with the main reservoir space of dolomite intercrystal pores. The sweet spot comprehensive evaluation results and production performance have confirmed that the interbed of layered limy dolomite and laminated dolomitic limestone is the most favorable source rock-reservoir combination pattern, showing good connectivity among sweet spots in lateral and high heterogeneity in vertical.

In recent years, major discoveries have successively been made in Doseo Basin in Chad, and it has grown to be one of the key basins for overseas petroleum exploration of CNPC. On the basis of previous studies, the latest CNPC well drilling/completion and seismic data are used to systematically analyze the tectonic evolution characteristics and basic conditions for hydrocarbon accumulation in Doseo Basin, which support to identify the favorable exploration fields in the near future. The study results show that Doseo Basin experienced three main stages of tectonic evolution, namely the rift stage in the Early Cretaceous (deposition period of Mangara Formation), fault-depression transition in the middle stage of the Early Cretaceous (deposition period of Kedeni Formation), and depression in the late stage of the Early Cretaceous-Quaternary (deposition period of Doba Formation-Quaternary). As a result, three sets of favorable source rocks were deposited, including the Lower Cretaceous Doba Formation, Kedeni Formation and Mangara Formation. Among them, the lacustrine dark mudstone in Kedeni Formation served as the main source rock, with good organic matter type, high maturity, large thickness and wide distribution area. Multi-set reservoir-cap rock assemblages were developed in the Lower Cretaceous, and multi-type structural traps were formed influenced by multi-stage tectonic activities, developing three types of hydrocarbon accumulation combinations, including self-generation and self-storage type, lower source rock and upper reservoir type, and upper source rock and lower reservoir type. The analysis of the tectonic evolution and the controlling effect on hydrocarbon accumulation indicates that the future favorable exploration fields in Doseo Basin mainly include the northern steep slope zone, the southern gentle slope zone and new strata in the early deposited Mangara Formation.

Associated with the new discovery of marine oil and gas in deep and ultra-deep formations, close attention has widely been attached on the high-quality source rock conditions of marine carbonate rocks in Micangshan area in the northern margin of Sichuan Basin. However, there is a lack of clear understanding on the complex hydrocarbon accumulation, transformation and adjustment processes. The scanning electron microscopy, fluid inclusions, U-Pb geochronology and other means are used to study fluid activity and bitumen characteristics in the Sinian Dengying Formation in Micangshan area, so as to identify multi-stage hydrocarbon accumulation, transformation and adjustment processes. Five stages of fluid activities generally occurred in Dengying Formation reservoir in Micangshan area, i.e., fibrous-fine crystalline dolomite (486 Ma±5 Ma) → medium-coarse crystalline dolomite (413 Ma±5 Ma) → saddle dolomite (268 Ma±8 Ma) → quartz/fluorite/lead-zinc ore (205 Ma±10 Ma) → bitumen (123 Ma±4 Ma). The lumpy, rim-shaped autochthonous bitumen and brecciated, broken allochthonous bitumen were commonly developed in dissolution pores. The spatial comparison shows that from Micangshan paleo uplift, piedmont zone, to the foreland basin, the bitumen abundance decreases as a whole, the autochthonous bitumen relatively increases and the allochthonous bitumen relatively decreases. The further mineral filling sequence study shows that the low-maturity organic hydrocarbon inclusions were mainly developed in fine and medium-coarse crystalline dolomite in the Late Cambrian-Silurian, while the mineral-captured inclusions such as saddle dolomite in the Middle-Late Permian and quartz in the Late Triassic had a relatively high maturity. In summary, the bitumen and inclusion characteristics show that Micangshan paleo uplift and piedmont zone were the paleo oil and gas accumulation center (gas generation and storage center) in the Permian-Jurassic. The primary oil reservoirs were damaged by late tectonic deformation, and the hydrocarbon migration and accumulation center moved to the foreland basin.

The distribution order of oil and gas is a major means to characterize the law of differential hydrocarbon enrichment, providing an important basis for the identification of replacement orientations. The systematic analysis has been conducted, including oil and gas reservoir types, oil and gas properties, degree of hydrocarbon enrichment, hydrocarbon transport system and fault-cap rock conditions, which supports to determine the main controlling factors for the orderly distribution and differential enrichment of oil and gas in Nanpu Sag. The study results show that, from the center to the margin of sub-sags in Nanpu Sag, it shows an orderly change from lithologic oil and gas reservoirs to structural oil and gas reservoirs, the crude oil properties gradually deteriorate, and hydrocarbon gradually enriches in shallower formations. The tectonic activities during the fault and depression periods controlled the distribution and evolution of source rocks, and the tectonic evolution controlled the sedimentary system in the sag and the distribution of reservoir-cap rock combinations and trap type. Among them, three types of reservoir-cap rock combinations below, within and above source rock laid the foundation for multi-layer hydrocarbon distribution. The vertical and lateral transport system and the differential fault-cap rock configuration controlled the process of hydrocarbon migration and accumulation in different structural belts, forming the general law of hydrocarbon enrichment below source rock in the central sag and above source rock in the marginal sag. The study results further reveal the regular distribution of oil and gas in the sag, which provide theoretical guidance and reference for the fine exploration in mature exploration areas.

Gulong Sag in Songliao Basin has good conditions for shale oil enrichment and promising exploration and development potential,and large-scale development tests have been conducted. At present, there is a lack of deep research on the subdivided sequence stratigraphy of Qingshankou Formation, which affects the comprehensive geological study, sweet spot prediction, and exploration deployment of Gulong shale oil. Guided by the theory of seismic sequence stratigraphy and based on the characteristics of relatively stable lateral sedimentation of shale type shale oil, No. 5 test zone of Gulong shale oil is studied as an example, and seismic processing, interpretation (i.e., anisotropic diffusion filtering, sequence recognition and picking), and geology are integrated to identify geological horizons by seismic waveforms,forming a sequence framework construction technology by using seismic waveforms, which has achieved rapid transformation of seismic waveforms into geological sedimentary sequences. In the study area, a total of one secondary, one tertiary, and eight fourth-order sequence boundaries are identified in Qingshankou Formation, and nine thin layers (Q₁-Q₉) are subdivided. The framework characteristics of all thin layers have been analyzed, laying the foundation for shale lithofacies identification and fine prediction of sweet spots. By analyzing four shale evaluation parameters, including TOC, sedimentary structure, mineral composition, and lamina density, a classification standard for shale type lithofacies of Gulong shale has been established based on the subdivided stratigraphic framework, and 10 sub lithofacies have been identified.For Q₁-Q₄ thin layers, three types of sub lithofacies are subdivided, and their plane distribution characteristics are characterized. Based on the above research and the prediction results by using six shale oil sweet spot evaluation parameters such as oil content, brittleness, and physical properties, 11 wells have optimally been deployed in No. 5 test zone, and an average oil rate of more than 10 t/d has been achieved, effectively supporting the beneficial exploration and development of Gulong shale oil in Songliao Basin.

The competitive transfer of oil and gas exploration rights is an important way for oil and gas enterprises to obtain exploration rights blocks, and the evaluation process is characterized by limited data, low level of study and short period. The difficulty in scientifically formulating bidding plans lies in how to comprehensively, rapidly, and accurately evaluate the exploration potential, resource scale, and development economy of transfer blocks in a short term. However, there is a lack of the systematic evaluation method at present. The early study results have shown that the key to the rapid evaluation of competitive transfer blocks includes the optimal selection of rational evaluation parameters and the establishment of parameter standards, and the core of the rapid evaluation of transfer blocks is the comprehensive and quantitative evaluation results. Based on data status and bidding policy of the transfer blocks, nine types of evaluation factors, including data conditions, geological conditions (exploration potential in the region, source rock, reservoir, preservation, trap, and hydrocarbon accumulation assemblage), reliability of resource amount and engineering technology, as well as 18 evaluation parameters and their assignment standards have been proposed, and a rapid evaluation system for competitive transfer blocks has been established. In addition, the petroleum exploration successful probability method has been proposed for comprehensive and quantitative evaluation of exploration potential, exploration risk and engineering technology, as well as the discounted cash flow method and analogy method for economic evaluation, which provide basis for the formulation of bidding plans of transfer blocks. The above method has been applied in some transferred blocks, obtaining bidding plans basically consistent with the actual bidding situation.

The low-resistivity gas layers are observed in HM1 and HM2 sandstone reservoirs in the upper part of the Cretaceous in M Gas Field. Due to the incomplete logging data and lack of density and neutron porosity curves, there are great challenges in gas layer interpretation and evaluation. In the process of logging and well test data interpretation, it is found that there is a good correlation between the bright spot reflection feature in seismic profile and gas-bearing property of the reservoir. AVO technology is applied to process the pre-stack seismic data such as noise reduction and amplitude compensation, and the high-precision AVO profile is obtained with five channels. The analysis of the relationship between amplitude and offset further proves that the bright spot seismic reflection is caused by gas layer, and confirms the feasibility of using seismic data in assisting logging interpretation and gas layer prediction. After effectively scaling and calibrating seismic profile and eliminate lithology factors unrelated to gas enrichment in seismic reflection features by logging data, the direct relationship between seismic reflection features and gas-bearing property of the reservoir is established. By fully tapping and utilizing natural gas information contained in seismic data, the reflection features of seismic profile such as bright spot reflection, pot bottom reflection, and shield-absorption are used to assist logging interpretation, which not only makes up for the lack of logging data, but also further verifies the logging interpretation conclusions. Based on the distribution range of bright spots, the gas-bearing range of HM1 and HM2 layers is precisely delineated, achieving the combination of well and seismic data. In addition, the amplitude variation of bright spots plays a significant role in predicting the high-abundance gas-bearing zone, predicting the thickness variation of gas layers, and estimating the gas-water contact. In the process of gas reservoir interpretation and evaluation, superior results have been obtained by the method of well and seismic data combination, providing a reliable basis for the optimal selection of well location, which has been confirmed by production practice.

Shale reservoir is characterized by physical properties of low porosity and low permeability, and fracturing treatment is often required in shale gas production. The fracability of shale reservoir can be evaluated by brittleness index (BI), and the mineral composition method is the most popular method for calculating rock BI. Based on the mineral composition method calculated core BI value, the non-linear relationship between logging parameters and shale BI has been analyzed by applying the self-learning ability of BP neural network, and then the cuckoo (CS) algorithm with global optimization ability and stability has been used to improve the prediction accuracy and stability of BP neural network, so as to establish a shale BI prediction model based on CS-BP neural network. The CS-BP prediction model has been used to predict shale BI values in wells Y1 and Y2 in the study area, which indicates that CS-BP prediction values have a basically consistent trend with core BI values, showing a good prediction result as a whole. The study results indicate that the cuckoo (CS)-BP neural network based method for rapidly calculating shale BI by using logging data has certain practical value in the study area.