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.

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.

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.

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.

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.

The use of top high-frequency excitation for drill string unfreezing has the advantages of simple operation, high efficiency and low cost, but the effect of unfreezing operation is seriously affected by the complex downhole environment. Combining the unfreezing device with the drill string and considering the impact of environmental factors, this study establishes a coupled vibration model of the unfreezing device and drill string, so as to reveal vibration response characteristics of the system, and the influence characteristics of such factors as the viscosity of drilling fluid, the depth of free point, hole deviation angle, and working parameters of the high-frequency unfreezing device on the unfreezing force at the free point. Additionally, the optimal range of working parameter is determined according to specific working conditions. The research results show that in the unfreezing operation through high-frequency excitation, the influence factors of unfreezing effect are coupled with each other; according to the actual operating environment and drill string structure, the unfreezing effect can be effectively improved by obtaining the optimal operating parameters.

In this study, the mechanical model of the lateral vibration of sucker rod string(SRS)in directional wells is simplified to a lateral vibration model of the longitudinal and horizontal bending beam with initial bending under constraint conditions of the wellbore. In addition to considering the excitation of the alternating axial load on the lateral vibration of SRS, the model proposes that the curved wellbore is a main excitation for the lateral vibration of SRS in axial motion. Comprehensively considering the excitation to the lateral vibration of SRS in axial reciprocating motion from the curved wellbore and the alternating axial load, respectively, this paper describes the constraints of wellbore to the lateral vibration of SRS when applying the elastic collision theory, and establishes a mathematical model of the lateral vibration simulation of the SRS with initial bending under constraint conditions of the wellbore. Based on the simulation model of lateral vibration of SRS in directional wells, a mathematical model is established for the point arrangement optimization of centralizer. Using the Runge-Kutta method, this study realizes the simulation calculation of the lateral vibration of SRS in directional wells; Using the loop iteration method, it realizes the point arrangement optimization of centralizer. The results show that:1the simulation results are consistent with the actual situation of the oilfield, thus verifying the applicability of the model; 2the dangerous point of SRS and tubing wear is the build up section of borehole and the pressure section of SRS. The rod-tube contact force in the build up section of wellbore is relatively large, and the rod-tube collision in the pressure section of SRS is severe; 3after optimizing the centralizer configuration, the rod body and coupling do not contact with the tubing, and the maximum rod-tube contact force of the centralizer is within the allowable contact stress, ensuring the working life of SRS.

To study whether there is an analytical solution to the design equation set of three-dimensional arc-shaped well trajectory and how to solve it effectively, this paper uses the elimination method to deduce an unknown number from the multivariate nonlinear equation set which satisfies a characteristic polynomial equation, and proves that the approximate analytical solution of the equation set can be calculated from the analytic formula including the real roots of characteristic polynomial equation and the known design parameters. If the polar polynomial is not identically vanishing, when the degree of the characteristic polynomial does not exceed 5, if there is a solution, it is an analytical solution. Otherwise, it is a numerical solution. The authors explore the methods of applying polynomial addition, subtraction and multiplication in computer programming using C++ classes, propose the real root insulating algorithm for the real number roots of a polynomial, and quickly determines the calculation scheme for all real roots of polynomials by dichotomy. The proposed method is rigorously deduced in mathematics, and the calculation scheme is simple and robust. It has application value in the three-dimensional well trajectory design and directional control of intelligent drilling.

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.

There are many factors affecting the system efficiency of pumping units in the middle and late stages of oil recovery and the data is complex and featureless, resulting in the poor regulation effect on system efficiency. Based on the big data mining technology, taking an oil production block in the central Daqing oilfield as the research object, the paper reveals the changing law of system efficiency by combining surface data and downhole data, and using typical clustering algorithms for block data, the clustering algorithms of k-means and DBSCAN are used to analyze oilfield data. First, the optimal k value is determined by the ratios of the inter-cluster and intra-cluster error square sum to the total error square sum, and the data set is clustered using the k-means algorithm. Then, the data set is further clustered using the DBSCAN algorithm by setting different Minpts and ε values. By visualizing the clustering results, this paper compares the differences between the two clustering methods, and finds that the k-means algorithm is more consistent with the cluster analysis results of the central Daqing oilfield, and provides the representation characteristics of low-efficiency wells in the block according to the k-means clustering results when k=4, thus providing guidance for the regulation of system efficiency for wells in the block.

The physical model experiment of steam distribution in horizontal wells is an effective means to simulate the actual steam injection process in the oilfield. Domestic and foreign scholars have carried out different experimental studies on the steam distribution effect of horizontal wells, but at this stage, few researches focus on the influence of the steam distribution structure of horizontal wells on the steam distribution effect. By constructing a three-dimensional experimental model, and designing the steam distribution structure of steam injection wells, the authors carried out three-dimensional steam injection experiments under different steam distribution structures. The experimental results show that different steam distribution structures have a great impact on the steam distribution effect. The steam distribution effect is the worst in the experiment using slotted tubing string, steam channeling occurred earlier in reservoirs near the steam injection well; and occurred later in experiments using the uniformly-perforated tubing strings, and the densely-perforated tubing strings near the toe end, the production range of reservoirs is wider. When performing the steam distribution experiment near the toe end, as the steam distribution volume increases, the steam will flow back. When the steam distribution hole is evenly distributed along the direction of horizontal well, although the steam can be distributed more evenly in the early stage of steam injection, with the increasing of steam injection volume, the steam will be preferentially distributed from the heel end of horizontal well, and the steam distribution volume at the heel end is always the largest. The steam distribution volume in front of and behind the horizontal well can be effectively changed and the steam distribution effect will be optimized by adjusting the distribution density of steam distribution holes in front of and behind the steam injection well. It will provide theoretical support for the optimization design of steam distribution structure of steam injection wells in oilfields, so as to achieve the goal of effectively improving the steam distribution effect and uniform reservoir production.

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 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".

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.

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.

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.

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.

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.

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.

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.