Oil and gas are the most important primary energy in China or even in the world. The survival and development of the oil industry is determined by such factors as hydrocarbon resources, markets, technology, and socio-political and economic environment, among which technological advance is one of the most active and critical factors. China has become a major producer and consumer of oil and gas in the world, and the developments of China's petroleum industry upstream are highly dependent on the advancement in petroleum technology. China's petroleum industry has established an advanced and complete system for the research and development of theoretical technology and equipment manufacturing, which has supported the sustainable stable yield and the growth of oil and gas output. In the future, China will enter a critical period of social and economic development. The petroleum industry will face great challenges and new technological needs, vigorously implement national innovation strategies, develop new and internationally advanced exploration and development theories and technologies, support the development of the petroleum industry, and protect the national energy security of oil and gas. China's petroleum industry will face major challenges and technological requirements in the future, including:(1)meeting huge oil and gas demand in China's future modernization construction and ensuring the security of oil and gas supply, which requires oil companies to increase domestic oil and gas exploration and development, and further expand oil and gas investment and production along the "Belt and Road" route; (2)achieving long-term stable domestic oil production of more than 2×10⁸t/a; (3)increasing domestic natural gas production to 3 000×10⁸m³/a and maintaining long-term production; (4)developing advanced technologies and equipments for offshore and deepwater oil and gas exploration and development; (5)developing a new generation of technical equipment for petroleum engineering service and realizing digital transformation. The future scientific and technological researches and development priorities in China's petroleum industry upstream include:(1)advanced technologies for greatly enhanced oil recovery; (2)exploration technologies for large gas fields and enhanced oil recovery technologies for complex gas fields; (3)unconventional oil and gas exploration and development technologies; (4)technologies and equipments for offshore and deepwater oil and gas exploration and development; (5)technologies applicable to oil and gas exploration and development along the "Belt and Road" route; (6)new generation technologies and equipments for petroleum engineering service and digital transformation.

On the basis of tracking and investigating the development and application of the gas injection technology for enhanced oil recovery worldwide, this paper summarizes and analyzes the development history of foreign gas flooding technology for enhanced oil recovery and the successful application practice in oilfields such as CO₂ flooding, carbon capture utilization and storage (CCUS), and hydrocarbon gas flooding, top gas injection-assisted gravity flooding and air flooding, and their enlightenment to the development of gas flooding in China. Then it summarizes and studies the characteristic theories, key technologies, and pilot tests in the fields of CO₂ flooding (CCUS), top hydrocarbon gas flooding, oxygen-reduced air flooding, and other enhanced oil recovery technologies by gas injection, applied to the reservoirs dominated by continental deposits in China for over ten years. Based on the development history of gas injection technology in the United States, this paper analyzes the types and potentials of reservoirs suitable for gas flooding in China, gas sources and injection methods, development of matching technologies, pilot test types and effect, and clearly demonstrates that China's gas injection technology is at the key stage of development from industrial test to commercial enlargement and application. In the next 5-10 years, it is expected to increase production to (500-1 000)×10⁴t/a, and it will develop into the most crucial technology for enhanced oil recovery in oilfields following the thermal recovery and chemical flooding technologies, which will play an important role in safeguarding stable oil production in China. Moreover, an analysis is conducted on the the problems faced by China in the development of gas injection technology, such as reservoir conditions, pilot test type and scale, gas source supply, matching technologies and cost, as well as policy support, and gives countermeasures for accelerating technical tests for the key technologies of gas flooding and effective large-scale application from the perspective of nation and main oil companies.

Compared with conventional oil and gas reservoirs, unconventional reservoir rocks are characterized by small pore throats and obvious capillary forces, which greatly affect oil and gas exploration and development. Currently, a large number of methods ignoring the capillary force effect are used to exploit conventional oil and gas reservoirs. However, for self-generated and self-accumulation unconventional reservoirs such as shale oil and gas and coalbed methane (CBM), with the development of nano-pores, there are still difficulties in studying their wettability, capillary force and relative permeability characteristics, and attention should be paid to the application of conventional methods. Taking the tight oil, CBM and shale oil and gas as examples, based on the accumulation theory and the seepage theory in development process, this paper clarifies the role of capillary force in the accumulation and development of unconventional oil and gas. Moreover, it further describes the multiple distribution relationships of oil and water under the original conditions of the reservoir and the corresponding distribution characteristics of fluid pressure. Thus, the seepage mechanism of the wetting and non-wetting phase fluids during water (gas)injection and the snap-off of non-wetting phase can be analyzed and evaluated, providing a theoretical basis for the parameter design of secondary/tertiary oil recovery. Additionally, this paper evaluates the CBM reservoirs with high organic content (TOC), mostly showing water-wet characteristics, and points out that the binding force between water molecules with strong polar and a few polar functional groups in the pore medium is several to several tens of times higher than that between methane and pore organic matter; the wetting angle measurement and capillary force measurement both reflect the action of polar and non-polar attractive force. Thus, although the content of organic matter in CBM reservoirs is much higher than that of inorganic matter, its weak intermolecular forces result in the wettability that tends to be more water-wet. Being different from CBM, the volume content of inorganic matter is much greater than those of organic matter in shale gas reservoirs. Because of the original water-wet environment where most of inorganic pores are developed, this type of reservoir is mostly water-wet. Although the composition of shale oil rock is similar to that of shale gas, due to the complicated composition of oil phase, the surface-active substances in it will affect the wettability of reservoir, and accordingly impact the capillary force. It is more difficult for shale oil to flow than shale gas, and the percolation resistance is noticeable; however, the oil-water capillary force of shale oil is smaller than the gas-water capillary force of shale gas, so it is necessary to quantitatively calculate and evaluate the capillary pressure of the two reservoir systems.

Volcanic oil and gas reservoirs are widely distributed in more than 40 basins in 13 countries around the world, and are one of the important areas of hydrocarbon exploration. After nearly 20 years of accumulation, the research on volcanic reservoirs has achieved great results and become a research hotspot. The research results show that there are 11 classes including 28 types of pores in volcanic rocks, among which primary gas pores, explosive fractures and condensation shrinkage joints are unique types. The combination of primary pores and fractures and secondary pores and fractures forms high-quality reservoirs. Most of volcanic rocks in the basin are medium-low porosity and medium-low permeability reservoirs, and high-and medium-high permeability reservoirs are developed in local area. The porosity and permeability of volcanic rocks decrease with the increase of burial depth. Usually above 3 km, the porosity and permeability of (sed) volcanic pyroclastic rocks are higher than those of lavas, and the opposite is true below 3 km. Generally speaking, various lithologies can develop favorable reservoirs, but in specific blocks, only specific lithologies can develop favorable reservoirs. There are 5 lithofacies and 7 sub-lithofacies which can become favorable facies zones. The distribution mode of reservoirs is restricted by the volcanic stratigraphic unit. For example, lava flow lobe and lava dome form a pattern of "good in upper layers and poor in lower layers". The physical properties of lava flow reservoirs are superior to those of lava dome. The physical properties of reservoirs in the central facies zone of the volcanic edifice are better than those of the proximal facies zone, and those of the distal facies zone are the worst. Most favorable reservoirs are distributed within 200 m below the eruptive interval unconformity boundary or tectonic unconformity boundary. The volcanic reservoir in the basin is the product of comprehensive multi-diagenesis superposition, and has a complicated formation process. Especially, when the volcanic strata have undergone multiple times of uplifting and burial, the evolution process of the reservoir is more complicated. In this process, escape of volatile components, condensing shrinkage, weathering before burial, and devitrification present the unique genesis types of volcanic reservoirs. The soluble components under acidic conditions provide the material basis for alteration/dissolution. The research of the characteristics and distribution laws of volcanic reservoir has basically reached the quantitative stage, while that of reservoir forming mechanism is still in the qualitative stage. Quantitative research of reservoir modeling and pore genesis based on volcanic stratigraphic units should be the focus of the next step.

Self-healing gel is a kind of smart material that can heal itself after being damaged and have the gel strength close to the overall level. This paper systematically introduces the progress in research of the physical self-healing gel based on hydrophobic interaction, hydrogen bond and ionic bond actions and the chemical self-healing gel based on dynamic action of the chemical bonds including imine bond and acylhydrazone bond as well as Diels-Alder reaction; in combination with the application of drilling fluid and the characteristics of different types of self-healing gel, it summarizes the application prospects of self-healing gel in the lost circulation prevention and control, wellbore strengthening and fluid loss reduction of drilling fluid. The self-healing gel can be used as the lost circulation prevention and control material while drilling. After entering the downhole high-permeability matrix and fractures, it will accumulate, and heal itself to form an integral high-strength gel to plug leakage channels. As a wellbore-strengthening material, it can be absorbed and accumulated on the wall of wellbore by hydrogen bond, static electricity and viscous effect. After healing, it forms a high-strength gel layer, which plugs pores and micro-cracks, and strengthens the stability of sidewall. As a material for controlling fluid loss, it can cooperate with clay and polymers. A dense high-strength filter cake is formed on the side wall to reduce the filtration loss of drilling fluid. The research and application of self-healing gel in the field of drilling fluid will promote the intelligentization of drilling fluid technology.

Eight types of the commonly used oil and gas reservoir engineering methods can be summarized as below:material balance equation, production decline equation, waterflood front equation, well testing, modern production decline analysis, numerical simulation, and production planning optimization method. The core impetus is the increasingly complex exploitation targets and the actual needs of sustained and efficient exploitation, as well as the continuous progress of disciplines and techniques involving mathematics, physics, chemistry, information technology, experimental methods,etc. Numerical simulation methods will still be dominant in research of oil and gas reservoir engineering, and will gradually develop in the direction of multi-field, multi-scale, and ground-underground integrated coupled simulation. The application of molecular dynamics, LBM, and micro-and mesoscopic flow simulations in the field of oil and gas reservoir engineering is becoming increasingly important. They are complementary with traditional methods, able to reveal problems in the development mechanism and provide parameters for reservoir numerical simulation. Analytical and semi-analytic methods are simple, easy to calculate, and have clear physical meaning, and will still occupy a place in oil and gas reservoir engineering methods. In addition, with the development of new technologies such as big data and artificial intelligence, reservoir engineering methods based on data analysis have gradually become an important direction.

Based on the reconstruction of global paleo-plate, this study determines the geotectonic characteristics of 4091 geological units in different geological historical periods and the nature of proto-type basins; using 468 key basins as the key calibrations, it restores the types and distribution of paleo and present locations of proto-type basins in 13 geological periods of the Precambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Early Cretaceous, Late Cretaceous, Paleogene and Neogene; further, it explores the evolution of global proto-type basins and its relationship with source rock development and hydrocarbon enrichment. The formation of global proto-type basins is closely related to the evolution of plate tectonics:(1) In the breakup and separation stages of the Rodinia, craton basins and passive marginal basins were mainly formed. (2) Gondwana continental drift and the formation of Pangea controlled the common development of Paleozoic passive continental margin basins, back-arc basins and foreland basins. (3) Pangea breakup primarily controlled the development of rift basins and passive continental margin basins. Global source rocks were mainly developed in passive continental margin basins and rift basins under extensional environments. The development of source rocks is related to continental breakup, sea level rise and extensive transgression, and reached the peak in the Jurassic and Cretaceous. For multi-stage superimposed basins, predicting the distribution of source-reservoir-caprock combination and the favorable areas for oil and gas enrichment by restoring basin proto-types in different stages respectively has important guiding significance for Chinese oil companies' overseas strategic area selection and oil-gas exploration.

Marine shale and terrestrial shale are obviously different in pore structure. The analysis of genetic mechanism based on differences in the rock composition, maturity and organic maceral of marine and terrestrial shale shows that different components in shale have great difference in pore size distribution, and the organic pores account for a high proportion in the range of small pore size. The pore size distribution characteristics of clay mineral are similar with organic pores, while mesopores and macropores are also developed in clay mineral. The small pores of marine and terrestrial shale are mostly provided by organic matter and clay minerals, respectively. Either marine or terrestrial shale mainly has inorganic mineral pores, followed by organic pores. The difference is that the contribution of organic pores in marine shale is higher than that in terrestrial shale, while the contribution of pores in clay minerals of the terrestrial shale is higher as compared with marine shale. The organic pore composition varies at different stages of evolution. In the immature stage, the original cellular pores of vitrinite and inertinite were dominantly developed. In the mature stage, the development of organic pores is the lowest. In the high-mature and over-mature stage, the pores of secondary solid bitumen were predominantly developed. The organic matter of high-mature and over-mature marine shale is dominated by sapropel and solid bitumen, showing the high development of organic pores. The high-mature terrestrial shale represented by Shahezi Formation in Songliao Basin mainly has the organic matter dominated by vitrinite and inertinite, suffering a large loss of original cellular pores, containing a few pores in solid bitumen. In the low-mature terrestrial shale represented by Yanchang Formation in Ordos Basin, the whole development of pores is low due to the filling of pores with sapropel and solid bitumen.

The advanced technology and engineering management mode for rapid and large-scale production increase were summarized, and the integration trend of technological innovation and engineering management in the Middle East oil and gas cooperation was proposed by combing the development and production practical experience of oil and gas cooperation projects in the Middle East. This paper analyzed the investment environment and the characteristics of oilfield development in the Middle East and proposed the concepts and ideas of rapid and large-scale production increase technology. On the basis of multi-modal reservoir heterogeneity characterization technology to optimize reservoir sweet spots, we innovated the integrated production technology of multiple well types and three-dimensional well patterns in giant thick reservoirs, meanwhile we realized rapid-safe drilling and completion technology and key technologies for rapid and large-scale production of surface engineering, finally we established a multi-objective "rapid+scale+benefit" collaborative production model. This paper proposed the practical concepts of reasonable matching between technology and business, efficient collaboration between subsurface and surface, and staged optimization of plans and implementations. Then this paper formed an operating model that combines technological innovation, engineering management and business operations by integrating the development trend of oil and gas cooperation projects in the Middle East. It is an important reference for the oil and gas cooperation of countries along the "Belt and Road Initiatives".

Using scanning electron microscopy, Soxhlet extraction, gas adsorption, nuclear magnetic resonance (including centrifugation) and other experimental methods, a study is performed on the shale in the lower sub-member of the third member of Shahejie Formation (Es₃) in Zhanhua sag, so as to clarify the influence of shale reservoir characteristics on the mobility of shale oil, as well as its action mechanism. Reservoir space such as organic matter pore, intergranular pore, intercrystalline pore, dissolution pore, tectonic fracture and bedding fissure mainly develops in the shale in the Es₃ lower submember of Shahejie Formation in Zhanhua sag. Taking 50 nm and 2 μm as the boundary, the NMR (nuclear magnetic resonance) pore size distribution curves of different lithofacies have obvious three-stage characteristics. The pore volume corresponding to the pore diameter of less than 50 nm is mainly provided by solution pores in calcite, the pore volume corresponding to the pore diameter of 50 nm to 2 μm is provided by intergranular pores, and the pore volume of apertures with a diameter of greater than 2 μm is provided by bedding fissure and tectonic fracture. The characteristics of pore structure and the mineral composition of reservoir jointly control the mobility of shale oil. Shale oil has poor mobility, with the average movable oil saturation of only 21.50%. Movable oil mainly occurs in macropores (pore size greater than 50 nm), and small pores (pore size less than 50 nm) are dominated by irreducible oil. The critical flow pore size of shale oil is about 50 nm. Macropores can not only provide the reservoir space for shale oil, but also facilitate the flow of shale oil. Small pores have a large specific surface area, strong adsorption capacity and poor connectivity, which are not conducive to the flow of shale oil. The mineral fabric macroscopically affects the mobility of shale oil. Increasing the calcite content can increase the brittleness of shale, which is conducive to the formation of fractures and has positive significance for the percolation of shale oil. Due to the larger specific surface area and plugging pore throats, clay minerals are not conducive to the flow of shale oil. The bedding structure not only focilitates the development of bedding fractures and other reservoir space, but also improves the connectivity of shale pores, which is conducive to the flow of shale oil.

Ensuring secure supply of natural gas, which is a complex systemic problem based on the integration of resources, pipeline networks and demands, is critical for maintaining economic development and society stability. Many works have been done in different countries for the reliability analysis of natural gas pipeline networks. However, the reliability assessment method, based on the probabilistic security concept, may suffer from the inherent deficits of underestimating the extreme events with low possibilities but high consequences. This is especially true for large and complex systems. Based on the findings and applications in the areas of power grids, supply chains and transportation systems, this paper proposes the concept of resilience-based supply assurance of natural gas pipeline network, by supplementing the reliability analysis with the concepts of vulnerability and restorability. Then, relevant researches in complex systems, e.g., natural gas pipeline networks and electric power grids, are summarized from the perspectives of status, problem and development. Besides, boosted by the novel technologies, such as Big Data and AI, the resilience-based assurance theory for natural gas supply will become an important theoretical foundation of smart technology for pipeline networks, under the revolution towards intelligentization and marketization.

Staged volume fracturing in horizontal wells is one of the important technologies for the formation of complex fracture networks in reservoirs. To accurately understand the formation mechanism of complex fracture networks and predict the patterns of complex fracture networks is of great significance to the efficient development of unconventional oil and gas resources, and provides a theoretical basis for the design optimization of hydraulic fracturing. Focusing on the formation mechanism of complex fractures in unconventional reservoirs, domestic and foreign scholars have established hydraulic fracturing models according to the impacts of "stress shadow effect" on the simultaneous propagation of hydraulic fractures and those of hydraulic fracturing sequence on the dynamic propagation of multiple fractures, the blocking effect of bedding plane on the longitudinal expansion of hydraulic fractures, and the interactive dynamics between natural fractures and hydraulic fractures; they conducted qualitative analysis from the perspective of numerical simulation. By summarizing the research status at home and abroad and analyzing the existing model in terms of the assumed conditions of model establishment, ideas of numerical simulation model and model limitations, this paper puts forward suggestions for future research directions, which can provide a reference for studying the formation mechanisms of complex fractures by hydraulic fracturing in the future.

Most major petroliferous basins in China have entered a mature exploration period; the remaining oil and gas resources in non-major provenance areas have become more and more important as being the crucial alternative targets for oil and gas exploration. Howerver, the remaining oil and gas reservoirs in non-major provenance areas are highly concealed and difficult to be identified, which severely restricts the exploration and development of this type of reservoirs. Based on the research idea of "Windfiled-Source-Basin" systematic sedimentology, this paper summarizes a set of accurate identification and prediction methods for subtle high-quality reservoirs. This method focuses on the restoration technique of "six paleogeographic factors" based on "Windfield-Source-Basin" ternary coupling, involving the restoration of paleo-wind direction, paleo-wind strength, paleo-wave conditions, paleogeomorphology, paleo-water depth and ancient provenance. Based on the conventional paleogeographic analysis of above six paleogeographic factors, the restoration of paleo-wind field and paleo-wave field further proposed in this paper can help accurately divide the hydrodynamic zoning of the lake, such as the distribution range of wave base, breaker zone and swash-backwash zone. By superimposing hydrodynamic zoning maps and the restoration maps of paleo-water depth, paleogeomorphology and paleo-provenance, we can accurately classify the genetic types of sedimentary bodies, and solve problems on the plane positioning and scale prediction of reservoirs. The "Windfield-Source-Basin" deposition model and the positioning method of ternary coupling high-quality reservoir solve the problems that when using conventional methods, it is difficult to guide oil and gas exploration in non-major provenance and non-large tectonic areas, and realize the accurate prediction of subtle high-quality reservoirs.

After high cycle steam huff and puff stimulation, heavy oil reservoirs are exploited by viscosity reduction chemical flooding, which is an effective alternative method to achieve stable production. As required by the well pattern thickening in the exploitation of heavy oil reservoirs by viscosity reduction chemical flooding after steam huff and puff stimulation, this paper establishes a method for optimizing the location of infill wells with the goal of adjusting the pseudo water breakthrough time from each injection well to production well to be uniform. In view of the uneven distribution of water saturation in the formation after steam huff and puff stimulation, the injection rate equivalent to water saturation at the beginning of injecting viscosity reducer is introduced to the right-hand member of the Buckley-Leverett equation. As considering the temporal change characteristics of viscosity of crude oil during viscosity reduction chemical flooding, a calculation model is set up for the pseudo water breakthrough time, and is solved by iterative time. Taking the variance of the pseudo water breakthrough time from each injection well to the production well as the objective function, a model is established for optimizing the location of infill wells, and is solved using the particle swarm optimization. This paper verifies the accuracy of the proposed optimization method for the location of infill wells by numerical simulations. The research results provide technical support for the rational well pattern deployment during viscosity reduction chemical flooding in heavy oil reservoirs.

The Qaidam Basin is located in the northern part of Qinghai-Tibet Plateau where the Cenozoic tectonic activity is most intense in the whole world. The evolution and reformation of the basin is obviously controlled by the dynamic environment formed by the plateau, and it is a "strongly reformed" basin. Based on the special attributes and dynamic environment of the basin, this study reveals the hydrocarbon occurrence conditions and main controlling factors of the basin. It is one of the main reasons for no important breakthroughs in oil and gas exploration of the Qaidam Basin in the early 30 years that the researchers have not gained a deep understanding of the basin attributes. The abundance and distribution of oil and gas resources in the reformed basin are directly controlled by the hydrocarbon-rich depression (or sag) and the retained source rocks after reformation in the original basin, namely "source-controlling of original basin". A comprehensive study on the restoration of Paleogene original basin reveals that the current southwestern part of Qaidam Basin was once located in the hydrocarbon-rich depression area in the hinterland of the Paleogene basin, and the main source rocks are well preserved; there is a giant hydrocarbon enrichment area of more than 3×10⁴km² around Yingxiongling area, i.e., a key oil exploration area. Due to the strong reformation, the Qaidam Basin has been evolved from a relatively simple hydrocarbon-rich depression structure in the Paleogene to a complex structure including such tectonic units as uplift, sag, fault terrace, and slope. The process and results of the reformation directly control the characteristics, distribution, accumulation pattern and resource scale of oil and gas reservoirs or fields, i.e., reform-controlling reservoir for short. The strong reformation of the basin occurred late and the confining pressure in the deep underground was strong. These distinctive reformation characteristics have more advantages than disadvantages for the generation, migration, accumulation and dissipation of oil and gas. Currently, under the guidance of innovative theories, remarkable results have been achieved in oil and gas exploration, and five types of 100-million-ton-level great oil fields have been discovered successively. The determination of the hydrocarbon enrichment areas in the reformed basin has established the intrinsic connection and prediction basis between the discovered and undiscovered oil and gas reservoirs in the study area, and has opened up a broad exploration field for the continuous discovery of multiple oil and gas fields.

The foreland belt is a very important concept in research of orogenic belt. It refers to the belt-shaped structural area adjacent to the orogenic belt. It consists of foreland thrust belt and foreland basin, and can be divided into peripheral foreland belt and retro-arc foreland belt. Previous researchers put forward the concept of rejuvenated foreland belt when studying the basin-orogen system in central-western China; it is composed of the foreland thrust belt of the rejuvenated orogenic belt and the rejuvenated foreland basin. However, in the Late Triassic, the Longmenshan foreland belt composed of the Longmenshan foreland thrust belt and the western Sichuan foreland basin was very different from these three types of foreland belts in terms of tectonic location, sedimentary characteristics, and geodynamic mechanisms. Based on the previous research results, the study proposes that the Longmenshan foreland belt was a new type of foreland belt in the Late Triassic, i.e., lateral foreland belt. Due to the wedge-shaped geometric characteristics of the Songpan-Garze fold belt, superimposed with the decoupling effect of the deep detachment layer, the orogenic supracrustal material above the detachment layer is decoupled from the lower part, and large-scale lateral extrusion occurs to the southeast, thus leading to lithospheric shortening, thickening and flexural subsidence in Longmenshan area on the lateral margin of the orogenic belt, and forming the Longmenshan foreland lateral thrust belt and the western Sichuan lateral foreland basin. The regional stress state of the Xiaojin arcuate tectonic zone shows a transition from NE-SW compression in the Songpan-Garze fold belt to the NW-SE compression in the Longmenshan foreland thrust belt, which is the strain response to the special stress environment of the lateral foreland belt. The formation and evolution of the lateral foreland belt relies on the special wedge-shaped geometry of the orogenic belt and the detachment layer formed by deep weak sedimentary layers. The former provides an "exit" for the orogenic supracrustal material that is strongly shortened and deformed, and the latter decouples the supracrustal material above the detachment layer from the lower basement. As the orogenic belt continues to squeeze and shorten, the supracrustal material restricted by space cannot be subtracted, and a large-scale displacement occurs in the direction where extrusion may easily occur.

The Early Cambrian was an important life explosion period in geological history. Because of marine transgression, the black shale rich in organic matter are widely developed, and thus has become the most important hydrocarbon exploration strata in the whole world. Although the Lower Cambrian black shale is widely developed in South China, due to such factors as paleo-geomorphology, sedimentary facies, and late tectonic deformation, the source rocks have a large difference in spatial distribution and strong heterogeneity. This will bring risks to hydrocarbon exploration. Based on plenty of previous basic research work, we collect geochemical data of 11 outcrop sections and drilling data of 3 wells, as well as analyze the newly observed and collected samples from a section in South China. This paper systematically studies geological and geochemical characteristics and genetic mechanism of the Cambrian source rocks in the study section through the comprehensive use of major and trace elements, iron components, total organic carbon (TOC), and paleontology. It is found that the Lower Cambrian source rocks are characterized by the sulfuration, reduction and weak oxidation of water bodies from bottom to top, a gradual decrease in TOC, and gradual deterioration of source rock quality. The data of trace elements and iron components reveal the control of the paleo-ocean environment evolution on the formation of high-quality source rocks. Horizontally, the quality of source rocks becomes better from west to east, TOC gradually increased, and the thickness also increases, indicating that sedimentary facies have a controlling effect on the distribution of source rocks, discovering the highest quality source rocks in the rift trough of slope facies and platform facies. Based on plenty of analysis data and comparison of sections, it is believed that the thickness and quality of source rocks are obviously controlled by ancient rift and sedimentary environment. In combination with outcrop and drilling data, this paper predicts the thickness distribution of the Lower Cambrian source rocks in South China, and determines the favorable areas for the accumulation of deep oil and gas and shale gas.

China's marine organic-rich shale has undergone multiple periods of tectonic reworking, and its gas-bearing properties have obvious differences. The preservation condition of shale gas in different stages of tectonic evolution is one of the key scientific issues to reveal the differential enrichment mechanism of shale gas. The studies on tectono-thermal evolution can clarify its thermal evolution history and tectonic uplift-denudation process, providing an evolutionary framework for its evaluation. Using the geothermometers such as apatite fission track, apatite (U-Th)/He and zircon (U-Th)/He, this study conducts the thermal evolution history inversion of the Lower Paleozoic shale in Dingshan area. In combination with the highest geothermal profile reconstructed by vitrinite reflectivity, it restores the differential tectonic uplift process and denudation thickness since the Yanshanian in Dingshan area. In combination with fluid inclusion analysis, it simulates the pressure evolution of the Longmaxi Formation shale in Dingshan area. According to the evolution characteristics of temperature and pressure of the shale in the process of burial-uplift, this paper quantitatively characterizes the variation of shale gas content in different uplifting stages, and establishes the evolutionary framework for "burial-hydrocarbon generation-uplift" of the Longmaxi Formation shale. The analysis shows that Dingshan area underwent different tectonic uplift processes during Yanshanian and Himalayan periods. The uplift process showed periodicity characterized by "rapid uplift in early stage but slow uplift in late stage" with progressive uplift from NW to SE and gradually increasing magnitude of exhumation during Yanshanian period, but overall rapid uplift during Himalayan period. The Yanshanian period is the main period of differential tectonic uplift in Dingshan area. Under the influence of the differential tectonic uplift and denudation, the cooling and pressure reduction process and the shale gas loss process in the Longmaxi Formation shale are significantly different. The differential tectonic uplift in Yanshanian period is the main reason for the gas-bearing zonation of the Longmaxi Formation shale in Dingshan area.

In China, the low-, medium-and high-rank coalbed methane (CBM) resources account for 1/3 of the total resource amount, respectively. The exploration and development of medium-rank CBM has made some progress. Based on analyzing the distribution depth, genesis, and distribution characteristics of CBM in Baode and Linxing blocks of the eastern margin of Ordos Basin, Baiyanghe mining area and Baijiahai uplift of Junggar Basin, and other areas, this paper summarizes the accumulation model of the high-to over-saturation zone of CBM. (1) In the central and western basins of China, the depth and depth interval of the medium-rank coalbeds are very large, providing a huge burial depth space for the development of medium-rank CBM. In addition, the medium-rank CBM is dominated by thermogenic gas, and a certain amount of secondary biogenic gas is supplied to the shallow layers of individual blocks. (2) In view of the low permeability of coal reservoirs in China, exploring high or over saturation gas zones are the key for the efficient development of CBM. Three types of high-to over-saturation CBM zones are secondary biogenic gas supplement type, secondary thermal generation of hydrocarbon supplement type, and deep layer type, respectively. (3) The high-to over-saturation zone recharged by secondary biogenic gas appears in the influence range of shallow freshwater infiltration. The depth of the high-to over-saturation zone recharged by secondary thermal generation of hydrocarbon is related to the depth range of magma intrusion. These two accumulation models appear in local areas. The deep high-to over-saturation zones are common as judged in terms of mechanism, and have been confirmed by exploration practices. (4) To search for the "sweet spot" of deep over-saturation CBM in China during actively exploring the high-to over-saturation zones recharged by secondary biogenic gas and secondary thermal generation of hydrocarbon may become an important development direction for China's CBM exploration and development in the future. (5) Using conventional oil and gas wells to explore deep CBM may be the most effective way to develop CBM in the deep high-to over-saturation zone. For newly drilled conventional oil and gas wells that penetrate through deep coalbeds, attention should be paid to coalbed sampling and coal reservoir evaluation, so as to discover more over-saturation CBM at depth as soon as possible.

The formation and evolution of reservoirs in petroliferous basins are jointly controlled by tectonism and diagenesis. Quantitative evaluation of structural diagenesis is of great significance for deeply understanding the formation and evolution of reservoirs and reservoir quality. By analyzing the connotation of structural diagenesis and the main influencing factors for the formation and evolution of reservoir, this paper proposes that structural diagenetic strength can be used to quantitatively characterize the influence of tectonism and diagenesis on the formation and evolution of reservoirs and reservoir quality. Structural diagenetic strength refers to the degree of influence on tectonism and diagenesis during the formation and evolution of reservoir, which can be quantitatively characterized by the structural diagenetic index. The structural diagenetic strength can reflect not only the influence of time, depth, temperature, pressure and other controlling factors for the diagenetic evolution occurred during burial process on the reservoir, but also the impact of tectonic deformation intensity and its evolution in different structural periods on the reservoir. Quantitative evaluation of the structural diagenetic strength of the deep Cretaceous tight sandstone reservoirs in Kuqa foreland basin shows that the formation and evolution of reservoir is closely related to the structural diagenetic strength. As the structural diagenetic strength increases, the pore volume of reservoir matrix decreases and the development degree of natural fractures increases. From the piedmont structural belt to the frontal uplift belt of Kuqa foreland basin, the structural diagenetic strength successively increases from large to small; the matrix porosity of reservoir gradually increases, while the development degree of natural fractures gradually decreases. The quantitative evaluation method of structural diagenetic strength can provide a new way for the quantitative evaluation and prediction of deep tight sandstone reservoirs.