The Ordovician Wulalike Formation in the northwestern margin of the Ordos Basin is a key area for exploration and evaluation of marine shale gas in northern China. In this paper， through the multi-method identification and quantitative evaluation of fractures and pores in multiple evaluation wells in the northwestern margin of the basin， the development characteristics， distribution rules and main controlling factors of fractures in the lower section of the Wulalike Formation were explored and revealed. Three preliminary conclusions were obtained： （1） Open bedding fractures are generally developed in the lower section of the Wulalike Formation at the northwest margin of the basin. Single fractures are either intermittent or continuous in steps. The width of the fractures is generally 0.1-0.2 mm， and the spacing of the fractures is generally 0.5-14.0 cm. The fracture development section is characterized by double or multiple peaks in the nuclear magnetic resonance standard T₂ spectrum， and generally has the double track feature of positive amplitude difference on the deep and shallow resistivity logging curves. （2） The fracture section length and fracture porosity vary greatly. In the Majiatan-Gufengzhuang area in the southern exploration area， the fracture development degree is generally decreasing from west to east. In the Shanghaimiao area in the central exploration area， fractures are extremely developed， the continuous thickness of fracture section is generally more than 20 m， and the average value of fracture porosity is more than 1.3%. In the Tiekesumao area of the northern exploration area， the fracture development degree is generally worse than that of the central and southern areas， and also shows a weakening trend from west to east. （3） The highly brittle shale section rich in calcareous and siliceous is matched with the thrust fold and detachment since the Yanshanian period， which is the key controlling factor for the formation of fracture pores in the Wulalike Formation. Affected by the structural style and activity characteristics of different blocks， the development degree of fractures in different exploration areas is significantly different.

Ordos Basin is the second largest sedimentary basin in China with abundant oil and gas resources. After more than 50 years of exploration practice， PetroChina Changqing Oilfield Company has innovated reservoir-forming geological theories such as large delta of inland depression lake basin， continental tight sandstone gas and Ordovician karst paleo-landform. In 2022， the oil and gas equivalent has exceeded 65 million tons， and the China's largest oil and gas production base and largest natural gas production area have been built. In recent years， in order to further consolidate the resource base for continuous and stable production of oil and gas， Changqing Oilfield Company has continuously deepened comprehensive geological research， strengthened technical research， and increased risk exploration efforts in new areas. Oil and gas exploration has achieved fruitful results. Through innovative theoretical understanding of the formation of the Mesozoic Chang 7₃ laminated shale oil and the new series Chang 8₂ beach bar tight oil reservoir， the new oil reserves increased by 400 million tons； Natural gas exploration has innovated the theory of oil and gas accumulation in Ordovician undersalt， Taiyuan Formation biolimestones and Ulalik shale in the western margin of the basin， increased the scale of reserves by more than 400 billion cubic meters. At the same time， a series of new unconventional oil and gas exploration technologies such as geophysics and fracturing have been formed， and major discoveries have been made in oil and gas exploration. It is estimated that the new oil resource potential of the basin is 2-4 billion tons， and the natural gas resource potential is 2-3 trillion cubic meters. It has laid a solid resource foundation for ensuring long-term stable production of more than 60 million tons of Changqing Oilfield Company.

Middle Jurassic Lianggaoshan Formation in Fuxing area is regarded as one of the important fields of shale oil and gas exploration in Sichuan Basin. Source rock potential and reservoir quality of Lianggaoshan Formation were analyzed via integrated analysis of organic geochemistry property and pore types and pore microstructure， and thereby favorable intervals for shale oil exploration were defined. Finally， shale oil exploration potential of Lianggaoshan Formation in Fuxing area is discussed. Results show that， shallow lake to semi-deep lake organic rich shale was developed at the Lianggaoshan Formation in the Fuxing area， which is characterized by fair-good source rocks with medium organic matter abundance， good organic matter type， moderate thermal maturity and high hydrocarbon generation potential. Shale reservoirs at No.④ layer have medium storage capacity， but good oil and gas property and good movable potential. It is a favorable shale oil exploration target. The Lianggaoshan semi-deep lacustrine shale at Bashansi Syncline in Fuxing area has a solid foundation for in-situ condensate or light oil enrichment with good shale oil exploration prospects.

A set of tight limestone reservoirs has been developed in the Permian Taiyuan Formation of the Ordos Basin. In recent years， the risk exploration has made a substantial breakthrough and has become a key field of natural gas exploration. Through field outcrop， core observation， thin section identification， scanning electron microscope and stable carbon and oxygen isotope analysis and testing， petrology， reservoir space， reservoir physical properties and microscopic characteristics were studied， and the development characteristics of tight limestone reservoirs and controlling factors of favorable reservoirs were systematically analyzed. The research shows that the rock types that can be used as good reservoirs are bioclastic micrite limestone， bioclastic micrite limestone， algal boundstone， and the reservoir space is mainly dissolved pores， residual organism cavity pores， inter-crystalline pores and micro fractures. The average porosity of the reservoir is 2.1%， and the average permeability is 0.22×10^-3 μm²， belonging to low porosity and low permeability reservoirs. The formation of favorable reservoirs of Taiyuan Formation limestone in the study area is controlled by many factors， among which favorable sedimentary microfacies of bioclastic beach and biodome are the material basis for the formation of reservoirs， which determine the type of reservoir space and large plane distribution； Quasisyngenetic karstification under the control of high frequency cycle is favorable for the formation of dissolution holes， effectively improving the reservoir performance， and creating conditions for the development of thick limestone reservoirs； Fractures play an important role in improving the permeability of tight limestone reservoirs. The research results point out the direction for the next step of limestone exploration of Taiyuan Formation in Ordos Basin， and also have important reference significance for the research and exploration of bioclastic limestone reservoirs in North China platform.

The Lower Cambrian Longwangmiao dolomite is a crucial deep carbonate reservoir with great hydrocarbon potential in the Sichuan Basin， and most existing studies have focused on the central Sichuan area， while research on the dolomite of the Longwangmiao Formation in the eastern Sichuan area is relatively weak. Therefore， three field sections （Xishui Tuhe， Pengshui Banzhigou and Wuxi Xujiaba） in east Sichuan were selected for the study， and the characteristics of dolomitizing fluids and dolomite genesis mechanisms of the Cambrian Longwangmiao Formation in eastern Sichuan Basin were investigated by conducting lithological and rare earth element characteristics studies. The result shows that： （1） Three main types of dolomite developed in the study area are micrite dolomite， silty dolomite and fine-crystalline dolomite. The rare earth elements are low in various dolomites and the total rare earth content decreases as the crystal size increases， while the （Nd/Yb） SN values increase， indicating a gradual increase in dolomitization degree. （2） The gradual decrease in Ce/Ce* values and the increase in U content from micrite dolomite to fine-crystalline dolomite indicate a decreasingly oxidative environment of dolomite formation and a more closed diagenetic system. （3） The similar seawater-normalized REE partition pattern of the investigated dolomites to that of the micrites， showing positive Ce anomalies and right dip， and no significant positive Eu anomalies. These characteristics suggest that the dolomitizing fluids are likely related to seawater uninfluenced by hydrothermal fluids. （4） In summary， the micrite dolomite and the silty dolomite of the Longwangmiao Formation in the east Sichuan area were formed by evaporative concentration dolomitization during the syngenetic-penecontemporaneous phase and seepage-reflux dolomitization during the shallow burial phase， respectively， and the fine-crystal dolomite was formed by secondary enlargement of the precursor dolomite during the middle-deep burial phase. （5） In addition， combined with the sedimentary background and physical characteristics， the silty dolomite is considered to be the most important reservoir rock type of the Longwangmiao Formation in the east Sichuan area， and the early seepage-reflux dolomitization within restricted platform is most favourable to reservoir development.

The exploration and development of volcanic rocks have entered a new stage since YS1 and YT1 wells in Southwest Sichuan have made significant breakthroughs and progress in porous pyroclastic reservoirs. Based on the latest data collected by gravity， magnetic and electric seismic， drilling and field， combined with the respective advantages of geophysical and geological cognitive tools， the characteristics of basement faults and the distribution of volcanic rocks in the western Sichuan-Shunan regions were analyzed， and the relationship between basement faults and volcanic rocks was discussed. The study shows that two groups of basement faults are developed in the western Sichuan-Shunan regions， mainly in the NE direction and supplemented by the NW direction. It is believed that the NE direction faults are formed first and the NW direction is formed later， and the two groups of faults become a cross-intersectional fault system in the Jinyang-Santai and Shunan regions. The thickness of volcanic rocks in the study area is concentrated in the southwestern part of the basin and thinned toward the basin， and the thickness of volcanic clastic rocks is concentrated in the Xinjin-Jenyang area and thinned toward the surrounding area， while thin layers of volcanic clastic rocks are also developed in southern Sichuan； the distribution and development characteristics of volcanic rocks in the region are controlled by the NE-oriented deep faults that break through to the Permian， and the eruption patterns are different due to the different degrees of intersection of fractures， and the areas with high degrees of intersection of fractures have point-like and small craters that are easy to form multi-point compound central eruption patterns along the fractures and develop eruptive phase volcanic clastic rocks.

Aiming at the thin interbeds of gravity flow sandstone in organic-rich shale layer of the 7th member of Triassic Yanchang Formation （Chang7 Member） in Ordos Basin， PetroChina Changqing Oilfield Company realized the cost-effective development of interbedded shale oil in continental low-pressure freshwater lacustrine basin， discovered and proved the 1 billion ton Qingcheng shale oil field， and presented proven reserves of 10.52×10⁸ t. It took the lead in building China's first one million ton shale oil integrated development zone. With the continuous expansion of production and construction scale， the difference of geological body is obvious， and the problems of low initial production and rapid decline of single well， low recovery efficiency and high development cost become more and more prominent. Through many years of field practice， the key problems in shale oil development are put forward， and reasonable suggestions are put forward according to systematic analysis. The drilling rate of shale oil horizontal wells can be divided into longitudinal drilling rate and transverse drilling rate. Improving the longitudinal drilling rate and transverse drilling rate of high-quality reservoir is an important measure to increase the production of a single well. When deploying horizontal wells， priority can be given to the extension direction of high-quality reservoirs to improve the drilling rate of high-quality reservoirs. The contribution ratio of elastic energy of fracturing fluid to recovery is relatively low， so the reservoir reconstruction should not overemphasize large sand volume， large fluid volume， and large displacement， but should fully consider well spacing， longitudinal interlayer distribution， and fracture development， and optimize fracturing scale， construction displacement and other parameters. The change of source rock quality and the strength of diagenesis are the main reasons for the difference of oil content in sand bodies， which affect the selection of favorable areas and the distribution of high-quality reservoirs. Pre-CO₂ volumetric fracturing has obvious energy increase effect， which is an effective means to reduce viscosity and improve oil recovery. It is an important measure to ensure the efficient development of shale oil in Changqing Oilfield Company by deepening the comprehensive geological research， clarifying the main controlling factors of differential shale oil accumulation， elaborating the three-dimensional sweet spot distribution， and exploring more effective development methods.

The Lower Carboniferous Luzhai Formation in the Guizhong Depression of Dian-Qian-Gui Basin is thicker than the Longmaxi Formation in the Sichuan Basin， and is expected to become a major breakthrough field after the Sichuan Basin and Yunnan-Guizhou region. However， the geological conditions are more complicated. In order to explore the enrichment conditions and main controlling factors of shale gas in Guangxi， the Lower Carboniferous Luzhai Formation in the Guizhong Depression is taken as the research object. Using the data of drilling， logging， seismic， magnetotelluric sounding， analysis and testing， the enrichment conditions and main controlling factors are studied. The research shows that： （1） The organic-rich shale of the Lower Carboniferous Luzhai Formation in the Guizhong Depression has large thickness， wide distribution， high abundance of organic matter， good type of organic matter， high maturity-over-maturity stage， and good reservoir conditions such as high porosity. The maximum analytical gas content in the field is 2.9 m³/t， and the isothermal adsorption experiment shows that the maximum adsorption capacity is 5.32 m³/t， indicating good preservation conditions. Compared with typical shale gas reservoirs at home and abroad， Luzhai Formation has good shale gas enrichment conditions. （2） The main controlling factors of shale gas enrichment in Luzhai Formation of Lower Carboniferous Series in Guizhong Depression are： The basin or deepwater shelf facies are favorable zones for shale gas enrichment， and the combined gas of “residual hydrocarbon” and kerogen at moderate burial depth ensures sufficient gas source， with R_O of 1.5%-3.5%， which is the best window for the coupling of source and reservoir. Slow uplift and favorable structural styles are the key factors for shale gas enrichment. （3） Based on the characteristics of large denudation thickness， high thermal evolution degree and multi-stage fault activity in Guizhong Depression， it is concluded that Liucheng North area， Luzhai area， Nandan area and Huanjiang area are favorable areas for shale gas exploration in Luzhai Formation.

The main source rock of the Lishu Fault Depression in the Songliao Basin has not yet been identified. In order to reveal the Cretaceous hydrocarbon accumulation law of the southeast slope of the Lishu Fault Depression in the Songliao Basin， this paper conducted the source rock evaluation and the comparison of oil and gas sources in the shale samples of the Shahezi Formation and Yingcheng Formation of the southeast slope area of the Lishu Fault Depression， and then recovers the hydrocarbon history of the source rock. The result shows that the source rocks of the Cretaceous Shahezi Formation and Yingcheng Formation of the Lishu Fault Depression have relatively good organic carbon content and hydrocarbon production potential， belonging to medium-good source rocks. The identification of kerogen components and biomarker shows that the chalky source rocks of the southeast slope belongs to kerogen type II-Ⅲ， which is a mixed source of aquatic organisms and terrestrial higher plants and forms in a reducing environment， with a medium degree of thermal evolution， and the source rocks still in the oil-producing stage. The results of oil source comparison show that the oil and gas in the southeast slope area are all derived from the source rocks of the Shahezi Formation. The results of the reconstruction of the history of hydrocarbon production show that the source rocks of Shahezi Formation and Yingcheng Formation reached the hydrocarbon production threshold at 97 Ma and 94 Ma， respectively， and entered the peak of hydrocarbon production at 92 Ma and 89 Ma. After 66 Ma， Lishu Fault Depression was raised as a whole， and the ground temperature gradient decreased， and the hydrocarbon production effect is weakened. Geochemical analysis combined with hydrocarbon history reconstruction technology can be well used to determine the characteristics of the main source rocks in the multi-spin superposition basin， and it plays an important role in clarifying the distribution law of oil and gas reservoirs.

In order to discuss the geological characteristics of deep Longmaxi Formation shale reservoir in Zhaotong Shale Gas Demonstration area in the southwest margin of the Upper Yangtze River， taking Leibo area as an example， on the basis of field geological survey and indoor experimental data， and through regional geological data， a systematic study was carried out on the petrological characteristics， sedimentary facies distribution， organic geochemical parameters， and reservoir space types and characteristics of Longmaxi Formation shale in the study area. The mineral components in the study area are mainly quartz and clay minerals， with an average of 36.3% and 34.85% respectively， and contain a small amount of carbonate minerals， feldspar and pyrite； TOC content is 0.12%-5.94%， with an average of 2.12%； The two areas near Zhongdu town-Nan'an town and the east of Leibo county are high TOC value areas and sedimentary centers in the study area. The sedimentary facies are mainly deep-water continental shelf， which evolved to the West into shallow water continental shelf. TI value is 36.5-82.5， mainly type Ⅱ₁ kerogen； R_O is 2.34%-2.72%， with an average of 2.48%， which is at over mature stage； The average porosity is 8.99% and the average pore diameter is 5.682 nm. The pore types are mainly organic matter pores， mineral dissolution pores and micro fractures. The pore morphology is mainly nano-sized open quadrilateral parallel plate pores and densely stacked spherical intergranular pores， with a small amount of open cylindrical pores and fracture structures. The porosity of shale shows a positive correlation with permeability. Compared with the major shale gas producing areas at home and abroad， the lower shale of Longmaxi Formation in the southwest margin of Sichuan Basin shows the characteristics of high TOC content， high organic matter abundance， high maturity， high content of brittle minerals and development of organic matter pores. According to its hydrocarbon generation capacity and exploitability， it is divided into source rock section and reservoir dominated section. The upper member of Longmaxi Formation is characterized by low TOC content， high clay mineral content and developed microcracks. It is a non-source rock and a cap dominated interval.

A set of high-quality organic-rich shale is developed in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in northern Guizhou， which is expected to have a good resource prospect. However， shale reservoir characteristics， gas-bearing characteristics and their controlling factors of shale gas are still not clear. Based on the previous data and the latest drilling， this paper systematically analyzed organic matter characteristics， reservoir physical property and gas-bearing characteristics of the Wufeng-Longmaxi shales， and further discussed the factors of shale gas content. The results show that Wufeng-Longmaxi formations in northern Guizhou are shallow-deep water shelf facies， and high-quality shales are primarily distributed in the deep-water shelf facies in Daozhen-Xishui areas， with the maximum thickness of 80-100 m. Organic-rich shales in Wufeng Formation and the lower member of Longmaxi Formation have high TOC content， mostly higher than 2%， with good organic matter type and moderated maturity， and therefore they have good conditions for shale gas formation. High-quality shales have high content of brittle minerals， and therefore they are easy to be fractured. Shale pore types are various， dominated with organic matter nano-scale pores， and the studied shales have relatively low porosity and permeability. Methane adsorption capacity of the studied shales is strong， which is mainly controlled by TOC and thermal maturity. Shale gas content in different regions varies greatly. The shale gas content is relatively high in Xishui and Daozhen areas， whereas it is relatively low in Tongzi-Zhengan areas. Gas contents of the shales in the same structural unit is controlled by TOC content， nanometer-sized pore development degree and water saturation， however， shale gas content in different structural unit is determined by structural preservation condition. Shales with good preservation conditions， e.g.， wide and gentle structures， far from large faults and deep burial depth， generally have high gas content.

In recent years， dozens of tight sandstone gas exploration wells in the southeast of Ordos Basin has tapped industrial gas flows and a pilot area has been developed efficiently， showing this area has a bright exploration and development prospect for tight sandstone gas. It is well-known that good gas source conditions provided by high-quality source rocks， strong hydrocarbon generation pressurization and dynamic conditions for reservoir formation are the fundamental conditions controlling the formation of large tight sandstone gas field， but source rocks in the study area haven’t been investigated systematically. In this work， based on large amount of well logging， mud logging， core， analysis and assay data， geochemical characteristics and planar distribution of coal measure source rocks in southeast of Ordos Basin have been analyzed in detail， logging interpretation model of the total organic carbon content （TOC） of coal measure source rocks have been established， and hydrocarbon generation intensity of the source rocks have been calculated on this basis. The results show that： （1）In the Upper Paleozoic of southeastern Ordos Basin， coal， carbonaceous mudstone and dark mudstone have average TOC contents of 56.2%， 9.6% and 2.4%， respectively.The organic matter type of coal is type Ⅲ， and are all in over-mature dry gas generation stage. （2）On the plane，coal and dark mudstone are widely developed in Benxi Formation and Shanxi Formation and thicken gradually from the northwest to east， while carbonaceous mudstone is thin in the study area. （3）Logging parameters such as GR， AC and DEN matching best with the measured data were picked out to establish TOC logging interpretation models of coal， carbonaceous mudstone and dark mudstone source rocks respectively by using multiple regression method.（4）The Upper Paleozoic source rocks in the southeast of Ordos Basin have higher hydrocarbon generation intensities of （17.6-58.3）×10⁸ m³/km²，with an average of 38.4×10⁸ m³/km²， in which the coal seams have higher hydrocarbon generation intensity than dark mudstone and carbonaceous mudstone units， and the source rocks in the east part has the highest hydrocarbon generation intensity of mainly between （29.2-58.3）×10⁸ m³/km²， on average 42.4×10⁸ m³/km².

The high-yield reservoir test of the second member of the Dengying Formation （Deng 2 Member） in the Zhongjiang-Penglai area shows great exploration potential. Due to the dual effects of sedimentation and dissolution， the reservoir heterogeneity is strong and the gas-water relationship is complex. In addition to the development of dense zones in the horizontal direction， there are also dense area barriers in the vertical direction， forming multiple independent gas reservoirs with different gas-water interfaces. In this regard， based on the seismic geological characteristics of drilled wells， this paper intends to establish the seismic identification model of Dengying reservoir and dense area， and then deeply analyze the sedimentary evolution process of paleogeomorphology in the upper sub-member of Deng 2 Member， finely characterize lithologic traps， and clarify the spatial distribution law of effective reservoirs. The study shows that the high-quality reservoir of the hilly-shoal reservior is developed in the second layer of the upper sub-member of Deng 2 Member， with a thickness of 30-110 m. Laterally， it is developed in the high landform area near the platform margin， showing a continuous distribution characteristics. The dense area develops in the low part of paleogeomorphology， and has a good coupling relationship with rift of Sinian System， which has a shielding effect on gas reservoir. The practice shows that the understanding in this paper is highly consistent with the actual drilling， which can provide technical support for the exploration of Dengying Formation gas reservoir in the northern slope.

In recent years， a great breakthrough has been made in the natural gas exploration of bauxite deposits in the Longdong area of the Ordos Basin， but there is little research on bauxite deposits of the Benxi Formation in the east of the basin. It is urgent to strengthen basic geological research. Through core observation， thin section， and other experimental methods， combined with major elements， trace elements， and rare earth elements， geochemical analysis was carried out to study the paleosalinity， paleo-redox conditions， paleoclimate， and provenance characteristics of bauxite deposits. The results show that： （1） The Benxi period of the Late Carboniferous experienced multiple transgressions and regressions. The sedimentary environment changed from a marine saline water environment to a continental freshwater environment， and then changed to a marine saline water environment at the end of the Hutian period， with alternate redox conditions. （2） Bauxite deposits are significantly affected by chemical weathering. In the early stage of the Benxi period， due to the influence of the Late Paleozoic Ice Age， the temperature dropped， and then the temperature rose due to the global warming event. （3） Iron minerals in the bottom of bauxite deposits come from the underlying carbonate rocks of Majiagou Formation， and the material of bauxite and mudstone in the middle and upper parts comes from silicate rocks and magmatic rocks， with various material sources.

Multi-layer commingled production is the main feature of gas well development in Sulige tight sandstone gas reservoirs， Ordos Basin. Whether there is interference between layers and how to characterize them are important issues for effective development of gas reservoir. The physical simulation experiment process and scheme of interlayer commingled mining with fracture communication are designed， and the development simulation experiment of different interlayer combination modes is carried out. The results show that in the process of multi-layer commingled production of tight gas and water layers， whether it is only gas layers production or gas and water layers production at the same time， there is a common phenomenon of cross flow of gas and water between layers， resulting in interlayer interference and reducing the recovery of gas reservoirs. Based on this， the concept of interlayer interference index in multi-layer commingled production in tight sandstone gas reservoirs is proposed， and the interference index model is obtained by fitting the multiple linear regression method. The interference index is related to the physical properties of the reservoir. High water saturation and great permeability ratio of water layer to gas layer （greater than the critical value 1） can result in the early occurring of interlayer interference and great interference index. Finally， based on the interference index model， a new method for productivity evaluation of gas wells in tight gas reservoirs is established. The calculation results show that the interference index curve can effectively describe the interlayer interference performance of gas wells. The productivity and production performance of gas wells calculated by the productivity evaluation method based on the interference index model are consistent with the production history， which proves the effectiveness and accuracy of the interference index model. Therefore， the interference index model can effectively predict the productivity and production performance of gas wells in Sulige tight sandstone gas reservoir. The research results have important theoretical guidance and practical significance for the efficient development of Sulige tight sandstone gas reservoir.

In order to accurately characterize the pore throat structure of tight reservoir in the Chang 8 Member of the Wuqi-Zhidan area of the Ordos Basin， based on the analyses of cast thin section， scanning electron microscopy， X-ray diffraction， high-pressure mercury injection， constant velocity mercury injection， and oil-water phase infiltration， the pore throat fractal characteristics and throat fractal characteristics of tight reservoirs in Chang 8 Member were studied by using fractal theory. The relationship between fractal characteristics and reservoir porosity， permeability， and microscopic pore throat characteristics was systematically analyzed. The results show that the lithology of the study area is dominated by lithic feldspar sandstone， with an average porosity of 8.2% and an average permeability of 0.16×10^-3 μm². The reservoirs are generally tight. The pore types of the reservoir are mainly intergranular pores and dissolution pores. According to the morphology of capillary pressure curve and high-pressure mercury injection parameters， the pore throat structure of the reservoir is divided into two types： type I and type II. The constant rate mercury intrusion experiment showed that the mercury saturation of the samples in the study area was mainly contributed by the throat. The fractal dimension of throat calculated by constant velocity mercury injection has two characteristics：Fine throat section D_T1 and coarse throat section D_T2. The full aperture fractal dimension and throat fractal dimension have good negative correlation with physical properties， mercury injection saturation and mercury removal efficiency. The throat fractal dimension has a good negative correlation with the mercury injection saturation of the throat and the radius of the mainstream throat. The more homogeneous the pore throat is， the more difficult it is for the oil phase fluid to pass through the water-bearing reservoir and the lower the relative permeability of the oil phase.

The hydrocarbon accumulation period of the Lower Paleozoic Ordovician carbonate reservoirs in the western margin of Ordos Basin is not clear. Carbonate rock samples from eight Lower Paleozoic reservoirs in five typical wells in the study area were selected for petrographic analysis of fluid inclusions， microthermometry and laser Raman spectroscopy. Combined with the burial-thermal history recovery of typical wells， the hydrocarbon accumulation periods of the Lower Paleozoic Ordovician in the western margin of Ordos Basin were determined. The results show that the fluid inclusions in the Lower Paleozoic Ordovician carbonate reservoirs in the western margin of the Ordos Basin can be divided into two stages. The first stage of inclusions is mainly composed of liquid hydrocarbon inclusions and a large number of associated aqueous inclusions. The fluorescence is yellow， mainly in the form of beads distributed in the cave-filled calcite and the early fracture-filled calcite. The peak value of the homogenization temperature of the associated aqueous inclusions is between 120 ℃ and 130 ℃. The inclusions in the second stage mainly develop gaseous hydrocarbon inclusions and their associated large amount of aqueous inclusions and a small amount of asphalt inclusions， which are distributed in the late fracture-filled calcite in bands， with no obvious fluorescence， and the peak value of the homogenization temperature of the associated brine inclusions is between 150 ℃ and 170 ℃. The Lower Paleozoic Ordovician reservoir in the study area has undergone two hydrocarbon filling processes. The first stage occurred in the late stage of Early Jurassic， which was a period of large oil and gas filling. The second stage occurred in the early and middle stage of Early Cretaceous， which was a period of large gas filling.

High-quality reservoirs developed in the Bashijiqike Formation and Baxigai Formation sandstones of the Lower Cretaceous in the Bozi-Dabei area， Kuqa Depression of Tarim Basin， in which highly yielding industrial gas flow is obtained within a burial depth of 8 200 m. The target formation has experienced multiple phases of tectonic movements， and the development of multi-genetic fractures provides the reservoir with efficient storage and seepage space. Based on the results of drilling core， field profile survey， imaging logging， and experimental analysis， the authors portray the fractures in the Lower Cretaceous dense sandstone reservoir of the Bozi-Dabei area， clarify the characteristics and controlling factors of multi-genesis and multi-period fractures， and propose an effective fracture development model under geo-stress control. The Bozi-Dabei area is subjected to a high extrusion stress environment with relatively gentle deformation， mainly developed regional tectonic fractures and fault related fractures， where deformation-related factures are less developed. The results of a combination of multi-attribute data determination techniques， including fracture filling， inter-cutting relationship， fracture filling isotope， inclusions and cathode luminescence tests， indicate that the reservoir fractures have experienced three major periods of tectonic movement. Regional tectonic fracture development is mainly controlled by stratigraphic lithology and stratigraphic thickness； Fault co-derived fractures are influenced by the distance from the fault and the location of the upper and lower plates of the fault. The shift in the direction of the late horizontal maximum principal stress will cause the early fractures to open or close under different conditions in the Bozi-Dabei area， which in turn affects the degree of fracture opening and effectiveness. When the horizontal maximum principal stress is deflected to intersect with the early fractures at a smaller angle or even superimpose， the fracture effectiveness of the related group system in the deflection direction is better， and the overall coordination is developed. The distribution characteristics of the fracture system in the highly productive reservoir are the result of a dominant configuration of multi-phase activities.

Based on the previous research results of the dolomite reservoir of the Permian Maokou Formation in the Sichuan Basin， the authors made a systematic geochemical analysis of the dolomite reservoir of the Maokou Formation in the Well JT1 of the Bajiaochang structure by means of thin section observation， cathodoluminescence， carbon and oxygen isotope and in-situ laser microanalysis， and discussed the genetic mechanism of the dolomite reservoir. According to the research： （1） The shoal facies dolomite reservoir of a section of Mao 2 Member of Maokou Formation in Well JT1 is mainly developed in the shoal facies deposition at the edge of the platform depression， and the development of the reservoir is controlled by the sedimentary facies belt and dolomitization. （2） There are two stages of dolomitization in the Maokou Formation. The first phase of dolomitization mainly formed fine-medium crystalline dolomite， mainly semi-euhedral to euhedral crystals， with weak cathodoluminescence intensity， mainly dark red to red light. δ¹³C VPDB value and ∑REE concentration are equivalent to those of micritic limestone， and rare earth elements have the characteristics of Ce negative anomaly and Y positive anomaly. It indicates that the dolomitization fluid is mainly confined seawater at the same period. The second stage of dolomitization forms saddle-shaped dolomite， and the intensity of cathodoluminescence is the strongest， red to bright red light， with obvious positive δEu anomaly features， high ⁸⁷Sr/⁸⁶Sr ratio， low Sr content but high Mn content， and high fluid inclusion homogenization temperature and salinity， indicating that its dolomitization fluid is deep high-salinity hydrothermal brine. （3） The dolomitization time is syngenetic - penecontemporaneous to shallow burial period， the first stage of dolomitization occurs， and Mg²⁺ in limited seawater metasomatizes sparry bioclastic limestone， forming a large number of intercrystalline dissolution pores and crystals. Because dolomite has a stronger anti-compaction effect than limestone， the pore space is better preserved； in the burial period， affected by tectonic movement， the second stage of dolomitization occurred， mainly forming saddle-shaped dolomite， filling in the pore space formed by the first stage of dolomitization. It has a destructive effect on the reservoir.

The southern Sichuan Basin is the hot spot of shale gas exploration and development in China， where there are many types of shale gas reservoirs and abundant data. In order to summarize the basic geological characteristics and laws of enrichment and high yield in that area， by using seismic， drilling， logging， testing data， we analyzed key geological factors of shale gas reservoir in the aspects of sedimentation， tectonic deformation， preservation conditions， and also analyzed characteristics， differences of enrichment condition and implications of typical shale gas reservoirs. The results show， （1）The sedimentary process controls the formation thickness， quality and thickness of reservoir in O₃w-S₁l^1-1； （2）The influence of tectonic deformation on shale gas reservoir reflects in structural style， burial depth， geostress field， characteristics of natural fracture； （3）The preservation conditions of shale gas reservoirs are affected by many factors such as the intensity of structural reconstruction， sedimentation and burial depth； （4）Shale gas reservoirs in southern Sichuan Basin can be divided into four types： type of slope， type of syncline， type of low-steep anticline with wide-gentle syncline and type of faulted anticline， while different types of gas reservoirs have different geological characteristics， enrichment conditions； （5）The geological and engineering characteristics of different types of shale gas reservoirs are analyzed and corresponding technical countermeasures are provided， which are helpful to improve the production of single well and the construction of shale gas production capacity. The research results enrich the theory of shale gas enrichment and high yield in Sichuan Basin， and provide technical reference for the large-scale and cost-efficient development of shale gas in other areas.

Affected by the breakup of Rodinia supercontinent， rift basins were widely developed in the Yangtze block， North China block and Tarim block during the Nanhua Period. The existence of deep rift basins played an important role in controlling the late tectonic evolution of the basin and the distribution of deep oil and gas. The Sichuan Basin is located in the western margin of the Yangtze block. Because there are few wells in the basin that reveal the stratigraphic characteristics of the Nanhua System， the research on the structural characteristics and genetic mechanism of the Nanhua rift in the Basin is relatively low. This paper takes the Nanhua rift in central area of Sichuan Basin as the research object， uses the method of drilling and seismic combination to analyze the geometric characteristics of the rift basin， recover the kinematic process， and preliminarily explore the genetic mechanism of the rift basin under the constraints of the regional tectonic background. The research reveals that： （1）NE trending narrow and long rifts dominated by extensionism developed in Nanhua Period in the central area of Sichuan Basin， the boundary of which is mostly “fault overthrust” or “double fault”， The internal horst graben type and ladder type faults are developed. （2）The tectonic evolution of the rift valley is divided into three main stages： the opening stage of the rift basin， the synsedimentary stage and the sedimentary overlap stage. The formation and evolution of the Nanhua rift valley has an obvious control effect on the structural deformation of the overlying strata， and then affects multiple sets of source-reservoir associations and oil and gas distribution in the basin. （3）Based on the results of previous petrogeochemical studies， it is comprehensively believed that the Nanhua rift in Sichuan Basin developed in the environment of continental crust thinning after plate subduction and collision， showing the nature of intracontinental rift. The fault activity under the extensional tectonic background is the key factor affecting the development of Cambrian carbonate hydrothermal solution reservoir and the formation of natural gas reservoir.

The western Hubei area， which is adjacent to the Sichuan Basin， have great shale gas resources potential in the Upper Permian marine shales， and have achieved a series of exploration discoveries in recent years， such as Enshi， Hongxing and other areas. However， there are many differences in reservoir performance， gas-bearing property and other enrichment conditions， hence the shale gas display effect in different regions are diverse. Taking the Wujiaping Formation II in Hongxing block and Dalong Formation in Enshi area as the research objects， the detailed characterization of shale gas enrichment differences and analysis of controlling factors have been carried out by comprehensive use of drilling， logging， seismic and laboratory analysis and testing data. The results show that： （1） The original quality of the Wujiaping Formation II is relatively similar to that of the Dalong Formation， with a slight difference in the thickness of organic shale； （2） The reservoir performance， source-reservoir coupling and gas-bearing property of the Wujiaping Formation II are better than that of the Dalong Formation； （3） The strong Meso-Cenozoic tectonic compression around the Yangtze led to earlier initial uplift of the Dalong Formation in Enshi area， resulting in greater denudation of the overlying strata， and relatively poor shale gas preservation conditions； （4） The burial depth and structural style can effectively indicate the current preservation conditions. The Wujiaping Formation II in Hongxing block that was deeply buried and developed in a wide -gentle anticline， is more conducive to shale gas enrichment than the Dalong Formation， which is shallowly buried in the complex syncline in Enshi area. There have different structural styles and preservation conditions for two sets of shale in the two areas， which bring different difficulties in exploration and development. Therefore， comparative research should be strengthened and classified practical methods should be taken from the perspective of accelerating exploration and development.

The Central Hunan Depression is an important area in southern China where shale gas exploration extends from the upper reaches to the middle reaches of the Yangtze River. And the Devonian Shetianqiao Formation is the key layer of shale gas exploration in the area. Based on the field outcrop and drilling data of Lianyuan Sag in central Hunan Depression， the geological conditions of shale gas accumulation in Shetianqiao Formation were analyzed by using the data of laboratory testing， logging and field gas-bearing monitoring. The controlling factors for differential enrichment of shale gas were discussed. And the following research results were obtained. （1） Gray black-black shale， calcareous shale and marlstone are mainly developed in the basin facies area between carbonate platforms in Lianyuan Sag. The shale with a thickness of more than 80 m， high content of organic matter（TOC>1%）， good type of organic matter （sapropelic type and humus-saproptlic type） and moderate thermal evolution degree（2.0%<R_O<3.0%）has good hydrocarbon generation conditions. （2） The Shetianqiao Formation shale is a type of siliceous shale and mixed shale with high content of brittle minerals. The shale reservoir space is dominated by inorganic pores and fractures， and it is a fracture-porosity reservoir with ultra-low porosity and ultra-low permeability. The pore volume is mainly provided by mesopores and macropores. （3） The shale gas reservoir of Shetianqiao Formation is a residual normal pressure gas reservoir. It mainly experienced three stages of forming and evolution：Early in-situ accumulation， medium-term adjustment and transformation， and late dissipation-residue. The Middle Jurassic-Early Cretaceous is the most important period of accumulation and transformation. （4） Organic-rich shale formed in deep-water anoxic environment of basin facies between platforms is the basis for gas enrichment and accumulation in Shetianqiao Formation. Good preservation conditions are the key to gas accumulation. The development characteristics of fractures and related pores controls the distribution of high-quality reservoirs and the shale gas enrichment. In conclusion， the shale gas of Shetianqiao Formation has the enrichment and accumulation pattern of “integration of source and reservoir， differential distribution， sedimentary facies controlling hydrocarbon supply and favorable area， and structure-fracture determining preservation conditions and gas enrichment”. The wide and gentle syncline structure in the basin facies area is a favorable region for gas enrichment， and the development zone of pores and fractures are favorable locations for gas enrichment.

A set of silicon-rich and carbon-rich shale reservoirs are developed in the second member of Permian Wujiaping Formation （Wu2 Member）in the Hongxing area of eastern Sichuan Basin， which have been proved to be a set of high-quality gas-bearing shale reservoir based on exploration activities. The set of shale primary quality （organic carbon content， lithology and mineralogy， sedimentary structure） has strong heterogeneity characteristics in vertical direction， directly affecting the gas-bearing property and removability of shale reservoir. Based on the establishment of shale isochronous stratigraphic correlation framework， this study systematically investigates the vertical heterogeneity characteristics of the shale reservoir in rock and mineral composition， sedimentary structure， organic matter abundance and organic matter types. The main controlling factors of heterogeneity are discussed from the aspects of sedimentation， marine paleo-productivity and redox environment. The vertical heterogeneity is mainly controlled by factors such as paleoclimate， volcanic activity and sea level rise and fall. The ancient climate and sea level fluctuations jointly control the supply of terrigenous detrital minerals， volcanic activity controls the paleo-productivity of surface seawater， thereby controlling the content of organic matter and authigenic silica， the continental volcanic activity and submarine volcano activity led to the development of tuff thin interbeds and siliceous strips and other special lithologic interbeds in shale reservoirs， which affected the modifiability of shale reservoirs themselves.

Volcano-hydrothermal effect has an important influence on the sedimentary evolution and biological source of Permian Lucaogou Formation in Jimusar Sag. The core samples of Well J305 in Jimusar Sag of Junggar Basin were collected and systematically studied by element geochemistry and organic geochemistry methods. The specific contents include geochemical characteristics of source rocks， evolution of sedimentary paleoenvironment and biological sources of organic matter. The results show that： （1）The major and trace elements in the source rock samples of the Lucaogou Formation show some differences between P₂l₁ and P₂l₂. The P₂l₁ is relatively rich in Sr， U， Fe₂O₃， MgO and CaO， and the P₂l₂ is relatively rich in V， SiO₂ and Al₂O₃.（2）The sedimentary period of the Lucaogou Formation was generally in a saline water environment. The water body of the P2l1 was deep， and the water depth of the P₂l₂ fluctuated greatly and was relatively shallow. From P₂l₁ to P₂l₂， the salinity gradually decreased. The paleo-oxygen phase is a relatively stable reducing environment， and the enrichment of organic matter is controlled by paleo-productivity， that is， biological source. Biological sources are related to paleosalinity， paleoclimate and volcanic-hydrothermal activities to a certain extent.（3）The overall characteristics of biological source composition are that the abundance of bacteria and algae is greater than that of higher plants， the abundance of bacteria is greater than that of algae， and algae are mainly green algae. Among them， cyanobacteria account for a certain proportion of bacteria，and the proportion of cyanobacteria in the P₂l₁ is relatively high.（4）The sedimentary evolution of Lucaogou Formation can be divided into five stages： arid-brackish water stage→semi-arid-brackish water stage→arid-brackish water stage→humid stage→semi-arid-brackish water stage.The sedimentary and biological sources of the Lucaogou Formation are controlled by the paleoenvironment. Volcano-hydrothermal processes provide a large amount of nutrients and improve paleoproductivity. A stable reducing environment provides the necessary conditions for the preservation of organic matter.

There are growing UHTP condensate gas reservoirs that have been discovered with the increase of exploration depth of offshore gas reservoir in recent years. The production of condensate water in these HTHP condensate fields increases significantly in the later stage of production， which makes it more difficult to analyze production dynamics and treat surface condensate water. In this study， experiments on the change of PVT water-gas ratio during development and the evaporation of formation water in long cores with decreasing reservoir pressure were conducted for three well areas in the abnormally high-pressure and high-temperature condensate reservoirs in the South China Sea. The difference of the condensate water-gas ratio of the three well areas with the decrease of gas pressure was compared， and the change characteristics of the condensate water-gas ratio obtained by the PVT test and the long core test under the formation temperature were discussed. The mechanism of formation water evaporation in long core simulating reservoir conditions is analyzed， which is higher than that in PVT cylinder. The simulation and prediction method of high-temperature condensate gas reservoir condensate water gas ratio is established and verified. The study shows： The fundamental reason why formation water evaporation in high-temperature and high-pressure condensate gas reservoir is higher than that in PVT cylinder is that the small pore diameter in the reservoir causes the critical properties of each component of condensate gas to deviate under the influence of pore diameter， which not only leads to the contraction of condensate gas in porous media， but also increases the saturated vapor pressure of formation water， resulting in the rise of dew point， and enhancing the mass transfer of formation water to condensate gas. The simulation and prediction method of formation water evaporation in high-temperature condensate gas reservoir can accurately predict the change of condensate water production.

In order to study the paleo-fluid characteristics of Devonian Shetianqiao Formation in Shaoyang Sag， central Hunan and its indication for shale gas preservation， fracture vein samples of Well Shuangdi 1 were systematically collected and fluid geochemistry， electronic probe and inclusion analysis were carried out. The results show that the δ¹³C and δ¹⁸O of calcite vein are not significantly different from those of surrounding rock. The difference between the carbon and oxygen isotopes of calcite veins and surrounding rocks are very small， the oxygen isotopes of calcite veins are smaller than surrounding rocks， while the carbon isotopes are similar to surrounding rocks， the carbon and oxygen isotopes of calcite veins are all smaller than surrounding rocks， which respectively represent three different sealing conditions： closed system with low water/rock ratio， cross layers fluid mixing and atmospheric water mixing. The closed system section with low water/rock ratio indicated by paleo-fluid is a gas show section， indicating its long-term sealing property. The Fe and Mn contents of calcite veins indicate oxidizing environment of fracture zone， which has mixture with paleo-atmospheric water. The fluid activities of the Shetianqiao Formation is characterized by multiple stages， Sm-Nd isotopic dating reveals that the formation time of vertical angle veins in the lower part of Shetianqiao Formation is 149 Ma， the formation depth is 3.2 km and with the fluid gas content is poor， indicating that the shale gas reservoir has suffered strong damage. The comprehensive study shows that the strong compression and uplift of Yanshan movement makes strong structural deformation in central Hunan， especially the fracture development， early denudation time， high intensity and unfavorable structural preservation conditions in the sag margin area. The deformation in the middle of the sag are weaker and the preservation conditions are relatively favorable， but the Devonian System was platform facies area， which was not conducive to shale development. Therefore， the shale of the upper part of Upper Devonian Menggongao Formation in the middle of Shaoyang Sag should be taken as the exploration direction， combined with sedimentary facies and cap rock thickness analysis.

The Junggar Basin is a typical superimposed basin with multiple hydrocarbon sources in western China. Five sets of gas source rock series are developed， including the Carboniferous， Permian Jiamuhe Formation， Permian Fengcheng Formation， Permian Lower Wuerhe Formation， and Jurassic. The main gas source rocks are widely distributed in the basin. Some areas are in the high over mature stage， entering the main gas generation period of gas source rocks， and have the material basis for exploring atmospheric fields. The natural gas in Junggar Basin has the characteristics of multiple sources， mixed sources and complex genesis. The conventional natural gas genesis identification indicators are inaccurate in identifying the origin of natural gas in some areas. In order to solve this problem， this paper systematically combs and analyzes the geochemical characteristics of natural gas in different layers and regions， combines the hydrocarbon generation characteristics of different source rocks， establishes a new chart for identifying the origin of natural gas， and identifies the origin of natural gas in Junggar Basin. This paper puts forward the following views： （1） It is difficult to define oil type gas in high evolution stage and coal type gas in low evolution stage in the Junggar Basin with traditional methods. Failure to effectively classify natural gas type and maturity will affect gas source identification and genesis research in this area， and new identification methods need to be established. （2） In this paper， a chart for identifying the origin and source of natural gas in Junggar Basin has been established， which can effectively identify the origin and source of natural gas in different strata and regions， and is applicable to coal type gas in low evolutionary stage and oil type gas in high evolutionary stage. （3） Plenty of oil type gas exists in the Permian Fengcheng Formation and Lower Wuerhe Formation in Mahu and Shawan in the northwest margin， and the Carboniferous， Permian Jiamuhe Formation and Jurassic source rocks also make significant contributions； Jurassic coal type gas is mainly distributed in the south of Junggar Basin from low mature to over mature stages； The eastern part and the hinterland of the Junggar basin are dominated by the coal type gas of the Carboniferous and Jurassic in the high evolution stage， mixed with some Permian oil type gas.

The two trillion square gas areas of Kela-Keshen and Boz-Dabei in the northern Kuqa Depression of Tarim Basin have entered the stage of large-scale development. In order to guide gas exploration and development efficiently， it is necessary to further refine and deepen the basic geological aspects such as sedimentation and sand body distribution. In this paper， based on the observation and measurement of outcrop section， the analysis of macroscopic lithic facies and typical sedimentary structure characteristics， and combined with underground data， the sedimentary microfacies characteristics and configuration of the skeleton sand body of the third member of Bashijiqike Formation （Ba 3 Member） in the northern Kuqa Depression are systematically studied. The results show that there are 21 types of rock facies in the Ba 3 Member of the northern outcrop area of the Kuqa Depression， which are in the front subfacies of the fan delta as a whole， and the sedimentary microfacies of the sand body are underwater distributary channel， estuary bar and far bar. The microfacies of the skeleton sand body are mainly recession-type near-shore and far-shore underwater distributary channels， of which the overall lithology granularity of the near-shore underwater distributary channel is coarse-grained （40% conglomerate and pebbly sandstone， 50% medium-fine sandstone）， and the overall lithology granularity of the far bank underwater distributary channel is finer （85% silt-fine-medium-fine sandstone， 15% sandstone in gravel）. The single layer sand body of the underwater distributary channel in the outlying area has large thickness and good lateral continuity， which is usually formed by the vertical overlapping continuous pieces of single-stage channel. The maximum thickness of single-stage composite channel sand body can reach 15-20 m， the average thickness is 7-10 m， and the lateral extension range is more than 2 km， which can form the regular model reservoir. From east to west， the sand body in the outcrop area becomes smaller and the vertical continuity becomes worse. The sand body is the most developed and the lateral continuity is the best in the maximum advance period of fan delta. The sand body configuration of the Ba 3 Member in the outcrop area is comparable to that of the well of Dabei Gas Field， and the microfacies type and size of the skeleton sand body are consistent. The study on the sedimentary microfacies and configuration characteristics of the skeleton sand body of the Ba 3 Member in the northern Kuqa Depression provides the basic geological basis for the exploration and development of deep and ultra-deep natural gas.

Lianggaoshan Formation of Lower Jurassic in Southeast Sichuan is a new field of tight sandstone oil and gas exploration with great potential. However， its strong reservoir heterogeneity and weak basic research on favorable reservoir characteristics and diagenetic evolution laws restrict exploration and development. In this paper， the Lianggaoshan Formation in Liutang area of Southeast Sichuan was taken as the research object. The diagenetic facies were classified and diagenetic evolution model of tight sandstone was established based on the study of petrology， physical properties and diagenetic characteristics combined with integrating core， cast thin section， scanning electron microscope and clay minerals. The results show that the reservoirs of Lianggaoshan Formation in Southeast Sichuan are dominated by feldspathic lithic sandstone， the reservoir properties are tight， and the reservoir space is mainly residual primary intergranular pores and intergranular dissolved pores. Diagenesis such as compaction， cementation and dissolution is developed in the reservoir， and the diagenetic stage is the middle diagenetic stage B. The reservoir in the study area mainly develops four diagenetic facies： strong compaction diagenetic facies， carbonate cementation diagenetic facies， dissolution diagenetic facies and chlorite membrane cementation diagenetic facies. The sandstone with strong compaction diagenetic facies has fine grain size， high content of plastic particles and dense physical properties. The sandstone with carbonate cementation diagenetic facies has fine grain size， high content of carbonate cement and dense physical properties. The sandstone with dissolution diagenetic faces has high feldspar content， strong dissolution and relatively good reservoir physical properties. The sandstone with chlorite film cemented facies has coarse grains， high chlorite film content， medium compaction， primary pores and dissolution pores. In conclusion， the sandstone with chlorite membrane cementation diagenetic facies and dissolution diagenetic facies are favorable reservoirs in the study area.

The objective of this study was to investigate the effects of the development degree of carbonate dissolved pores and gas injection velocity on the gas-water two-phase seepage. An interparticle-dissolved dual-pore network model was proposed using a convolution algorithm by considering the characteristics of carbonate karst pores. The proposed unsteady-state gas-water seepage model took the effects of gas compressibility and pore-scale pressure propagation into account， and it was validated by comparing the simulation results with the core-derived gas-water two-phase seepage through unsteady-state gas flooding experiments， which comprehensively characterizes the pore-scale gas-water seepage flow in pore-scale modeling. The gas flooding procedure at different injection velocity was simulated by assuming different characteristics of dissolved pores in carbonates. The results indicated that the more developed dissolved pores can bring about a wider gas-water two-phase infiltration area and a longer gas-water co-flow period. Further， the competitive balancing between the gas injection pressure and the capillary and viscous forces could also impact gas sweeping efficiency， resulting in different gas-water spatial distributions， gas injection velocity and pressures. The results provided a deep technical and theoretical view of the gas production in carbonate reservoirs， which has important significance for improving the exploitation efficiency of carbonate reservoirs.

The Well Mitan-1 obtained high-yield industrial gas flow in the fourth member of the Majiagou Formation of Ordovician（O₁m₄） in the mid-eastern Ordos Basin， which has achieved a major breakthrough in the exploration of Ordovician subsalt natural gas. However， there are disputes on the origin of natural gas in Well Mitan-1 at present. The measured results show that the natural gas in Well Mitan-1 is mainly composed of alkane gas （95.18%）， the gas drying coefficient （C₁/C_1-5）is 0.947， the content of H₂S is 3.49%， and there is also a small amount of N₂ and CO₂ in non-hydrocarbon gas. The carbon isotopic compositions of methane， ethane and propane in the natural gas are -45.5‰，-26.4‰ and -24.3‰， respectively. Based on the regional geological background， the characteristics of potential source rocks and the geochemical characteristics of natural gas， it is considered that the natural gas in Well Mitan-1 is self-generated and self-accumulated oil-associated gas in Ordovician subsalt carbonate rocks. However， there are some geochemical anomalies， such as methane carbon isotope value （δ¹³C₁） is lighter and ethane carbon isotope （δ¹³C₂） has the characteristics of coal-type gas. Combined with the thermal simulation experiment of hydrocarbon generation and the characteristics of residual gas in rocks， it is considered that the special geochemical characteristics of Well Mitan-1 are closely related to the gypsum rocks. On the one hand， the ubiquitous gypsum-rock provides a good caprock， which makes retainment of the early-generated natural gas. On the other hand， the existence of gypsum rock promotes the generation of heavy hydrocarbon gases （{\mathrm{C}}_{{\mathrm{2}}^{+}}） and H₂S. In addition， less than 5% H₂S content and higher {\mathrm{C}}_{{\mathrm{2}}^{+}} content indicate that the thermochemical sulfate reduction （TSR）， if any， should not be so strong that methane is not affected by TSR. The δ¹³C₂ may be a sensitive parameter for identifying TSR.

The sediment type and evolution are the response of peripheral plate tectonic activities， and profoundly affect the reservoir quality of shale. The sediment types and evolution of marine shale at the turn of Late Ordovician-Early Silurian were revealed by detailed description of the Wufeng Formation shale core， full-scale imaging of large thin sections and field emission scanning electron microscopy analysis of argon ion polished sections in southern Sichuan. Marine shale mainly develops three shallow-water fine-grained sediments： fine-grained turbidites， source mixing sediments and in-situ mixing sediments. The fine-grained turbidite is dominated by clastic quartz （45.5%-54.5%） and clay minerals （29.0%-38.9%）， and nine typical sedimentary sequences can be clearly seen. The source mixing sediment is mainly composed of quartz （36.5%）， carbonate （24.3%） and clay minerals （39.3%）， and carbonate minerals are mainly exogenous transport deposits. In-situ mixing sediments is dominated by clay minerals （30.5%）， ankerite （39.5%） and calcite （26.5%）， and carbonate minerals are mainly derived from in-situ. The fine-grained turbidite are mainly developed in the graptolite zone WF1-2， the source mixing sediment is mainly developed in the graptolite zone WF3， and the in-situ mixing sediment is mainly developed in the graptolite zone WF4. The sediment type and distribution reflect the characteristics and evolution of the tectonic activity of the surrounding plate. During the sedimentary period of the graptolite zone WF1-2， fine-grained turbidite developed， indicating that the tectonic compression of the surrounding plate was strong， and the terrestrial supply was sufficient. During the sedimentary period of the graptolite zone WF3， the source mixing sediment developed， indicating that the tectonic activity of the surrounding plate was weakened， and the terrestrial supply was reduced. During the sedimentary period of graptolite zone WF4， the in-situ mixing sediment developed， indicating that the tectonic activity of the surrounding plate was further weakened， and the terrestrial supply was further reduced. The sediment type directly affects the reservoir quality of shale. The porosity and total organic carbon content of fine-grained turbidite sediment are the lowest， while those of in-situ mixing sediment are the highest.

Lacustrine-delta sandstone of Lianggaoshan Formation has great potential of tight oil and gas resources in eastern Sichuan Basin. It is the key to determine diagenetic evolution and genetic mechanism of tight reservoir distribution prediction. However， genetic mechanism of Lianggaoshan Formation sandstone reservoir was still poorly understood in the eastern Sichuan Basin. Therefore， thin section， X-ray diffraction， scanning electron microscopy， physical property analysis， NMR porosity and high-pressure mercury injection were used to systematically study the petrology， reservoir space， porosity and permeability， and diagenesis. Moreover， genetic evolution mechanism of sandstone reservoir was also systematically analyzed. The main conclusions are as follows： （1） Lianggaoshan Formation sandstone mainly comprise fine-grained lithic sandstone and minor medium-grained and silty lithic sandstone with moderate sorted grains. The reservoir space mainly consists of intergranular dissolved pores， intragranular dissolved pores and primary pores. The porosity ranges from 0 to 8%， and the permeability ranges mainly from 0.001×10^-3 μm² to 0.01×10^-3 μm². （2） Diagenesis mainly includes mechanical compaction， calcite cementation， authigenic chlorite and dissolution. Calcite cements include early pore filling and late replacement of grains. Chlorite mainly occurs as grain coating. The feldspar and calcite cements were main subject of dissolution. （3） The underwater branching channel of high-level system was the mass basis of high-quality reservoir development. Mechanical compaction was the main cause of reservoir densification. The early chlorite coating can protect the pores and provide space for the subsequent precipitation of calcite cementation. The early pore-filling calcite decreased porosity by occupying the pore space. Feldspar and early calcite can produce secondary pore through dissolution. Source rock evolution can provide organic acid and for dissolution. The physical property of reservoirs at the bottom of the sandbody （the main body of sandbody） is better than those in the middle and upper part of the sandbody （the edge of the sandbody）. This study can provide important theoretical support for the reservoir prediction.

There has been very limited studies focusing on the fault system in Jurassic strata in Sichuan Basin， restricting the understanding of the hydrocarbon accumulation mode of the Shaximiao Formation and the expansion of exploration range. Based on interpretation and coherent slice analysis of abundant seismic data， it is newly discovered that normal faults are widely developed in northern central Sichuan Basin in Jurassic strata. These faults mainly extend from Lower to Upper Jurassic strata， and is characterized by the continuous arrangement of NEE-trending small faults in the plane， while a few NNE-trending and NNW trending faults are developed. The Jurassic fault combination are different in the basin， where the normal faults are mainly distributed in the low uplift of the central Sichuan and the north of central Sichuan. According to the comparison of geochemical data， the normal faults could communicate the Jurassic source rocks and Shaximiao Formation reservoir in these areas. The newly discovered normal faults are superimposed with the middle and Lower Jurassic source rocks in the northern central Sichuan Basin. A new hydrocarbon accumulation model of hydrocarbon generation from the middle and lower Jurassic and normal faults communication could be formed. Among these areas， multi-stage channel superimposed development zone near normal faults is one of the favorable exploration directions.

Tight tuffaceous sandstone is a special type of tight sandstone. Its pore structures and porosity permeability relationships are quite different from those of conventional tight sandstone. It is difficult to classify and evaluate the tight tuffaceous sandstone by using conventional reservoir classification methods. This paper studied the tight tuffaceous sandstone of Yingcheng Formation of Dehui fault depression in southern Songliao Basin， where Nuclear Magnetic Resonance （NMR） and high pressure mercury injection are the main means. Pore structure characteristics of tight tuffaceous sandstone are analyzed and the differences with conventival tight sandstone are compared. Correlation analysis was adopted where R₅₀ （The throat radius corresponding to the mercury saturation of 50%） and movable fluid saturation are selected as the key parameters to establish a comprehensive new evaluation model for reservoir classification of tight tuffaceous sandstone. Results demonstrate that premium tight tuffaceous sandstone develops intergranular and intragranular dissolution effective pores， has noticeable right-sided T₂ spectrum distribution and high movable fluid saturation， while inferior tight tuffaceous sandstone mainly has tuffaceous dissolution pores and intercrystalline pores and left-sided T₂ sepctrum. In addition， the pore structure characteristics were analyzed by means of high pressure mercury injection and constant velocity mercury injection， and four typical mercury injection curves were identified，i.e.， large pore-tiny throat， middle pore-tiny throat， middle pore-micro throat and small pore-micro throat. The corresponding tuffaceous content gradually increases， and it was believed that the main reason for poor correlation between porosity and permeability was that tuff blockes key throats and then decreases permeability. Pore structures between tight tuffaceous sandstone and conventional tight sandstone are compared and analyzed. Tight tuffaceous sandstone developes more tiny pores， has worse porosity-permeability correlations， less effective storage capability and connectivity than conventional tight sandstone. R₅₀ and movable fluid saturation are adopted and tight tuffaceous sandstond reservoirs are divided into type Ⅰ，Ⅱ，Ⅲ reservoirs and dry reservoir， where the classification results coincide with the testing results.

The breakthrough of oil and gas exploration in the eastern Mahaidong structure of the northern margin of the Qaidam Basin reveals that the Jurassic source rocks in this area have strong oil and gas potential. This paper presents a detailed comparative analysis of geochemical indicators such as abundance， type and maturity of hydrocarbon source rocks developed in different depressions， and on this basis， the controlling factors of the differences in hydrocarbon generation potential are discussed. It is found that： （1）The Jurassic hydrocarbon source rocks in this region are mainly distributed in the fifth and seventh members of the Middle Jurassic Dameigou Formation， dominated by carbonaceous mudstone and dark mudstone or shale， respectively， among which the source rocks in the seventh member have higher abundance and are dominated by type Ⅰ-Ⅱ Kerogen， which is the key layer of source rock developed in this region； （2）The quality of source rocks in Hongshan depression is the best， and the thermal evolution has reached the mature stage， which is expected to be the key block for the next step of increasing storage and production； Yuka and Xiaochaidan depressions are followed by Hobson and Delingha depressions with poor quality； （3）The differences in the abundance and types of source rocks in the seventh member of different depressions are related to the sedimentary environment： the Hobson Depression developed lakeshore-swamp sediments in this period， while the Hongshan， Xiaochaidan and Yuka depressions were shallow-semi-deep lake， and the abundance and types of source rocks in the former are poor； （4）The difference of source rock maturity among different depressions is controlled by tectonic activities： Hobson， Hongshan and Delingha depressions are continuous subsidence depressions， while Yuka and Xiaochaidan depressions are tectonic reverse transition depressions. The former has high source rock maturity while the latter has relatively low maturity. This study has important guiding significance for the next oil and gas exploration deployment in Qaidam Basin.

Previous researchers have carried out researches on reservoir characteristics and reservoir-forming conditions of the Loushanguan Group giant thick dolostone of Cambrian in the northern Qianbei Depression， but the studies on its geochemical characteristics and paleo-marine environment are still weak. Based on field investigations， this paper analyzed the lithological and isotopic characteristics of the Loushanguan Group， and then discussed the paleo-marine environment and evolution. The results show that the ordering degree of dolomite ranges from 0.63 to 0.91， with an average of 0.78， and the dolomite content is basically above 95%， with relatively low detrital mineral content. The δ¹³C values of the rocks range form －1.94‰ to 2.78‰， with an average of -1.02‰. The δ¹³C values distributed within the carbon isotopic composition of middle to late Cambrian seawater. The evolution trend of the δ¹³C curve shows that the sea level was relatively low and fluctuated frequently during the early to middle stages of sedimentation. A higher level transgression occurred in the middle period. Accompanied by low-frequency and low amplitude oscillations in the seawater， the sea level gradually decreased in the middle and late stages of sedimentation.The values of δ¹⁸O is －8.32‰-－6.24‰， with an average of －7.19‰， which is slightly positive compared with Cambrian seawater and Cambrian limestone. The strontium isotope ⁸⁷Sr/⁸⁶Sr values range from 0.709 45 to 0.710 33， which is significantly higher than the Sr isotopic composition of seawater in the same stage. This anomaly may be related to the diagenetic reformation by the Sr rich fluids from the lower strata during the deep burial period. The paleo-salinity index Z values are mainly distributed in the range of 120.02‰ to 129.65‰， with an average of 121.63‰， indicated that the Loushanguan Group deposited in salinized seawater. The surface temperature of seawater was concentrated between 18 ℃ and 23 ℃， with an average of 21.17 ℃， indicating that the main part of Loushanguan Period was a hot subtropical climate. The clay mineral assemblage in the stratigraphy showed strong evaporation， and the sedimentary water was a high salinity alkaline medium. The Th/K ratio is distributed between 3 and 6， indicating that the overall energy of the seawater was low. The U/Th ratio fluctuates between 0.75 and 1.25， reflecting the oxygen-poor characteristics of paleo-marine. The paleo-environmental elements are well coupled with the sedimentary features， and the sedimentary features of Loushanguan Group reflected the unique global climate and paleo-marine conditions of the period. The above achievements have important theoretical and practical implications for the reconstruction of the Cambrian paleoenvironmental and paleo-ecological evolutionary history of the Yangzi Plateau and the world.

When there is a low-velocity or high-velocity layer in the formation， a strong reflection interface usually occurs， and the weak reflection signal of the reservoir is shielded by the strong reflection signal， and the seismic profile shows a strong event， which reduces the accuracy of reservoir prediction. Therefore， it is of great significance to remove the shielding effect of strong reflection on weak reservoir signals. According to the sparse signal decomposition theory， this paper proposes a method of removing strong seismic reflection using soft threshold based on dynamic dictionary decomposition. Firstly， the dynamic dictionary is established by using the Ricker wavelet， and the seismic strong reflection waveform is decomposed into the sparse representation of the dynamic dictionary. Then soft threshold method is used to remove the components of the dynamic dictionary with large amplitude， so as to achieve the purpose of removing the strong reflection. Compared with the traditional strong seismic reflection removal method， this method can better improve the lateral discontinuity after the removal of strong reflections. It also reduces the dependence on strong reflection horizon， and no longer requires accurate strong reflection horizon data. The test of physical model data and the application of actual data show that this method can effectively remove the shielding effect of strong reflection and highlight the effective signal of the reservoir.

To address the difficult problem of poor understanding of the reservoir mobilization law of water-bearing sandstone gas reservoirs， a multi-point piezometric physical simulation experiment method and apparatus were used for long cores. Six natural matrix cores with permeability levels of 0.047，0.064，0.154，0.175，0.602， and 1.74×10^-3 μm² were selected， and a series of physical simulation experiments of depletion extraction were conducted under the conditions of water content saturation of about 0%，30%，40%，50%，60%， and 70%， respectively. The effects of reservoir matrix permeability and water saturation on the instantaneous gas production， pressure drop curve and characteristics of the reservoir， as well as the degree of reserve utilization （R） at different development stages （end of steady production， abandonment conditions and ultimate conditions） were investigated. The results show that： （1） the gas production capacity of reservoir matrix and the degree of reservoir utilization are controlled by both reservoir matrix permeability and water content saturation， but the sensitive threshold value is different in different stages of gas reservoir development. （2） Based on the characteristic diagram of the degree of utilization under the abandoned condition， a set of reserve utilization classification evaluation boundary map is constructed with the reservoir permeability and water content saturation corresponding to 60% and 80% of the reservoir utilization degree respectively as the indexes， and three levels of priority utilization， conditional utilization and potential utilization are divided， and the reservoir parameters corresponding to each level are clearly defined， which can provide prospective guidance for prioritizing and determining the sequence of reservoir utilization for high-quality reservoirs in the field.