Two sets of source rocks， Wenchang Formation and Enping Formation， were developed in Baiyun Sag of the Pearl River Mouth Basin during the rifting period. Through 3D seismic data and deep drilling analysis， it is believed that axial braided river delta system， fault controlled fan delta system， braided river delta system in the north gentle slope zone and shore shallow lake medium deep lake system in the basin are developed during the rifting period of Baiyun Main Depression. In the early stage of rifting， many groups of NE trending fault terraces are developed and the landform is characterized by many ups and depressions. The provenance mainly enters the depression from the east to the west， forming multi-point source water systems and developing multi depressions to generate hydrocarbons； In the middle of rifting， due to the extension of detachment faults， the lake basin expanded， and the Panyu low uplift in the north was strongly uplifted， forming a large delta system and a large lake basin with gentle slopes； In the late rifting period， the lake basin was dominated by depression， and coal type and transgressive source rocks were developed under the influence of South China provenance and transgression from south to north. According to sedimentary facies and geochemical indicators， the source rocks in Baiyun Sag can be divided into three types： Type I-II₁ source rocks of middle-deep lacustrine facies in Wenchang Formation， Type II₂ source rocks of shallow lacustrine facies in Wenchang Formation and Types II₂-III source rocks of shallow lacustrine facies in Enping Formation. The hydrocarbon generation potential of different types of source rocks is different， and the middle-deep lacustrine facies source rocks in Wenchang Formation are the best. The element geochemical indicators reveal that the overall hydrocarbon generating environment of the lake basin belongs to freshwater to brackish water， reducing to strong reducing water environment， while the paleontology reveals that the oil generating parent material of the lake basin is Huxiang planktonic algae and terrestrial plants， and the organic matter of high-quality hydrocarbon source rocks mainly comes from planktonic algae. In a word， the detachment fault activity and sedimentary system of Baiyun Sag control the development thickness and scale of hydrocarbon source rock， and the high-quality water environment controls the formation of high-quality hydrocarbon source rock. Therefore， the source rocks in Baiyun Sag have geological conditions of large thickness and wide distribution， and have great resources and exploration potential.

The third member of Weizhou Formation of Oligocene is the most important reservoir in Haizhong Sag， Beibuwan Basin， so it is very important to study the distribution regulation of depositional systems for oil and gas exploration in the area. Based on the fine description of drilling cores in the study area， combined with the characteristics of logging facies， seismic facies and seismic attributes， the depositional facies were determined and the sedimentary models in faulted lacustrine basins is established. The results show that the discal-sheeted reflection， progradational reflection and channel filling reflection are the most sand-rich seismic facies in the third member of Weizhou Formation； There are four types of depositional facies： Shore-shallow lacustrine facies， braided river delta， fan delta and alluvial fan in the third member of Weizhou Formation； Under the background of shore-shallow lake and controlled by the half-graben lake basin structure with gentle southern and steep northern slope， the Haizhong Sag as a whole shows the sedimentary characteristics of north-south differentiation， which is manifested by the development of braided river delta in the gentle slope zone in the south， braided river deltas and fan deltas was developed in the north； At the same time， factors such as slope break zone， fault style and gully ancient landform control the deltas from three different directions， and the provenances of Qixi uplift in the south mainly develop braided river deltas. The plain and front are divided on the plane by the slope break zone， and the source of the Weixinan low uplift in the middle of the Beibuwan Basin is controlled by the fault to develop braided river deltas and fan deltas in the west， the sediments from Wanshan uplift in northwest formed a braided river delta by long-distance transport in the edge of Lake basin in the northwest of the study area.

In recent years， deep shale gas exploration breakthroughs have been achieved in the Wufeng -Longmaxi formations in the complex tectonic region of the Sichuan Basin and southeastern margin， showing good prospects for deep shale gas exploration and development. Based on the data from drilling wells and experimental analysis tests， the study of deep shale gas enrichment characteristics is carried out in the Nanchuan area of the complex tectonic region of the southeastern Sichuan Basin margin， focusing on the role of changes in the formation environment such as formation temperature and pressure on deep shale gas enrichment. The study concludes that： （1） The dominant sedimentary phase zone is the basis for hydrocarbon formation in shale gas reservoirs. The Wufeng Formation - the first member of Longmaxi Formation in the study area was formed in a deep-water shelf sedimentary environment with high-quality shale development， which has good material conditions for the formation of shale gas reservoirs. （2） Organic carbon content controls the degree of development of nanoscale organic matter pores， and the high-pressure-ultra-high-pressure environment is conducive to the maintenance of pores and it plays a positive role in improving the physical properties of deep shale. （3） Deep shale gas has the typical geological characteristics of high temperature， high ground stress， and exceptionally low permeability. The influence of temperature on the adsorption capacity of shale is more obvious than that of pressure， and the deep shale gas is mainly free gas. High pressure can slow down or inhibit the gas flow， which is beneficial to shale gas preservation. （4）The changes of temperature and pressure have complex effects on gas diffusion. High temperature will increase the diffusion coefficient of gas， aggravate the migration and escape of gas， while high pressure can slow down or inhibit the flow of gas， which is beneficial to the preservation of shale gas. （5） The burial depth and pressure coefficient show a certain positive correlation， and the burial depth has a more significant effect on the pressure coefficient of syncline shale gas， indicating that the preservation conditions of deep syncline shale gas reservoirs have a tendency to become better. The residual syncline core with larger depths， inner-sag uplift， and slopes with reverse faults can be favorable targets for shale gas exploration in complex tectonic zones.

Transitional shale gas layers are widely distributed in China， whereas no significant exploration breakthrough has been made so far. In this paper， characteristics and gas-bearing mechanisms of transitional shale gas reservoirs were investigated and analyzed in detail， aiming to clarify shale gas accumulation mechanism of transitional facies and provide theoretical support for the selection of favorable intervals. Transitional shale gas layer is characterized by thin single layer thickness， rapid lithological change and poor kerogen type. Due to the limited numbers of OM nanometer-scale pores， shale pore space is dominated by pores and fractures related to clay minerals. The measured gas content is well consistent with theoretically calculated gas content for marine organic-rich shales. However， actual measured gas content is far lower than the theoretical calculated gas content for transitional shale gas reservoir. The main mechanism are summarized to be that （1） high hydrocarbon expulsion efficiency of “sandwich” space structure of sandstone-shale-coal association gives rise to most natural gas into nearby sandstone， and （2） high water saturation results in insufficient storage space for free gas in shale reservoir. Unlike marine shale gas， natural gas in transitional shale reservoir is primarily dominated by adsorbed gas in kerogen， and free gas is generally low. The favorable lithofacies types are organic-rich siliceous/calcareous shales. Multiple layers of siderite-bearing shale/siderites are developed vertically and are continuously distributed horizontally in transitional strata， particularly in flat-lagoon facies. It is easy to form “micro-trap” to storage gas in siderite-bearing shale， and siderite-bearing shale has strong sealing properties due to low porosity， low permeability and high breakthrough pressure. This property can form overpressure and trap shale gas inside the shale， which provides a new research perspective for the optimization of vertical favorable intervals， as well as exploration breakthrough in transitional shale gas. Further research should strengthen the systematic sedimentological study of transitional facies， reveal shale gas occurrence state and dynamic transformation， optimize favorable interval evaluation system and clarify the feasibility of coal-measure gas commingled production.

In order to clarify the influence of organic matter and mineral composition on the pore structure of shale reservoir in the seventh member of Yanchang Formation (Chang 7 Member), Ordos Basin, the pore structure characteristics of Chang 7 Member shale reservoir were analyzed by Argon Ion Polishing-Field Emission Scanning Electron Microscopy (FE-SEM) and Low-pressure Aitrogen adsorption (LP-N2A), and the controlling factors of pore structure were analyzed in combination with whole-rock mineral composition and organic geochemistry experiment. The results show that the Chang 7 Member shale mainly develops intercrystalline pores of clay minerals and intergranular pores, and a few organic matter pores, dissolution pores and microfractures can be seen. The LP-N2A isotherms of shale are all type Ⅱ isotherms, with H₃ and H₄ hysteresis loop characteristics, indicating that the mesopore are relatively developed, and the pore morphology is parallel lamellar and "ink bottle" shape. The pore structure of shale is controlled by the organic matter, clay minerals, quartz, feldspar and pyrite. The clay mineral phase transformation forms a large number of micropores and mesopores between the mineral crystal layers, which is the main source of pores in shale in the study area. Liquid hydrocarbon, solid asphalt and monoidiomorphic pyrite generated from organic matter filled the pores of inorganic minerals, which reduced the pore space of shale in Chang 7 Member to a certain extent. These results can provide a new cognition for understanding the pore structure characteristics and controlling factors of Chang 7 Member shale.

The formation of high-quality source rocks is affected by many factors. It is of great significance to recognize the differences of controlling factors of different types of source rocks for accurately predicting the "sweet spot" of shale and improving the efficiency of unconventional oil and gas exploration. In this paper, we selected four source rocks （Es₃^z， Es₃^x， Es₄^cs， Es₄^cx） in the Paleogene Shahejie Formation, Niuzhuang Sag of Dongying Sag of Bohai Bay Basin, and carried out thin section, pyrolysis, and major and trace elements analyses to discuss the differences in controlling factors of source rock formation in each member. Es₃^x and Es₄^cs source rocks, which are developed in deep-water brackish and deep-water brackish environments, respectively, have higher TOC and are dominated by type Ⅱ₁-Ⅰ aquatic organic matter. Es₄^cx and Es₃^z source rocks, which is deposited in shallow water brackish evaporation and shallow water brackish environments, respectively, have lower TOC and are dominated by typeⅢ-Ⅱ₁ terrigenous organic matter. The level of paleoproductivity is as follows: Es₄^cs> Es₄^cx > Es₃^x > Es₃^z.Source rocks in each member have differences in organic matter, environment and productivity. The enrichment degree of organic matter is proportional to paleoproductivity, salinity and water depth, and is not affected by redox conditions. The high productivity is the key factor, when productivity is higher （Es₄^s and Es₃^x），the further enrichment of organic matter is obviously controlled by the environment: under the deep water and desalination environment （Es₃^x）， salinity is the main restriction factor of the formation of organic matter; In the saltwater environment（Es₄^cs），the controlling effect of water depth is prominent. In the low productivity shallow water desalinated lake basin （Es₃^z） environment, the paleoproductivity, salinity and water depth have obvious control on organic matter development, which reflects the common control of multiple factors on organic matter and the differences of controlling factors on organic matter enrichment in source rocks of different strata. Therefore, in addition to productivity and preservation conditions, attention should also be paid to environmental factors such as salinity and water depth, as well as the coupling between multiple factors, which is of great significance to deepen the understanding of the development law of source rocks and guide unconventional oil and gas exploration.

The research for tectonic setting， material source and paleoenvironment of Keluke Formation in the Lower Carboniferous remains weak， although hydrocarbons have been discovered in the formation of Ounan Depression， which is located in the east of northern Qaidam Basin. The study about element geochemistry of the C₂k fine-grained deposits from the Baishugou outcrop in the northeastern depression has been investigated； and the results indicate that the depression should be one part of the back-arc rifted basin， which developed in the tectonic setting of active continental margin while the Animachen ocean crust subducting northward during C₂k. Terrigenous detrital materials were provided into the depression from parent rocks of the North Qaidam Orogenic Belt in the south， which were dominated by acidic igneous rocks. The pillow basalt were erupted in the Zongwulong Rough to the north of the depression， which were easily eroded to the dissolved silica， carried by the upwelling into the depression and subsequently transformed to the biogenic silica by thriving siliceous plankton organisms. The C₂k stage was in the phase III of the late Paleozoic ice age and three interglacial warming events （periods A， B and C） have been identified， when the temperature increment causing the transgression for the glacial ablation， palaeobathymetric increasing， anoxic event and salinity growing for the seawater recharge and heating evaporation. The intensity of temperature rise and the extent of sea level rise in the warming period B were stronger than that in the periods A and C， when the sea level reached the maximum sea surface and depositional environment was weakly-reductive in the study area during C₂k. The C₂k paleoproductivity in the outcrop was composed of terrigenous plants and ocean aquatic organisms such as siliceous organism， respectively from the directions of North Qaidam Orogenic Belt and Zongwulong Rough， which are the typical mixed terrestrial and marine organic matters. The input intensity of ocean aquatic organic matters reached the maximum in the warming period B and it was primary influenced by the terrigenous organic matter in the other periods. This study has significance for comprehending the tectonic-sedimentary-palaeogeographic evolution process and mechanism of organic matter enrichment in the Carboniferous of the Qaidam Basin.

Benxi Formation of Carboniferous in the Ordos Basin has unconventional energy sources， and its sedimentary environment is complex and interactive. Therefore， through the analysis and testing of core samples of typical wells in eastern Ordos Basin， based on the observation of core samples，this study reveals the paleoclimate and the palaleobathymetry environment of shale in Benxi Formation， and discusses the control of sedimentary facies characteristics on the shale development. The results show that the salinity of the palaeobathymetry of Benxi Formation gradually decreases from smaller to bigger， and the salinity of the coal seam water at the top of Hutian Member to Jinci Member gradually changes from saline water to saline water reclamation； redox sensitive parameters（Th/U）of Benxi Formation decrease first and then increase from lower to upper. Hutian Member， Pangou Member and Jinci Member are anoxic environment， oxygen poor anoxic environment and weak redox environment， respectively. The study of ancient water depth（Rb/Zr）shows that the ancient water depth of Benxi Formation changes periodically from lower to upper， and then gradually back to lower again； CaO/（Al₂O₃+MgO）， CIA and other paleoclimate indicators reflect that Benxi Formation has a hot and humid climate. We compared the mineral composition and lithologic combination characteristics of the mud shale under different sedimentary backgrounds of Benxi Formation in eastern Ordos Basin， and further divided the facies into swamp deposit， lagoon-tidal-flat-barrier island mixed sediments， and lagoon-tidal-flat-barrier island-swamp mixed sediments were developed in Hutian Member， Pangou Member and Jinci Member respectively.

On the basis of characteristics of shale reservoir formation， such as lithology and mineral composition， organic geochemistry， reservoir characteristics， gas-bearing characteristics， combined with structural style and burial depth， faults and fractures， top and floor cap rocks， reservoir pressure， a comprehensive characterization of the Niutitang shale is performed. The results indicate the Niutitang shale has high TOC， high R_O， brittle mineral contents and methane sorption capacity. The main pores of shale minerals include mud particle pores， bedding cracks， interlayer cracks， which are large in number and mainly primary， and have a significant impact on the porosity and permeability of the reservoir. The total gas content of shale has a significant positive correlation with porosity， specific surface area and TOC， and is inversely proportional to clay mineral content. So the contribution of porosity and specific surface area to gas content of shale is greater than that of clay mineral content. From the perspective of preservation conditions， the gentle anticline and saddle structural strata sandwiched by the anticline in the study area is relatively slow， the burial depth of Niutitang Formation is moderate， and it has good roof and floor caprock， which is conducive to the preservation of shale gas. But poor sealing， strike slip and high angle fracture fault are not conducive to preservation， which will destroy the preservation of shale. In addition， reservoir pressure does not play a decisive role in preservation conditions， and there is also industrial value of shale gas accumulation in low-pressure and atmospheric pressure formations. Finally， a valuation index system of preservation conditions is put forward and the comprehensive favorable areas for shale accumulation in the study area are optimized.

An important set of source rocks is developed in Fengcheng Formation of Lower Permian in Junggar Basin. This research took full advantages of ICP-MS， XRF in the measurements around major elements and trace elements， along with biomarkers of saturated hydrocarbons in 25 source rock samples from Fengcheng Formation in Well Maye 1， Mahu Sag. Based on previous research results， the geochemical characteristics and sedimentary paleoenvironment of the source rocks of Fengcheng Formation in Mahu Sag were comprehensively studied. The research demonstrated that the sedimentary evolution of Fengcheng Formation can be divided into five stages. The first and second stages （sedimentary period of Feng1 section） were mainly defined as evaporation and salinization. In the third and fourth stages （sedimentary period of Feng2 section）， calcium and magnesium carbonate deposits， as well as sodium carbonate deposits were salinized and alkalized under the influence of hydrothermal action. In the fifth stage （sedimentary period of Feng3 section）， tuffaceous mudstone and terrigenous clastic rock were deposited under the condition of volcanic activities and damp climate， while the desalination took the role of primary reaction. Accordingly， the water depth of the lake basin developed in Mahu Sag changed periodically and became gradually shallower in general. The corresponding paleo-salinity evolution characteristics of lake water were light-semi-saline-saline-semi-saline-light， while the paleoclimate evolution features are semi-arid-humid-semi-arid-arid-semi-arid， but the semi-arid-arid climate performed generally. The grain size and sedimentary tectonic changes of clastic rocks in Fengcheng Formation can be used as an appropriate environmental index， while the deposition of Fengcheng Formation was controlled by volcanic activities and paleoclimate， as the preservation of organic matter was closely related to paleo-bathymetric and redox preservation conditions of water body. The arid climate results in a large amount of evaporation of water， promoting salinization， while hydrothermal action provides a general series of nutrients， and promotion of the alkaline lake.

In order to find out the geological characteristics and enrichment law of continental shale oil and gas， the geological characteristics and enrichment law of Lianggaoshan Formation shale oil and gas reservoir in Fuling area were studied by means of whole rock mineral X-ray diffraction， organic geochemistry， argon ion polishing scanning electron microscope， helium porosity， field gas content test and seismic pressure coefficient prediction. It is pointed out that Lianggaoshan Formation shale has the characteristics of high mud to ground ratio， high GR， high TOC and high gas content. It is proposed that the enrichment and high yield of continental shale oil and gas in Fuling area are mainly controlled by four factors： （1） Semi-deep lacustrine shale distributed in large area is the basis of hydrocarbon generation and reservoir control of shale oil and gas； （2） The appropriate degree of evolution controls the enrichment and accumulation of continental shale oil and gas； （3） Good preservation conditions are the key to the enrichment and accumulation of shale oil and gas； （4） The development of micro fractures with different scales is conducive to the high production of continental shale oil and gas. Among the influencing factors， the preservation conditions and the development of microfractures have the greatest impact on enrichment and high yield.

Corresponding to the transitional period of the earth system from Late Permian to Early Triassic times （referred to as the P-T transition period）， the Mahu Sag of the Junggar Basin experienced a transition from a foreland basin to a large depression lake basin， with the development of two sets of unconformities（T₁/P and P₃w/P₂w） and two sets of lowstand deposits， the Upper Wuerhe Formation （P₃w） and Baikouquan Formation （T₁b） that host a series of large or giant conglomerate oil fields. For the two third-order sequence boundaries T₁/P and P₃/P₂， two types of slope-break zones which are associated with flexure or erosion have been identified： flexural slope-break zone is controlled by a persistent paleo-uplift and controls the layer-by-layer “unidirectional onlapping” of the strata above the sequence boundary towards the higher part of the slope； while erosional slope-break zone is controlled by the erosional remnant of plaeo-mounds. It is typically characterized by “two-way onlapping” towards the residual mounds or filling along the lower part of the valleys. The two types of slope-break zones both control changes in stratigraphy and sedimentation， and are conducive to the formation of lithostratigraphic traps of up-dip onlapping， lowstand filling and truncated types. The research results are of great significance to guide the exploration of large-scale lithostratigraphic plays under the control of paleotopography.

Based on the analysis of core， thin section， well logging data and seismic data and the study of rock types， sedimentary microfacies and sequence stratigraphy， the rock types and sedimentary microfacies， sedimentary system， sedimentary facies and their evolution model of the Upper Cretaceous Mishrif Formation in the northeast of the Rubal Khali Basin， west of the United Arab Emirates in the Arabian plate have been established. From the study of rock types， sedimentary microfacies， it finds that Mishrif Formation mainly develops reef limestone， grainstone and packstone， distributing in four typical microfacies， namely reef-shoal complex， grain shoal inter-shoal channel/sag and fore-shoal（middle ramp）， with high contents of rudist or bioclastic， strong energy of water， and good reservoir property characteristics. Combined with the seismic profile， it is recognized that Mishrif Formation developed rimmed platform controlled by fault activity and overall regressive background in the early and middle stages. In the late stage， Mishrif Formation developed ramp deposits due to the stable structure background. Furthermore， the isolated platform deposits developed in the northeast of the study area in the early stage. In the middle and lower members of Mishrif Formation， grain shoals and reef-shoal complex are widely developed in the open platform and platform margin， and gradually move eastward； the upper member is affected by transgression， and the water body is deepened， and the study area mainly develops small grain shoals under the background of shallow gentle slope.

The shale of marine-continental translational facies is characterized by thin bedded layers， various lithology and multiple interstratifications. Aiming at the high-resolution sequences correlations of these shales， we establish a stratigraphic delineation method combining high-resolution stratigraphic sequence and cyclic stratigraphy. Using the data from logging curve-assisted rock cores and field section， the INPEFA curve obtained from the processing of logging curve and the time-frequency features extracted by wavelet transform， the high-resolution stratigraphic interface identification and multi-well isochronous comparison of the transitional shale in the 2^nd Member of the Shanxi Formation were obtained. Compared with the conventional natural GR， the medium and short-term cycles points of the GR-INPEFA curve can significantly improve the identification accuracy of sequences interfaces. Wavelet coefficient curves and time-frequency mapping analysis with different scale factors can achieve the identification and comparison of medium-term and short-term cycle interfaces. Integrated INPEFA and wavelet transform technology， the 2^nd Member of the Shanxi Formation is divided into three mid-term cycles （from bottom to top： MSC1， MSC2 and MSC3） and 12 short-term cycles （from bottom to top： SSC1-SSC12）. The three medium-term cycles correspond to Sha₂¹， Shan₂² and Shan₂³ sub-members respectively. The short-term cycle are well coupled with the evolution of higher-order sequences and strata development. Finally， the coupling relationship of high-resolution sequence， mineral composition associated with reservoir characteristics is analyzed. It showed that SSC1 in lowest part of MSC1 is prone of excellent shale reservoirs. The medium-term and short-term cycles held significant implications for further stratigraphic correlations and exploration activities. The technic integration of multi-scale based logging cycles shows advantages for stratigraphic framework construction in a lithologically-complex shale interval.

Great breakthroughs have been made in oil and natural gas exploration in Wusonger Formation of the Lower Cambrian in Tarim Basin， NW China， but there is almost no research on the sedimentary background conditions. The sedimentary paleogeographic pattern， sedimentary environment and distribution of reservoir were systematically analyzed based on outcropping data in Aksu area， logging cuttings， C/O isotopic curves， well logs and seismic data. The results indicated that：（1）The sedimentary sequence and stratigraphic distribution of the Wusonger Formation in Tarim Basin were controlled by paleo-uplift and marginal sags. The Wusonger Formation in the paleo-uplift region was over-layed with thin thickness， including mixed carbonate-siliciclastic tidal flat and weakly rimmed platform facies. The strata in the marginal sag are complete and thick， and the deep-water basin facies and confined lagoon facies are developed. （2） The sedimentary sequence of the Wusonger Formation is generally characterized by a complete “transgression and regression” sedimentary cycle. The Wusonger Formation depositional stage platform margin was recognized from Lunnan area to Gucheng area， which jointly controls the development of carbonate-siliciclastic tidal flat and weakly rimmed platform during the sedimentary period. It is the first set platform margin of the Cambrian in Tarim Basin. （3） The Wusongger Formation has types of dolomite reservoirs， platform margin mound-shoals， reef back shoal and thin-layer platform inner shoals in the intertidal zone， with large area distribution. The first two types， mainly developed in the Lunnan-Gucheng areas， are of high quality and up to 12 070 km². Together with the upper Mid-Cambrian gypsum-salt rock， they form the first set of effective assemblage of the Cambrian pre-salt realm. As Well Luntan1 has obtained industrial oil-gas flow in 2020， this assemblage is considered to be favorable regions for ultra-deep oil and gas exploration.

A set of organic-rich shale-dominated source rocks series with sandy deposits was developed during the heyday of lake basin development in the 7^th Member of the Triassic Yanchang Formation （Chang 7 Member） in Ordos Basin. Over the years， aiming at the geological characteristics and exploration and development potential of this hydrocarbon source rock series， a number of theoretical studies and technical breakthroughs have been carried out. The research results show that： Shale oil in Chang 7 Member is mainly divided into two types： Interlayer and shale. The interlayer type can be further subdivided into gravity flow interlayer oil and delta front interlayer shale oil， and the shale type can be further subdivided into laminar shale oil and foliation shale oil. Gravity flow interlayer shale oil is highly charged by high quality source rocks in the middle of the lake basin. The sandy reservoir has high felsic content， good fracturing ability， numerous micron-size pores and good connectivity. Scale economy development has been realized in the Qingcheng Oilfield which was proved in the gravity flow interlayer shale oil. The thick sandstone reservoirs of delta front interlayer shale oil have good lateral continuity， lateral migration and accumulation of oil and gas， and large porosity of sandy reservoirs. Breakthroughs have been made in horizontal well tests， and it is a realistic backup field. The single sand body of laminar shale oil has thin thickness and high muddy content， which leads to low penetration rate of high-quality reservoirs， but high degree of oil and gas charging. The determination of “sweet spot” evaluation standard and the breakthrough of development technology are the next direction to be explored， and there is a huge amount of prospective resources. The foliation shale oil has high content of mud-scale felsic minerals， which is conducive to fracturing， reservoir space is small with porosity less than 2% and structure is complex， but hydrocarbon recovery and prediction resources are huge. At present， the risk exploration and in-situ conversion process of pure shale reservoirs are progressing steadily.

A set of fine-grained sediments of organic-rich shale interbedded with thin layer silt and fine grained sandstones developed in the Chang 7₃ sub-member of the Ordos Basin. It has the characteristics of overall hydrocarbon generation and general oil-bearing. It is of great significance to clarify the hydrocarbon content， occurrence state and hydrocarbon components of different types of fine-grained sediments for the potential analysis and sweet spot selection of this type of shale oil resources. This study is based on the systemical core testing and analysis of the Chang 7₃ sub-member of Well CY1， movable hydrocarbon research on four fine-grained sedimentary rock types is carried out， including black shale， dark mudstone， siltstone and fine-grained sandstone， by using multi-granular multi-polar sequential extraction methods， and the movable hydrocarbon resources of shale oil in the Chang 7₃ sub-member is evaluated in the Ordos Basin. The research results show that the hydrocarbon content and its components of different types of fine-grained sediments under different particle size crushing conditions（1 cm³，0.5 cm³，150 mesh） are analyzed by multi-particle multi-polar sequential extraction. The unit extraction amount of hydrocarbon is fine-grained sandstone>black shale>siltstone>dark mudstone. The soluble organic matter extracted by step 1 and step 2 is mainly light-medium components and belongs to movable hydrocarbons. Soluble organic matter extracted by steps 3 and 4 is immobile hydrocarbon. Based on the above test methods， the movable hydrocarbon of black shale， dark mudstone， siltstone and fine sandstone in the Chang 7₃ sub-member are 3.35 mg/g， 1.45 mg/g， 3.28 mg/g and 4.48 mg/g， respectively. The movable hydrocarbon resources of 220 km² shale oil in Cheng 80 well block in the Chang 7₃ sub-member were evaluated. The preliminary evaluation results were （0.37-0.51）×10⁸ t. The distribution area of shale oil in the Chang 7₃ sub-member in the Ordos Basin is about 1.5×10⁴ km². Through analogy analysis， it is estimated that its movable hydrocarbon resources are （25-35）×10⁸ t. This type of shale oil is expected to become a new replacement area for oil exploration in the basin.

Rich shale oil resources are contained in the 7^th Member of the Yanchang Formation （Chang 7 Member） in the Ordos Basin. The exploration and development of the Chang 7 Member sandstone interbedded shale oil has made substantial breakthroughs. The exploration and development potential of the shale oil， an important oil and gas replacement for Changqing Oilfield in the future， is huge. But its related geological basic research is relatively weak. This paper gives elaborations and thinkings on basic science issues， including： Characteristics of mud shale， the significance of shale oil exploration， the restoration of the formation of paleo-environment， the organic matter enrichment effect of tuff and the catalysis of hydrocarbon generation， etc. It is believed that continuous attention should be paid to related geological basic research， such as pure mud shale-type shale oil， and modern lacustrine semi-deep lake-deep lake facies sedimentation investigations can provide valuable ideas and methods for the study of mud shale formation， paleoenvironment restoration and formation mechanism. Meanwhile， we should pay close attention to the research on the catalysis of tuff on the hydrocarbon generation of source rocks and carry out a series of thermal simulation experiments on the catalysis of enriched elements in the tuff， providing important basic geological parameters for the exploration and development of Chang 7 Member pure mud shale-type shale oil.

Rich shale oil resources are developed in the Chang 7 Member of the Mesozoic Triassic Yanchang Formation in northern Shaanxi area， Ordos Basin. This paper mainly uses core， thin section， well logging and other data， focusing on high-precision pore analysis techniques such as scanning electron microscopy， micro-CT， two-dimensional FIB-SEM testing， etc. to finely portray the micro-features and to discuss its main controlling factors. The pores of the Chang 7 shale oil reservoir in the study area are mainly micro-pores with a radius of 2.0-50 μm and a throat radius of 0.3-13 μm. Numerous clustered pore-throat units are formed by micro-nano-level and micro-level throat connecting micro-level pores. The porosity is distributed between 3.0% and 13.0%， and the average porosity is 7.0%. The permeability is between 0.02×10^-3 μm² and 0.30×10^-3 μm²， the average permeability is 0.15×10^-3 μm². The mercury injection curve is characterized by low displacement pressure， high mercury removal efficiency， and high proportion of thick throat. The Chang 7 Member shale oil reservoir in the study area has fine grain size and high content of plastic components. The main factors that cause its pores to decrease are the strong early compaction and the strong cementation of clay minerals and carbonates. The dissolution and the protective effect of the chlorite film have a certain pore-enhancing effect. The potential for Type I exploration and development of Chang 7 Member shale in northern Shaanxi area is huge. Compared with Qingcheng area， the class Ⅰ multi-stage superimposed sandstone reservoir of shale oil has great exploration and development potential in northern Shaanxi area.

The first Member of Maokou Formation has great potential for gas exploration，but the problem of unclear understanding of sedimentary facies always exists. Based on the fine centimeter-level description of two latest drilling cores in central Sichuan Basin and multiple field outcrop observations, combined with the analysis of laboratory data and logging curves，a detailed analysis of sedimentary facies markers is carried out, and a new sedimentary facies division plan of the first Member of Maokou Formation is proposed. The main difference between eyeball-shaped limestone and eyelid-shaped limestone lies in the amount of argillaceous content, and natural gamma curve can effectively distinguish these two lithofacies. The marine anoxic environment, a large number of storm sedimentary structures and siliceous bioclasts indicate that the first Member of Maokou Formation was deposited in a ramp carbonate platform environment and was affected by storm action and associated storm upwelling. Based on the facies markers，the first Member of Maokou Formation is divided into two subfacies：The outer belt of middle ramp and the upper part of outer ramp. The outer belt of middle ramp includes three microfacies: Storm debris flow, storm beach, storm inter beach depression. The upper part of outer ramp has relatively high content of eyelid-shaped limestone, the microfacies combination is particle flow and static mud intercalated debris flow, which generally develops in the upper part or the top of the first Member of Maokou Formation.

Microfractures at the Ziliujing lacustrine shale at Fuling area in eastern Sichuan Basin were investigated via core observation, SEM image observation and high pressure mercury injection, and the contribution of microfracture development to reservoir capacity was quantitatively discussed. The following understanding is obtained: (1) Fracture types in lacustrine shale reservoir are defined; (2) The contribution of fractures to lacustrine shale reservoir is determined. Results show that the microfractures in the Lower Jurassic Ziliujing lacustrine shale reservoirs in eastern Sichuan Basin can be divided into three types with four groups: Microfractures related to sedimentation (bedding fractures), microfractures related to diagenesis (clay?mineral shrinkage fractures) and microfractures related to hydrocarbon generation (organic?matter shrinkage fractures and organic?matter?cracking fractures). High pressure mercury injection and plane porosity determination confirm that microfractures in lacustrine shale reservoirs have good reservoir performance, whose contribution to shale reservoir capacity is about 25%.

Deep shale gas (3 500-4 500 m) is the important replacement field of shale gas production growth in China in the future. Research on the key characteristics of deep shale gas reservoirs is the key to clarify their basic geological characteristics and establish a suitable development method. In order to clarify the characteristics and controlling factors of the adsorbed gas in the deep shales of the Longmaxi Formation, comprehensive analysis tests such as high-pressure methane adsorption, low-temperature nitrogen and carbon dioxide adsorption were carried out, and adsorption model fitting and comparative analysis were conducted. The results show that the adsorption isothermal curves of deep shales also have a downward trend when the pressure is high, and the adsorption characteristics have no obvious change. This is mainly due to the lack of microscopic pore structure characteristics of deep shale and middle-deep/middle-shallow shale. The comparative analysis of three commonly used adsorption models shows that different adsorption models can well fit the adsorption curve of deep shale, but the absolute adsorption capacity after conversion shows the same law: DA-LF model > DR model > Langmuir model. Combined with the analysis of the correlation between the pore structure and the amount of adsorbed gas, it is believed that the DR model based on micropore packing is more suitable for characterizing the adsorption law of deep shale. Through correlation analysis, it is believed that TOC is the key material factor that controls the adsorption of deep shale gas, and the specific surface area of ??micropores is the key space factor. Compared with middle-deep/middle-shallow shale, deep shale has higher siliceous content, lower calcite content, lower TOC content, and lower adsorbed gas. The proportion of adsorbed gas is only about 30%.

The black shale of the Lower Cambrian Niutitang Formation in Guizhou province is a set of good source rock. Based on the summary of previous research results and the analysis of sedimentary paleoenvironment characteristics of the black shale， its lithofacies are classified， and then the distribution of lithofacies is analyzed. Moreover， the coupling relationship among the distributions of lithofacies， sedimentary environment， and organic matter content are compared. The results show that： （1） the black shale of Niutitang Formation is mainly composed of siliceous and argillaceous shales； （2） vertically， the redox environment of shale deposition changes from anoxic condition to oxic condition from bottom to top， and siliceous shale is mainly developed in anoxic environment of deep water phase， while clay-rich siliceous shale is mainly developed in suboxic environment； （3） laterally， the anoxic environment of carbonate platform facies in Well JY1 mainly develops argillaceous/siliceous mixed shale， while the suboxic environment of slope to basin facies in Well TX1 mainly develops silica-rich argillaceous and siliceous shales； （4） both of basins and carbonate platforms facies are enriched in organic matter， which is mainly enriched in siliceous shale.

Based on the outcrop and drilling data of the Sichuan Basin and its periphery， this paper reveals the concretion developmental characteristics of the Lower Cambrian Qiongzhusi Formation and its significance to the environment. Three preliminary conclusions are drawn： （1） The regional difference between the exposure layer and the lithofacies characteristics of the concretion in the Qiongzhusi Formation is large. In the eastern Sichuan， western Hubei， western Hunan， northern Guozhou and southern Sichuan Depression area， the concretion develops in the section of SQ1， and is mainly composed of calcareous siliceous mixed shale facies， siliceous shale facies， dolomitic shale facies and dolomitite facies. The clay content is generally less than 25% and is significantly less than the surrounding rock， and the TOC is generally higher in the lower concretion layers and less in the upper concretion layers. In the central Sichuan and northern Sichuan depression areas， the concretion appears in the sections of SQ1and SQ2， and is dominated by calcareous shale facies and marlstone facies. The calcic content is obviously higher than that of surrounding rock， and the clay content is less than that of surrounding rock， and the TOC is less than 1.50%. Because mineral composition difference is high， most of the GR curves of the concretions showed trough response characteristics， reflecting the central region enriched with calcium or siliceous， and the edge enriched with clay and organic matter. （2） The concretion layer generally occurs in carbonaceous shale， silty shale and siliceous shale with a TOC over 0.7%， and especially develops in carbonaceous shale and siliceous shale of SQ1， and occasionally appears in grey silty shale with a TOC over 0.2%， showing that the concretion layer is basically symbiotic with grey shale （especially with high-quality shale）. （3） The concretion is a kind of important sedimentary response of faulted depression in marine basin. According to the distribution characteristics of concretion and black shale in the Qiongzhusi Formation， the depression process of Yangtze platform can be divided into three periods including development period（SQ1）， adjustment period（SQ2） and abortion period（SQ3）. In the period of SQ1， controlled by massive rifting and upwelling in Yangtze platform， the concretion and organic rich shale widely develop in the Lower Qiongzhusi Formation. In the periods of SQ1 and SQ2， while rifting activity of Yangtze platform decreases and shrinks， and while sea level falls and upwelling recedes to the southeast， the concretion and organic rich shale just appear in the local depression area.

For a long time， the Chang 7₃ sub-member of the Ordos Basin has been studied mainly as a single source rock， and the research involving the characteristics of multiple rock types and the integration of source and reservoir is relatively weak. Based on the related analysis data of lithology and physical properties， combined with fine well logging interpretation， the characteristics of rock type in the Chang 7₃ sub-member are discussed in detail， and the characteristics of reservoir and exploration significance of different types of rocks are discussed. There are black shale， dark mudstone， fine sandstone， siltstone and tuff in the Chang 7₃ sub-member. The storage space of sandy rocks is mainly composed of feldspar dissolved pores and residual intergranular pores supported by rigid particles. The storage space of shale and mudstone are mainly composed of clay mineral intercrystalline pores， pyrite intercrystalline pores and clastic particles intergranular pores. Organic matter pores are basically not developed， but organic matter shrinkage cracks are common. The filling of pores and throats with clay minerals reduces the porosity and seepage capacity of sandy rocks. Carbonate minerals are mainly cemented， which reduces the porosity of sandy rocks. The high content of feldspar and quartz is not only conducive to the preservation of primary intergranular pores， but also conducive to the development of secondary dissolution pores of feldspar， forming a higher movable fluid saturation. There is a clear positive correlation between the reservoir properties and oil-bearing of sandy rocks in the Chang 7₃ sub-member. It is the key to improve the shale oil production of the Chang 7₃ sub-member to find sandstones with high feldspar and quartz mineral content， low carbonate cementation， and low clay mineral content. It is preliminarily estimated that the total amount of retained hydrocarbon resources in Chang 7 mud shale is about 15 billion tons， and the amount of movable hydrocarbon resources is about 6 billion tons. Black shale with high brittleness index and high oil content is preferred， and high-efficiency seepage improvers are developed. The integrated design of pressure-flooding and production， increasing fracture width， fracture height and improving the conductivity of artificial fractures are important technical means to realize the production of shale-type shale oil.

During the Cenozoic， sea-land transition processes have important controlling effect on the depositional and petroleum geological characteristics of the northern South China Sea sedimentary basins. Based on the latest research results of IODP and the existing data in the basin， researches about the formation process of marine sediments in the northern South China Sea are carried out， and its geological significance for hydrocarbon exploration is carried out， in order to provide a basis for the future exploration and development of oil and gas resources. With the seafloor expansion process， the northern South China Sea correspondingly showed a westward and southward marine transgression during the Cenozoic. In Eocene， marine transgression firstly occurred in the Taixinan Basin in the eastern South China Sea. Later it was not until Late Oligocene that marine transgression occurred in the Yinggehai Basin of the western South China Sea. IODP 367/368 site revealed that the initial marine transgression occurred at ca. 34 Ma， and coincided with the start of the South China sea seafloor spreading. The southwest sub-basin of the South China Sea was originally formed at ca. 23 Ma， and large-scale transgression with drastic sedimentary environment changes took place during this time. Marine source rock strata in the northern South China Sea basins gradually get younger from east to west， which is also consistent with the westward marine transgression processes. Under the comprehensive impacts of both South China Sea expansion and global sea level changes， carbonate platforms also evolved from east to west， and from south to north， and formed a self-generation and self-storage oil and gas reservoir pattern in the northern South China Sea. Conclusively， sea-land transition has controlled sedimentary infilling processes within different basins， which were formed as material foundation for petroleum resources. Horizontally， the northern South China Sea source-reservoir-cap assemblage was dominated by provenances and sedimentary environment evolution. Vertically， on the other hand， it was mainly controlled by regional tectonic events and sea level changes.

The Carboniferous Benxi Formation shale is an important target interval for shale gas exploration in the Upper Paleozoic in the central and eastern Ordos Basin. On the basis of its representative field profile， drilling core system observation and sampling analysis， using the analyticaldata of major and trace elements， combined with the test data of the whole rock mineral composition， organic carbon content， organic microscopic composition， and so on， the palaeoclimate， water environment and the relationship with the development of organic-rich mud shale during the sedimentary period of the First Member of Benxi Formation in the eastern Ordos Basin are studied. The results show that the shale in the First Member of Benxi Formation of the study area is mainly clayey shale and siliceous shale， and quartz and clay minerals are absolutely dominant in the mineral composition； the CIA， Sr/Cu， and C value parameters indicate that the sedimentary period of the first member is mainly hot characteristics of wet paleoclimate； Sr content， Sr/Ba， Ba/Ga and other parameters indicate that the salinity of the sedimentary water in the upper and lower sub-members of the member is saline water， saline water-brass water， respectively，indicating that the water body salt in the late depositional period of this member was at relatively high degree；V/（V+Ni），Ce_anom，Th/U and other parameters indicate that the water body in this sedimentary period was dominated by anoxic-poor oxygen environment. The hot and humid paleo-climate， the saline anoxic-poor sedimentary water environment and other good organic matter preservation conditions are favorable factors for the development of organic-rich shale in this section， especially the upper subsection. The development of high-quality shale provides a good foundation for shale gas exploration in the study area.

A mixed siliciclastic-carbonate succession is developed in Benxi Formation in the Gaoqiao area of Ordos Basin. On the basis of previous researches， sedimentary characteristics and sequence stratigraphy in a mixed silicilastic-carbonate depositional system of Benxi Formation were studied based on outcrop， core data， logging and well logs data in Gaoqiao area of Ordos Basin. It shows that the Benxi Formation is mainly composed of tidal flat depositional system which is subdivided into the siliciclastic tidal flat facies， the mixed tidal flat facies and mixed lagoon facies. According to the principle of sequence stratigraphy， one regional unconformity surface， one tectonic subsidence transition surface and one lithology and lithofacies transition surfaces are identified. The Benxi Formation is divided into SQ1-SQ2 of the 3^rd-order sequences. Each sequence is mainly composed of transgressive system tract （TST） and highstand system tract （HST）. The mixed siliciclastic-carbonate succession of Benxi Formation is developed under the circumstance of dominated silicicclastic sediments. Mixed sedimentation mainly occurred at the stage of TST of SQ2.The lithologic and lithofacies assemblages of mixed siliciclastic-carbonate succession are different in different sedimentary areas. The intertidal sandstone and mudstone are superimposed on the tidal channel facies sandstone and then to the limestone in the mixed tidal flat area. The lagoon mudstone is superimposed on the limestone in the mixed lagoon area. The limestone is superimposed on the subtidal sandstone and intertidal sandstone in the transitional area of the mixed tidal flat and the mixed lagoon.

There are many types of transitional facies shale， and the types of organic matter are complex. They are neither completely the same as continental nor completely the same as the characteristics of marine shale. Discussing transitional shale facies and their characteristics is a further understanding of shale gas storage space. This paper takes the Well M1 and Well DC1 shale of Permian Longtan Formation in the Sichuan Basin and its surrounding areas as the research objects ， combined with core observation， ordinary optical thin section observation， and argon ion polishing scanning electron microscope observation. The lithofacies are divided and compared and their characteristics are described. The results indicate that the shale lithofacies of the Longtan Formation in the typical areas of the Sichuan Basin and its periphery can be divided into five major categories according to the mineral content， which are clay shale facies， calcareous shale facies， siliceous shale facies， calcareous mixed shale facies， siliceous mixed shale facies. According to the abundance of organic matter， eight sub-categories are further divided into ultra-high organic matter siliceous shale facies， ultra-high organic matter siliceous mixed shale facies， ultra-high organic matter clay shale facies， high organic matter siliceous shale facies， high-organic clay shale facies， medium-organic calcareous shale facies， medium-organic clay shale facies and low-organic calcareous shale facies. Clay shale facies， siliceous shale facies and siliceous mixed shale lithofacies with high abundance of organic matter is favorable production zone， while calcareous and calcareous mixed shale facies with low abundance of organic matter is an unfavorable production zone. Clay shale facies is the most commonly developed lithofacies in shale facies. The abundance of organic matter in clay facies shale facies is higher than that of marine clay shale facies shale.

In recent years， shale gas exploration and development of O₃w-S₁l¹ in southern Sichuan Basin have gradually expanded to the deep reservoirs （vertical depth between 3 500 m and 4 500 m）. Preliminary progress have been made in two deep areas， including LZ block and DZ block， and the results of shale gas exploration and development are different （the former is obviously superior to the latter）， which is mainly related to the difference of enrichment conditions. This article takes Wufeng-Longmaxi formations of LZ block and DZ block as the research objects， and has comprehensively made use of the latest data of drilling， logging， well logging， seismic and experiments， and finally has clarified the characteristics， differences and main controlling factors of enrichment conditions in two blocks. The researches show that： （1）LZ block is superior to DZ block in shale gas enrichment elements， such as formation thickness， organic matter abundance， physical property characteristics， gas bearing property， as well as the thickness and quality of shale reservoir. （2）During the formation period of Wufeng-Longmaxi formations， LZ block was always located in the sedimentary center of deep-water continental shelf in southern Sichuan basin， and its paleosedimentary environment was superior to that of DZ block. And the difference of paleosedimentary environment resulted in the difference of organic matter accumulation and reservoir scale （thickness and quality） in the two blocks. （3）The preservation condition of DZ block is obviously controlled by fault-natural fracture system， while the shale gas leakage in LZ block is less affected by fault-natural fracture system. The pressure coefficient is the largest in southern Sichuan Basin， and the preservation condition is better. The comprehensive study suggests that， in the two deep areas of LZ block and DZ block in southern Sichuan Basin， the main controlling factors of shale gas enrichment difference are paleosedimentary environment and preservation conditions. The concept of "exploring deep-water shale reservoir in the deep area" should be upheld in the exploration and development of deep shale gas in southern Sichuan Basin. Several wide and slow syncline structures which developed among the fault-anticlines in the south side of southern Huayingshan fault-zones should be the potential favorable areas for shale gas exploration in the next stage. And the geological conditions of S₁l^1-1-4 in LZ block are superior， with the feasibility of three-dimensional development for double-layers.

The Neogene in the Yiliping area of Qaidam Basin is a potential area of oil and gas exploration. In order to make clear its environmental characteristics of the ancient lakes sedimentary period and discusses the controlling factors of high quality hydrocarbon source rock development， we select the core samples from two wells—Well Li3 and Well Bo1 to analyze their organic geochemistry， carbon and oxygen isotope etc. The analysis and test results suggest that δ¹³C in the N₂² of Well Li3 is between -6.4‰ and -1.7‰， with an average value of -3.2‰， and δ¹⁸O is between -11.8‰ and -6.4‰， with an average value of -9.2‰. In Well Bo1 of Man’ai Depression， the ¹³C of sedimentary carbonate rock of Shangganchaigou Formation is between -2.1 ‰ and -1.5‰， with an average value of -1.84‰， ¹⁸O is between -12.4‰ and -4.9‰， with an average value of -9.66‰. The Yiliping area is in a semi-open-open， brackish lake environment， with frequent oscillations in the lake plane， relatively low average temperature， and rapid climate change. Through the study of the relationship between sedimentary environment and source rock distribution， the relatively high quality source rock in study area mainly develops in the saline environment， which is consistent with the development characteristics of the source rock in the western Qaidam Basin. Meanwhile， the lake calm period， in which the climate is relatively warm and humid， also developed good source rocks. The salinization center of Yiliping area is an important direction of gas exploration.

In order to clarify the pore structure characteristics and main controlling factors of shale in different sedimentary facies belts of the Permian Longtan Formation （Wujiaping Formation） in the Sichuan Basin， we performed scanning electron microscopy（SEM）， mercury intrusion， nitrogen adsorption isotherm and three-dimensional focused ion beam （3D-FIB） analyses on cores in Well DYS1 of Qijiang area and the outcrop samples of the Lichuan Shaxi section， which allows us to classify the pore types， numbers and structures. The results show： （1） The tidal flat lagoon phase shale of the Longtan Formation in the Well DYS1 mainly developed coal and adjacent dark mud shale. The pore types are mainly parallel plate， splint micro cracks and clay mineral pores. The organic structure pores are relatively undeveloped， the pore size is less than 50nm， the distribution is multimodal， and the pore connectivity is medium. （2） The Wujiaping Formation of the Lichuan Shaxi section in the deep-water shed is dominated by dark shale， and the pore type is mainly composed of ink-like asphaltic organic pores. The pore size is less than 50 nm， the distribution is unimodal， and the pore connectivity is relatively good. （3） It is clear that the organic matter type， TOC content and mineral composition are the main controlling factors affecting the pore development of Longtan Formation and Wujiaping Formation. The deep shale developed kerogen type II1， the TOC and siliceous mineral content have a good positive correlation with the pore volume， and the organic pores are more developed. The tidal flat-lagoon phase coal and shale develop type III kerogen， clay mineral content and TOC are positively coupled， and positively correlated with pore volume， but clay minerals have greater influence， and organic matter pores have a smaller proportion.

Fluvial facies is a significant type of hydrocarbon reservoirs in Mesozoic and Cenozoic continental basins in China, while the strata division of fluvial facies has always been a difficult theme. In Chuanzhong-Chuanxi area of Sichuan Basin, Shaximiao Formation developed fluvial facies. Based on the theory of continental high resolution sequence stratigraphy, combined with the principle of point-line-plane, this paper attempted to carry out sequence stratigraphy research on Shaximiao Formation. The results showed that: (1) Shaximiao Formation can be divided into three third-order base-level cycles and five fourth-order base-level cycles. The five fourth-order base-level cycles respectively corresponded to the first member, section 1 in second member, section 2 in second member, section 3 in second member, section 4 in second member of the Shaximiao Formation. (2)The base-level cycle affected the development and superimposed pattern of the source channel. When the base-level was high, the accommodation space was large, the strata got deposited quickly, and the channel was relatively spatial independent with small scale, the mudstone content was large. Differently, when the base-level was low, the strata got deposited slowly, the channel migrated frequently and incised each other, resulting in the formation of large scale channel, and the content of mudstone was relatively low. The sequence stratigraphic classification of Shaximiao Formation not only provided a high resolution isochronous stratigraphic framework, but also has a function of reservoir prediction, which is of great significance for gas exploration and development of the Shaximiao Formation.

A breakthrough in Wufeng-Longmaxi shale gas exploration has been made in Dingshan tectonic area in the southeastern margin of Sichuan Basin, however, compared with the Jiaoshiba structure in Fuling shale gas field, its enrichment and high yield factors reflect its own particularity. Therefore, this paper takes Dingshan and Jiaoshiba Wufeng-Longmaxi formations in Sichuan Basin as the research object. Through the comprehensive use of drilling, logging, seismic and laboratory data, the differences of the main enrichment conditions in the two regions are identified, and two types of shale gas accumulation and enrichment models are established. The results show that: (1) For the Dingshan high-quality shale, the layer with TOC≥3% is only developed in the ①-③ layers of the first segment of Wufeng-Longmaxi formations, with a thickness of 15-19 m, which is significantly thinner than that of Jiaoshiba area (nearly 38 m of Well JY1); (2) The preservation conditions of the Dingshan structure are obviously controlled by the Qiyueshan fault, and the pressure coefficient, porosity and gas content of the shale gas layer increase significantly in the area far away from the Qiyueshan fault, deeper buried slope zone and in the deep buried gentle zone. However, the preservation condition of Jiaoshiba structure is obviously affected by the fault of the surrounding control structure, and the pressure coefficient, porosity and gas content are only significantly reduced near the fault; (3) There is no significant difference in brittleness between the high quality shale segment in Dingshan and that in Jiaoshiba. However, due to the large change of burial depth in Dingshan area, the in-situ stress and rock fracture pressure of the high quality shale segment with burial depth of 3 500-4 500 m increase obviously. The study shows that the sedimentary environment has caused some differences in the primary shale quality between the two regions. Dingshan area is “relatively rapid regressive” continental shelf facies, and Jiaoshiba area belongs to “slow regression type” continental shelf facies. The fault, which controls the structure characteristics, is the main factor that causes the different way and degree of shale gas escape. According to the above characteristics, the “nosed fault-anticline enrichment” accumulation model in basin margin of “Qiyueshan fault zone main body control, shallow burial zone vertical and horizontal joint escape, enrichment in deep buried areas” is established in the Dingshan area, and the accumulation model of “fault-anticline enrichment” in Jiaoshiba area of internal Sichuan basin is characterized by “vertical dispersion of the control edge fault is dominant, the transverse dispersion is weak and the main stable region is enriched”.

The Yichang slope, located in western Hubei Province, is a new area for shale gas exploration of the Cambrian strata outside the Sichuan Basin. Few studies have focused on the shale gas enrichment characteristics of the Yichang slope, which developed on the ancient Huangling anticline. Based on the analysis of sedimentary, structural and the latest seismic and drilling data, as well as laboratory test, the sedimentary, tectonic and hydrocarbon accumulation characteristics are analyzed. Compared to other region of the Middle Yangtze, it is conformed that the study area has experienced three important key tectonic stages, namely the embryonic uplift in the Indosinian Period, the rapid uplift and denudation in the Yanshan Period, and the filling and reconstruction in the Himalayan Period, respectively. The relatively stable tectonic conditions in Yichang area have important influences on shale gas accumulation: (1) At the end of the Tongwan tectonic movement, the paleogeographic pattern of early Cambrian had a direct influence on the distribution of organic shale in Yichang area, and played an important role in controlling the formation and distribution of shale gas. A positive correlation between gas content and TOC content indicate that the abundance of organic matter is the key factor influencing shale gas enrichment. (2) The Huangling anticline, which began to rise in the Indosinian tectonic movement and rose rapidly in the Yanshan movement, controlled the structural subsidence of the Yichang area. The Lower Paleozoic shale strata is characterized by suitable burial depth, earlier tectonic uplifting than the west Hubei area. This relatively lower thermal maturity of the organic matters in the Sinian-Early Paleozoic shale is particularly special among the high maturity background in the south China. Organic nanopores formed an important shale gas storage space. (3) This ancient anticline played an important role in protecting the Yichang slope from suffering structural alteration and destruction during the multi-stage strong tectonic activities of the Mesozoic and Cenozoic in the South China. Tectonic activities are characterized by structural uplift with limited fracture activity and weaker tectonic deformation. Although significant uplift and erosion of overburden rocks occurred in the Late Indosinian orogeny, the Yichang area was not significantly influenced during the tectonic movement comparing to the surrounding area. The Shuijingtuo shale in Yichang area is characterized by suitable structure preservation and low permeability. Shale gas is preserved effectively in this monoclinal structure and becomes the main exploration target in this area. (4) Bedding slip joint related to stratum slip shear joint during thrusting was an important reservoir space for shale gas. Shale gas exploration of the Yichang area confirmed that the paleo-uplift, the periphery of the paleo-tectonic slope, and the fault footwall of the thrust nappe structure are favorable exploration areas for shale gas.

Lower Cambrian Xiaoerblak Formation is an important exploration target of Cambrian pre-salt in Tarim Basin, but the limited knowledge of sedimentary facies and reservoir genesis led to the restriction of exploration. This study took Xiaoerblak outcrop of Keping area as an example. Based on detailed description, 110 thin sections identification and multi-parameters geochemical (order degree, trace elements, rare earth elements, δ¹³C, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr, U-Pb dating and cluster isotopes) data analysis, it was found that Xiaoerblak Formation can be divided into three members, and microbial dolomite is the main lithology. The characteristics of lithofacies assemblage form bottom to up indicate that it can be described as a complete three-order sequence. The sedimentary environment of Early Cambrian Xiaoerblak Period in Keping area characterized by warm-dry climate, normal-higher sea salinity, gradually increase oxygen content and upward shallower water. The sedimentary sequence was microbial layer-microbial mound/shoal-tidal flat in carbonated ramp background. Dolomitization took place in penecontemporaneous-early diagenetic stage and the main dolomitization fluid was high-saline seawater. Primary microbial framework pores and vugs which formed by the dissolution atmospheric water are the main reservoir spaces. Reservoir was mainly controlled by sedimentary microfacies, high frequency sequence interface and early dolomitization. These research results are of great significance for sedimentary facies mapping and reservoir prediction in Cambrian pre-salt field.

The Mianzhu-Changning rift trough has great potential for the development of the Lower Cambrian source rock. Total organic carbon (TOC), mineral composition, major and trace elements of the Lower Cambrian shales in the central part of the rift trough were measured to reveal the relationship between the tectonic setting, terrigenous input, paleoclimate, primary productivity, redox conditions as well as the hydrothermal activity and the enrichment of organic matter during its development period. The results show that the study area is located in the passive continental margin sedimentary environment, with stable sedimentary rate, warm and humid climate alternated by intermittent climate cooling. The TOC values range from 5.96% to 23.15% with an average content of 11.64%. Nutrient elements of P, Ba, Cu and Ni reveal the high primary productivity during this period, which is due to the increased chemical weathering caused by warm and humid climate, thus importing large amounts of nutrients into the ocean. The index of redox sensitive elements and the content of pyrite indicate that the organic-rich sediments in the second and third stages are mainly developed in the bottom water environment of anaerobic sulfurization. The abnormal enrichment of trace metals may be related to the hydrothermal activity from the seabed under the stretching background in rift during the Early Cambrian, which not only provides material for the flourishing of anaerobic chemoautotrophs, but also facilitates the formation of anaerobic sulfurization environment in the bottom water and promotes the preservation of organic matter after mixing with seawater.

The first sand group of 1^st member of Cretaceous Qingshuihe Formation in SN31 well area of Junggar Basin has thick strata. The lateral and vertical variations of sand bodies restrict the process of exploration, development and rolling evaluation in this area. Based on core observation, thin section, logging and logging data, scanning electron microscopy(SEM) and other technical methods, the lithological characteristics, physical characteristics, distribution characteristics of sedimentary microfacies of the first sand group of 1^st member of Qingshuihe Formation, and main controlling factors of physical properties of reservoir have been studied. The results show that the reservoir of the first sand group in 1^st member of Qingshuihe Formation are composed of fine-grained sandstone, sandy conglomerate, coarse sandstone and medium sandstone, with low component maturity, middle structural maturity and good physical properties, which is emphatically defined as medium porosity and medium permeability reservoir. The study area developed the underwater distributary channel, river mouth bar and sheet sand deposits of braided river delta front, and the best physical properties such as sandy conglomerate, coarse sandstone and medium sandstone reservoir are mainly developed in underwater distributary channel microfacies. The physical properties of reservoir in the study area are mainly controlled by sedimentation, and diagenesis has little influence on physical properties of reservoir. The underwater distributary channel of braided river delta front is favorable microfacies for the development of high-quality reservoirs.

The composition of the Permian Lucaogou Formation in Jimsar Sag, Junggar Basin is a key block for shale oil and gas exploration. It is of great significance to carry out the study of fine mixed rock sedimentary sequences and related research. Using core, thin section, scanning electron microscope, well logging curve, XRF, XRD and other data, combined with core phase and its combination analysis, log curve least squares fitting and lithology random simulation, etc., the sequence stratigraphic framework and sedimentary microfacies identification established a microfacies model of mixed fine-grained sediments in the study area. (1) Lucaogou Formation can be divided into 5 medium-term cycles, 9 short-term cycles and 33 ultra-short-term cycles. The medium-term cycle corresponds to the segment level, and the short-term cycle is equivalent to one sand group or small layer (including multiple single sand layers), and the ultra-short-term cycle generally corresponds to a single layer. (2) The target layer of the study area is a salt lake-delta sedimentary system with complex and variable lithology. Under the joint influence of mechanical, chemical, biological and other sedimentary effects, a mixed fine-grained rock formation composed of fine-grained clastic rocks, mudstones and carbonate rocks is formed. The sedimentary microfacies types of the reservoir mainly include sand dam, prodelta mud, sand bank, mixed bank, dolomitic flat and lacustrine mud. (3) The dessert section of Lucaogou Formation in Jimsar Sag is mainly distributed in the Upper p2l22 and p2l12 .The sedimentary model of terrigenous clastic-carbonate mixed fine-grained rocks in Lucaogou Formation is put forward. When the datum surface rises, the sedimentary environment changes from the delta outer leading sand dam and the shallow lake sand bank sediment to the shallow lake-semi-deep lake mixed bank and dolomitic flat sediment, and a large area of black gray mudstone is deposited as the datum surface continues to rise to the maximum accommodating space; When the datum is declining, the shallow lake-semi-deep lake mixed bank and dolomitic flat sediment are mainly developed. As the datum continues to decline, shallow lake subfacies sand bank and delta front sand dam deposits are developed.

In 2019, the annual output of Wufeng-Longmaxi formations shale gas in South China reached 154×10⁸ m³, making China the largest shale gas production region outside North America. Based on data of about 1 000 Wufeng-Longmaxi formations shale samples collected from typical cores and outcrops of Weiyuan, Changning, Fuling and Wuxi areas in South China, characteristics of differential enrichment of shale gas were analyzed, and its controlling factors were discussed. It is concluded that enrichments of Wufeng-Longmaxi formations shale gas in South China show differential vertically and laterally, respectively. In vertical orientation, the sweet-spot intervals of shale gas developed concentratedly, and the thicknesses, gas and TOC contents varied largely in different regions, of which in Changning and Fuling are high quality. For these four areas of shale gas exploration or development, gas contents are well correlated with TOC contents, suggesting that organic matter abundance is one of key factors controlling the enrichment of shale gas. When the Wufeng-Longmaxi formations shale deposited, the ocean surface had high productivity in general, providing prerequisites for formation of abundant organic matter. However, in the relatively stable tectonic zone, euxinic bottom water condition is the key factor controlling the formation of the sweet-spot interval of shale gas vertically and the distribution of sweet-spot area laterally, that is the key factor for differential enrichment of Wufeng-Longmaxi formations shale gas.