Significant breakthrough in petroleum exploration has been obtained recently in the Ordovician strata in the eastern Shunbei area， Tarim Basin， which is benefit from the identification of fault-controlled carbonated fracture-vuggy reservoir and prediction of its distribution. As the exploration moves into westward area， the development of multiple sets of complex intrusive rock in the Upper Ordovician has caused poor seismic imaging， which has great impact on the identification of fractures and reservoirs in the Middle and Lower Ordovician and restricts the exploration process in this area. Based on the drilling， 3D seismic data and regional geological background， this study established a variety of complex intrusions and fracture-vuggy reservoirs model and carried out seismic refection forward modelling of Middle and Lower Ordovician reservoirs on the basis of detailed study of the characteristics of intrusions developed in the Upper Ordovician in the Shunbei area. According to the study， the intrusive rock not only leads to the disjunction of phase at the edge of the intrusion in the seismic profile， but also forms pseudo-faults in the Upper Ordovician underside. In addition， the nearly horizontal thick-bedded， multi-layered intrusions can also cause the formation of multiple waves in the Middle and Lower Ordovician. Furthermore， the multiple waves can strength the amplitude of the beaded reflection caused by the fractures and cavities， which increase the difficulties in the re-cognization of the favorable reservoirs. By combining forward modeling and seismic attributes， the fault identification method is defined， both of the relationship between intrusive rock thickness and amplitude and the influence degree of intrusive rock on reservoir imaging are quantified， all of which can greatly improve the reliability of fault identification and the accuracy of reservoir description， thus provide a geophysical basis for the next exploration deployment.

Although the sedimentary environment of the Chang 7 shale of Yanchang Formation in the Ordos Basin has been extensively studied， it remains a topic of ongoing debate， especially in the northern margin of the basin. This is due to the highly heterogeneous nature of the lacustrine shales and the substantially different depositional environment. To address this issue， we collected shale cores from the Well F75 located in the northern part of the Ordos Basin， and systematically measured the biomarker proxies， aiming to provide new insights into this debate. The results show that the Chang 7 source rocks in the northern part of the basin have high organic carbon contents， with an average TOC of 4.58% and an average S ₁+S ₂ of 18.03 mg/g. The organic matter is primarily type II₁， indicating that the studied samples can be categorized as the premium source rocks. The thermal history across the entire well shows that the samples are mostly in the low maturity stage， with some being immature. Among all the samples， those in the Chang 7₃ sub-member have relatively higher organic matter abundance， maturity and hydrogen index， allowing them to have better hydrocarbon potential. Biomarker compounds show that the Chang 7 Member was， in general， deposited in a reducing freshwater sedimentary environment. Additionally， the C₂₇-C₂₈-C₂₉ sterane distribution indicated that the organic matter of Chang 7₁ and Chang 7₂ was mainly derived from phytoplankton， while that of Chang 7₃ instead mainly derived from mixed sources， particularly in a specific depth. In the middle section of Chang 7₃ sub-member， there is a significant shift in the organic matter source and sedimentary environment. The organic matter is unexpectedly dominated by terrigenous higher plants， and the reducibility of the water body is shown to be weakened. This change reflects a high influx of terrigenous material， which may be linked to enhanced flood events due to warm and humid climate. When comparing the shales from the southern and northern margins of the basin， it is clear that the gammacerane index value is higher in the southern， with higher C₂₇ sterane content and lower C₂₉ sterane content. In the southern margin， the water body was relatively stable with higher salinity， more pronounced stratification， and predominantly planktonic organic matter serving as the primary source for the organic-rich sediment. Additionally， widely deposited volcanic ash is evident along the southern margin. Hence， the varied sedimentary conditions along the northern and southern margins of the Ordos Basin account for the different organic matter enrichment. The pronounced volcanic events close to the southern margin introduced substantial nutrient influx， fostering prolific primary productivity， including algae and plankton， which led to relatively high organic matter accumulation. In contrast， the notable terrigenous influx along the northern margin diluted the organic matter content， with a relatively greater contribution from higher plants.

Pore structure characteristics are the main factor affecting shale reservoir， and its qualitative and quantitative characterization and main controlling factors are key issues in shale reservoir research. In order to explore the differences in microscopic pore structures and main controlling factors of different sedimentary microfacies of deep shale reservoir， this paper selects the Wufeng-Longmaxi formations in Well Z301 of Zigong area in southern Sichuan Basin as an example， based on systematic experiments such as core， thin section， scanning electron microscopy observations， X-ray diffraction analysis， organic geochemical analysis， N₂/CO₂ adsorption， high-pressure mercury injection， the vertical heterogeneity of pore structure in the O₃ w-S₁ l ₁ shale reservoir is analyzed. The research results indicate that the sedimentary microfacies of the O₃ w-S₁ l ₁ shale reservoir in the study area can be divided into three categories from bottom to top： strong reducing， high carbon， calcium-rich， and silicon rich deep-water continental shelves （microfacies ①）， weak reducing-medium carbon-calcium containing-silicon mud mixed-deep water continental shelves （microfacies ②）， and weak reducing-weak oxidizing-low carbon-siliceous mud-semi deep water continental shelves （microfacies ③）； among the three types of microfacies， macropores are mainly inorganic pores， while mesopores and micropores are mainly organic pores. Mesopores and micropores are also the main pore types that control the volume and specific surface area of shale pores； the development degree of different pore types varies among the three microfacies； mesopores and micropores are the most important pore type that controls reservoir physical properties and gas content； TOC and the content of clay minerals are the key factors affecting the pore structure of deep shale. Quartz has a slightly weaker controlling effect on nanoscale pores， while carbonate minerals have no significant controlling effect on nanoscale pores； the characteristics of high TOC， low clay minerals， and high brittleness minerals in microfacies ① determine that it is the most commercially valuable lithofacies for mining. The relevant conclusions can provide guidance for enriching the high-yield patterns of deep shale gas enrichment.

The Qiongzhusi Formation of Cambrian （∈₁ q） in Sichuan Basin is the most favorable strata for exploration and development of shale gas besides the Wufeng Formation of Ordovician （O₃ w） and Longmaxi Formation of Silurian （S₁ l）. Taking the middle part of Deyang-Anyue rift trough as the research object， meanwhile utilizing existing seismic， drilling， logging， experimental data， this paper has analyzed the basic characteristics of ∈₁ q shale gas reservoirs， and has analyzed the differences between shale gas reservoirs of ∈₁ q and S₁ l in southern Sichuan Basin， and also has provided technical support for evaluation of layers， optimal selection of advantageous areas in ∈₁ q. The main conclusions are as follows： （1） There are differences in sedimentary paleogeomorphology of ∈₁ q， which can be divided into three kinds of sedimentary paleogeomorphology in trough， slope and outside zone of trough， which control the thickness distribution and quality of shale reservoir. （2） In the middle part of Deyang-Anyu rift trough， the sedimentary environment is superior， and the preservation conditions are good； the structure is simple， the thickness of reservoir is large， and the horizontal stress difference between two directions is small， which are conducive to reservoir reconstruction； the buried depth of the target layer is large， which brings challenges to the implementation of the project. （3）The evaluation of layers and optimal selection of advantageous areas of ∈₁ q should follow the overall idea of “vertical stratification and horizontal zonation”. In the vertical direction， the black shale of layer⑤ should be the main target of the current research， and gradually expand to other layers； in the plane direction， the paleogeomorphic region of the trough and slope should be the main areas to be explored at present， and gradually expand to the zone outside the trough.

“全国沉积学大会”是由中国地质学会沉积地质专业委员会、中国矿物岩石地球化学学会沉积学专业委
员会发起的四年一届的全国性学术会议， 是全国沉积学界交流的最高学术平台。第八届全国沉积学大会定
于2025 年4 月22—25 日在北京市举行。本次大会共设置7 个议题，33 个专题。其中专题5-E2“陆相细粒沉
积及资源效应”：面向陆相细粒沉积及资源效应基础理论前沿和热点，包括不同类型湖盆细粒沉积发育机理
与有机质富集模式，构造—气候等重大地质事件对湖盆细粒沉积发育、有机碳埋藏的影响，有机—无机相互
作用与细粒沉积成岩、生烃差异，陆相页岩油储层形成与富集等前沿科学问题和陆相页岩油勘探面临的关
键问题。
为集中探讨陆相细粒沉积及资源效应基础理论前沿和热点，加速推动细粒沉积及其油气资源的勘探开
发与产业化发展，专题召集人一致同意，在《天然气地球科学》组织“第八届全国沉积学大会：陆相细粒沉积
及资源效应”专辑，就陆相细粒沉积及资源效应等相关研究及应用撰文讨论，以期开拓新的研究思路，加强
学科交叉与学术创新。专辑拟定于2025 年下半年以正刊形式在《天然气地球科学》刊出。
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（3）陆相细粒沉积岩形成机理与发育模式；
（4）有机—无机相互作用与陆相细粒沉积成岩—生烃演化；
（5）陆相页岩储层形成机理；
（6）陆相页岩油富集机理与勘探开发进展。
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2025 年4 月30 日。
4. 会议/专辑召集人
邱 振 高级工程师 中国石油勘探开发研究院 qiuzhen316@163.com
梁 超 教授 中国石油大学（华东） liangchao0318@163.com
刘忠宝 高级工程师 中国石化石油勘探开发研究院 liuzb.syky@sinopec.com
卞从胜 高级工程师 中国石油勘探开发研究院 biancongsheng@126.com
杨伟伟 正高级工程师 中国石油长庆油田分公司 yww1_cq@petrochina.com.cn
李一凡 副教授 中国地质大学（北京） liyifan@cugb.edu.cn
孙平昌 教授 吉林大学 sunpc@jlu.edu.cn
吴 靖 教授 山东科技大学地球科学与工程学院 wujing6524982@163.com
王永超 高级工程师 中国石油大庆油田勘探开发研究院 wyc0168@126.com
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In recent years， the Middle Jurassic Shaximiao Formation in the Qiulin-Jinhua and Bajiaochang structures in the central Sichuan Basin has become a hot spot of exploration. However， the origin of tight gas in the Shaximiao Formation in the study area remains unclear. In this study， the hydrocarbon generation potential of source rocks was evaluated based on total organic carbon content （TOC） and Rock-Eval pyrolysis of thirty-seven mudstone samples from the Da’anzhai Member of the Lower Jurassic Ziliujing Formation， the Lianggaoshan Formation， and the Upper Triassic Xujiahe Formation. Moreover， nineteen gas samples from the Shaximiao and Xujiahe formations were analyzed using gas chromatography and isotope ratio mass spectrometry to determine their origin. The results show that mudstones from the Da’anzhai Member and Lianggaoshan Formation are good source rocks at the mature stage， with type Ⅱ₁-Ⅱ₂ kerogen， TOC content ranging from 0.48% to 2.79% （average 1.30%）. In contrast， the mudstones of the Xujiahe Formation are mature–highly mature hydrocarbon source rocks， with type III kerogen and variable organic matter abundance. Most gas samples from the Qiulin-Jinhua areas show similar characteristics to those from the Xinchang Structure in western Sichuan Basin， indicating mature-highly mature coal-type gas sourced from the Xujiahe Formation with minor Jurassic contributions. The Bajiaochang area is dominated by mature coal-type gas and mixed gas sourced from the Xujiahe Formation and Jurassic source rocks， while the Gongshanmiao area produces oil-type gas from Jurassic sources. Regionally， Jurassic source rock contributions to Shaximiao Formation gas increase from west to central Sichuan Basin， controlling gas reservoir distribution. Coal-type gas of the Shaximiao Formation in Qiulin-Jinhua area may be transported laterally primarily from western Sichuan Basin via faults and fluvial sandstone reservoirs， supported by the similar gas maturity of gas and accumulation timing to the Shaximiao Formation reservoirs in western Sichuan Basin. In the Bajiaochang area， faults connecting the Shaximiao Formation reservoir with both the Xujiahe Formation and Jurassic source rocks are well-developed， resulting insignificantly increased proportions of mixed gas. Thus， fault-mediated vertical transmission represents a critical pathway for natural gas charging in this area.

At present， all the helium used in industrial development comes from the crustal-derived helium in the helium-rich natural gas reservoir. Natural gas is the carrier of crustal-derived helium， and its generation， accumulation， and helium release are closely related to the tectonic thermal evolution of the basin. It is important to systematically evaluate the influence of tectonic thermal evolution on the helium release in a basin to clarify the enrichment of natural gas and helium. The Weihe Basin， as the first sedimentary basin with helium mining rights in China， is rich in helium gas resources. This article takes the Weihe Basin as an example to systematically simulate the tectonic and thermal evolution history of the basin. At the same time， it deeply analyzes the occurrence characteristics of hydrocarbon source rocks and helium source minerals， estimates the amount of helium resources generated and released by the main helium source minerals in the Huashan rock mass， and explores the impact of basin tectonic and thermal evolution on the enrichment of helium rich natural gas reservoirs. The aim is to provide new ideas for the establishment and improvement of a helium resource investigation and evaluation system. The results show that： （1） The crustal-derived helium gas in the Weihe Basin mainly comes from helium source minerals rich in U and Th elements such as zircon， apatite， etc.， which are relatively scattered in rocks. The temperature range （>180 ℃） where natural gas is generated in large quantities and the main helium source minerals release helium gas has a high degree of overlap. （2） After the formation of the basement， the Weihe Basin underwent Paleozoic sedimentation and was subsequently strongly uplifted and eroded. A large number of Indosinian and Yanshanian granite bodies were formed on the surface， in which helium source minerals rich in uranium and thorium elements （mainly calcite， zircon， and apatite） continuously decayed to generate helium gas and partially enclosed the helium gas in the mineral lattice. The faulting of the Cenozoic era led to rapid subsidence of the basin since approximately 40 Ma， followed by accelerated subsidence around 5 Ma， resulting in rapid warming of the strata. Natural gas was generated from Paleozoic source rocks， and helium gas generated from helium source minerals was released in a concentrated manner. The two have a spatiotemporal coupling relationship. During the migration process， natural gas continuously carries scattered helium gas into traps， thereby forming helium rich natural gas reservoirs. （3） According to the helium sealing temperature of the main helium source minerals and the characteristics of helium gas accumulation in many basins with helium rich natural gas， the helium sealing zone （<60 ℃）， partially sealing zone （60-220 ℃） and unsealing zone （>220 ℃） can be divided.

Recently， a number of wells such as YT1H and ZT1 in the Ordos Basin have made new discoveries of natural gas in the Permian Taiyuan Formation limestone， revealing that the limestone of the Taiyuan Formation has good exploration potential. However， there are still problems such as unclear reservoir genesis mechanism and key reservoir formation mode in the Taiyuan Formation limestone， which seriously restricts the further gas exploration and deployment of this layer. Therefore， based on the abundant core， thin section and physical property data of Taiyuan Formation， this paper systematically studies the relationship between the development of limestone reservoir and the early exposed karst， and establishes the karst reservoir control model in the early limestone diagenesis. The results show that： （1） The early diagenetic karstification mainly developed in granular limestone and mostly located in the middle and upper part of the upward shallower sequence. The identifiable karst features include fabric selective dissolution， solution fissure/solution gully， solution speckle， karst breccia and multi-phase exposed surface， etc. （2） The intensity of karstification in single cycle gradually increased from the bottom to the top. The karst at the bottom of the cycle was weak， with local development of chip mold holes， while the karst reconstruction scope expanded upward. Dominant channels and dissolution mottling began to develop， and the karst process was moderate. In contrast， the upper karst system in the cycle cleaved and dissociated the bedrock， developed karst breccia， and exhibited overdeveloped karst processes. （3） Under the control of exposure time， high and low frequency cycles are developed in the study area， and the exposed surface of high frequency cycles is mostly found in limestone， which is an“episodic” cycle interface， and the inner karst intensity is manifested as karst non-development → selective degradation of bioclastic debris → dominant channel and dissolution spots， while the low frequency cycle interface only appears at the top of the slope section or Maergou section of the limestone， and the inner karst intensity is manifested as dominant channel → dissolution spots → karst breccia. （4） The high-quality limestone reservoir mainly developed in the middle and upper parts of the quaternary cycle， that is， the moderate karst reconstruction area， and the reservoir quality of the lower part of the cycle and the top part of the cycle became significantly worse. It is believed that the multi-stage karst in the early diagenetic stage not only controls the development and distribution of limestone reservoirs in the study area， but also greatly improves the reservoir and seepage capacity， which is the key factor for the formation of limestone reservoirs in Taiyuan Formation.

The Ordos Basin is a key area for coal reservoir development in China. The deep coal reservoirs of the Benxi Formation in the northeastern part of the basin exhibit significant thickness， making them favorable targets for deep coalbed methane exploration. Through core observation， coal quality analysis， and pore structure characterization of planar samples from the No.8 coal reservoir in the Benxi Formation， this study investigates the coal quality and distribution characteristics of deep coal reservoirs， elucidates their genetic mechanisms， and provides theoretical guidance for optimizing coalbed methane exploitation. The deep coal reservoirs in the Ordos Basin show strong planar heterogeneity. From the tidal flat-swamp to the lagoon-swamp depositional systems， ash content gradually decreases， while thermal maturity， sulfur content， and vitrinite-inertinite ratio increase with increasing distance from the proximal source area within the lagoon-swamp system. This indicates that the tidal flat-swamp coal reservoirs formed in a relatively oxidized environment with substantial terrigenous clastic input， whereas the lagoon-swamp system developed under deeper water columns and more reducing conditions influenced by marine transgression-regression cycles. Pore development in the tidal flat-swamp system is inferior to that in the lagoon-swamp system， with better connectivity observed in distal areas of the latter. Micropores （predominantly 0.6 nm in diameter） dominate pore volume， followed by macropores， suggesting micropores are the primary pore type. The deep coal reservoirs are synergistically controlled by terrigenous clastic input and thermal evolution. In the tidal flat-swamp system， clay mineral infilling from clastic materials degrades reservoir quality， while in distal lagoon-swamp areas， reduced clastic influence and higher thermal maturity enhance hydrocarbon generation， promoting gas pore formation and improving reservoir properties. Consequently， the distal lagoon-swamp system represents the most favorable zone for natural gas exploration in the No.8 coal reservoir of the Benxi Formation.

Fracture bodies usually develop in the slip fault systems in sedimentary basins， and the fractures have strong concealment， and traditional fracture identification techniques do not perform well. Existing fracture interpretation strategies for target layers usually adopt a local view， ignoring the overall characteristics of fracture body fractures. Through the use of the U-ResNet deep learning model， all strata of the Zhenjing Block in Ordos Basin were identified for fractures. Combined with dip-guided seismic attribute slices， the formation mechanism， periods and levels of fractures were revealed， and for the first time， the NWW slip distance was estimated. By analyzing the extension characteristics of deep fractures， it was confirmed that the three groups of NWW-oriented slide fractures in the southern part of the block are essentially flower structures， and their rootstock extended to the basal fractures， confirming the reactivation of basal fractures in multiple tectonic movements. The cross-section and plan style of Chang 8 fracture body were divided， and a diamond-pulling rift was identified on the NEE fracture， providing seismic evidence for the NEE fracture slip movement. In addition， three spindle-depression fracture combinations were found， explaining the formation reasons of staggered-step faults， and giving the favorable combination style of fracture bodies and their distribution positions on the plane. The study shows that the application of deep learning fracture technology and a full-view interpretation strategy helps to reveal the development characteristics and evolution rules of complex high-angle slip fracture bodies.

The Nanjiang area in the northeastern Sichuan Basin is a low exploration area in the pre-mountainous belt of the Micang Mountains. And Well A1 drilled a natural gas reservoir without clear principle in the Xujiahe Formation. To distinguish the hydrocarbon accumulation model of gas fields in the fourth member of the Xujiahe Formation， the curvature of the stratum top surface and abnormal signals of well logs and seismic attribution have been carried out. Through these studies， the direction of the tectonic stress and fractured reservoirs which are controlled by curvature are identified. It is indicated that the distribution of the gas field is controlled by the distance of the Micang Mountain and the Daba Mountain. Where the Micang Mountain and the Daba Mountain stress together is the favorable zone. Fractures were developed with the relative curvature >0.2， and more fractures were open with the relative curvature >0.4. However， the gas would be dissipated if the fractured reservoir was controlled by faults. After compaction， cementation and densification， the fractures can be used as geological desserts to enrich natural gas in the fourth member of the Xujiahe Formation. With the orogenic movement of the Daba Mountains， the fractures were developed due to tectonic movements where the relative curvature was high. Hydrocarbon charged into the fracture traps of the fourth member of the Xujiahe Formation.

Marine-terrestrial transitional shale gas is another important strategic replacement resource after the commercial development of marine shale gas. Marine-terrestrial transitional shale has the characteristics of strong heterogeneity， rapid depositional phase change， and complex lithology combination. Geological theories of marine shale gas can not be fully applied to marine-continental transitional facies， and the controlling factors of shale gas enrichment in the marine and continental transition facies are not well understood， which restricts efficient exploration and development. Taking the Shan₂ ³ sub-member shale in the Daqi area of the eastern margin of the Ordos Basin as an example， the geochemical characteristics and reservoir characteristics of shale were investigated through experiments such as microscopic analysis， gas adsorption， high-pressure mercury intrusion， breakthrough pressure， diffusion coefficient， and overburden pore permeability. This research elucidated the controlling factors of shale gas accumulation in marine-continental transitional facies. The research results indicate that the Shan₂ ³ sub-member shale in the marine-continental transitional facies exhibits high organic matter abundance， high maturity， and predominantly humic-type characteristics. The pore types are mainly dominated by inorganic mineral pores， with relatively fewer organic pores and microfractures. The conclusion suggests that the enrichment of marine-continental transitional facies shale gas is primarily controlled by a combination of organic matter abundance， pore size， lithological composition， and structural evolution. High organic matter abundance enhances the adsorption capacity of shale， providing more adsorption sites for methane gas molecules in micropores. The combination of shale-coal and shale-ash favors the in-situ enrichment of shale gas. Stable tectonics and appropriate burial depth facilitate the preservation of shale gas. Furthermore， an evolutionary model for the storage and sealing capacity of marine-continental transitional facies shale gas in the Dagang area has been established. The above findings can provide geological theoretical guidance for sweet spot prediction and rapid development of pilot test areas for marine-continental transitional facies shale gas.

The Middle Permian Maokou Formation in Shunan area is one of the main reservoirs in Sichuan Basin， but due to the variety of the reservoir types in the area， the natural gas has a complicated distribution pattern， and the characteristics of the reservoir formation and evolution are still unknown. This study clarifies the source of natural gas through the analysis of natural gas components and carbon isotope characteristics. It also determines the timing of oil and gas charging by examining fluid inclusion characteristics， along with typical tectonic features and single-well burial history-thermal evolution history. By integrating drilling and seismic data， the study reconstructs the tectonic morphology of the Maokou Group during the key period of oil and gas formation， and analyzes the oil and gas formation evolution in the study area in terms of the coupling between the formation evolution of the ring closure and the oil and gas injection. The results show that： （1） The natural gas of Maokou Formation in Shunan area has a CH₄ content greater than 95%， with low H₂S content， which is a typical dry gas， and is the cracking gas of crude oil in the high-over-matured stage； it is mainly originated from the hydrocarbon source rocks of Longmaxi Formation of the Lower Silurian， with a mixture from the hydrocarbon source rocks of the Maoyuan section of the Middle Permian at the same time. （2） There are five stages of hydrocarbon accumulation in Shunan Maokou Formation， i.e.， the initial formation stage of Late Triassic-Early Jurassic paleo-oil reservoirs； the massive filling stage of Middle Jurassic-Late Jurassic paleo-oil reservoirs； the formation stage of Late Jurassic-Early Cretaceous paleo-oil reservoirs in the third stage； the formation stage of Early Cretaceous-Middle Cretaceous paleo-gas reservoirs in the fourth stage； the stage of Late Cretaceous paleo-gas reservoirs adjusting and stabilizing stage since the fifth stage. （3） During the Late Indo-Cretaceous–Early Yanshan period， the development of Luzhou ancient uplift played a crucial role in the formation of early ancient oil reservoirs. These reservoirs were concentrated in the tectonic high points， exhibiting characteristics of “ancient oil reservoirs gathered in high places during the Indo-Cretaceous period”； In the early to middle Yanshan period， with continued deep burial， the tectonic high part of the ancient uplift continued to charge， while crude oil gradually began to crack. This period marks the evolution stage of ancient oil and gas reservoirs. In the Late Yanshan period， the ancient uplift of Luzhou gradually disintegrated and continued to be buried deeply， the ancient oil and gas reservoirs were transformed into ancient gas reservoirs， with the characteristic of “Yanshan period ancient oil reservoirs cracked into gas”； from the Xishan period to the present day， the ancient uplift of Luzhou completely disintegrated， and under the control of tectonic movement and ancient uplift of the Xishan period， the ancient gas reservoirs underwent adjustments and stereotypes， and formed the present-day gas reservoirs with the characteristic of “weak adjustment of Xishan period” and the characteristic of “weak adjustment of ancient oil reservoirs”. The Xishan period is characterized by “weak adjustment and enrichment of gas reservoirs”.

The Ma 5₄ ^1a sub⁃layer of Ordovician is a key gas-producing interval in the Ordos Basin. Through comprehensive analysis of core analysis， physical property determination， high-pressure mercury injection， nuclear magnetic resonance and dynamic production data， the characteristics of carbonate reservoirs in the target intervals were studied， and the lower limits of their physical properties were discussed， thus providing a theoretical basis for the exploration and development of carbonate gas reservoirs in the Yanchang Gas Field. The results reveal that the carbonate reservoir in the northern part of the Ma 5₄ ^1a sub⁃layer is predominantly composed of mud crystalline dolomite and fine crystalline dolomite， with a well-developed network of intercrystalline pores， dissolution pores， vuggy dissolution pores， microfractures， and dissolution fractures. The main reservoir type is characterized as a pore-fracture-pore system. The petrophysical log responses of the reservoir indicate high acoustic time differences （147-210 μs/m）， high neutron porosity （5%-18%）， low natural gamma values（8-40 API），low density（2.4-2.8 g/cm³），low effective photoelectric absorption cross-sections（2.5-4.2 b/e），and relatively low resistivity （40-800 Ω·m）. These features suggest that the reservoir is a low-porosity， low-permeability carbonate system. To further refine the understanding of its petrophysical limits， several analytical methods were employed， including empirical statistical analysis， bound water saturation assessment， mercury injection parameters， distribution function methods， and gas testing. A petrophysical model for porosity and permeability was established and validated using dynamic production data. These findings are critical for optimizing the exploration and development strategies for carbonate gas reservoirs in the region.

Breakthrough progress has been made in the exploration of deep-seated coal-rock gas in the Carboniferous Benxi Formation in the Yichuan area of the Ordos Basin， and a number of appraisal wells have gained high-yield industrial gas flow， which confirms that the deep-seated coal rock gas resources in this area have the potential for large-scale development. However， there are fewer systematic studies on the reservoir characteristics of deep-seated coal-rock gas in this area， and the laws of reservoir characteristics are not well understood. Based on this， this study selected the No.1 coal seam of the Benxi Formation as the research object， and systematically investigated the characteristics of the coal-rock-gas reservoir of the Benxi Formation in terms of lithology， physical properties， pore-fracture development， and gas-bearing properties by synthesizing the experimental data of core observation， scanning electron microscope analysis， and physical properties testing. Research results show： （1） The coal body structure of No.8 coal of Benxi Formation is dominated by primary structural coal， the macroscopic type is dominated by bright coal and semi-bright coal， the microscopic group is dominated by specular group， the ash content is low， the average value is 12.76%， and the maximal reflectivity of specular body is from 2.04% to 2.53%， and it is dominated by anemic and anthracite， which is at the high maturity gas generation stage. （2） The reservoir type of No.8 coal in Benxi Formation is dominated by intergranular pores， cytosolic pores， cast pores， pneumatic pores and fissures， and some of the pores are filled by clay minerals or calcite， of which the fissures include macroscopic cuttings and microscopic fissures； the pore fissures are mainly micropores， followed by microcracks； the specific surface area is dominated by micropores， followed by macropores. （3） The physical properties of the No.8 coal of Benxi Formation show low porosity， with porosity ranging from 4.22% to 4.96% and averaging 4.59%； permeability ranging from 0.02×10^-3 μm² to 3.48×10^-3 μm² and averaging 1.21×10^-3 μm²， and the coal rock has good permeability in the stratigraphic state. （4） The adsorption capacity of No.8 coal of Benxi Formation is strong， with an air-dried basis Langmuir volume of 21.25–31.34 m³/t （averaging 27.61 m³/t） and a Langmuir pressure of 1.98–3.77 MPa （averaging 3.08 MPa）. The adsorption capacity of the coal rock has a negative correlation with the ash content， and a positive correlation with the maturity degree. The results not only provide quantitative evaluation indexes for the preferred selection of deep coal gas sweet spot in Yichuan area of Ordos Basin， but also reveal the new exploration direction of deep coal system unconventional gas reservoirs.

To elucidate the provenance of intricate deep crude oils in the Lower Paleozoic strata， in this paper， a systematic geochemical analysis of Lower Paleozoic source rocks and crude oil samples in Tarim Basin has been carried out. The juxtaposition of samples subjected to natural evolutionary processes and thermal simulation experiments unveiled that certain aromatic indices exhibit remarkable stability， particularly 1-alkyl-2，3，6-aryl isoprenoids （2，3，6-AIPs）， which demonstrates pronounced resistance to anti-secondary-alteration. A comprehensive assessment of the hydrocarbon generation potential of Lower Paleozoic source rocks identified five series of organically enriched strata （Lower Cambrian Yuertus Formation （Є₁ y）， Middle-Lower Ordovician Heituao Formation， Middle Ordovician from the Xihexiu section， Middle-Upper Ordovician Sargan Formation， and Upper Ordovician Lianglitage Formation）. These were categorized into three distinct groups：“low salt-green algae”，“high salt-dinoflagellates”， and “photic-zone euxinia （PZE）-green sulfur bacteria （GSB），” predicated on the presence of stable aromatic biomarkers， including 2，3，6-AIPs. And crude oils were categorized into two distinct groups： PZE-green algae oil and PZE-GSB oil. Notably， PZE-GSB source rocks （mainly developed from the Є₁ y） contained abundant 2，3，6-AIPs， showing similarity to almost all crude oils from the Tazhong and Tabei areas， Tarim Basin. Through oil-source correlation and the quantitative deconvolution of mixed crude oils， it was ascertained that the source rock harboring 2，3，6-AIPs likely plays a pivotal role in the substantial contributions to the extant deep crude oil reserves in the Tarim Basin. Therefore， finely determining the spatial distribution of this source rock developed under the special biological-environmental condition （PZE-GSB）， in the next stage， would provide significant reference for the targeted exploration of deep complex crude oil in the Lower Paleozoic from the Tarim Basin and even the world.

The Upper Paleozoic tight sandstone gas in the western Ordos Basin has become a key area for the increase of natural gas reserves and production in the basin. The Taiyuan Formation， as a newly explored layer in the western Ordos Basin， has demonstrated significantly superior gas test and production performance compared to the 8th member of the Shihezi Formation and the Shanxi Formation above it. In order to clarify the natural gas enrichment law of Taiyuan Formation， the main controlling factors of natural gas enrichment in Taiyuan Formation were determined by using logging， analytical test and three-dimensional seismic data， and through the study of coal-measure source rock evaluation， sedimentary reservoir characteristics， structural characteristics， etc. Research has shown that the main hydrocarbon source rock of Upper Paleozoic Benxi Formation in the Yanchi area has a hydrocarbon generation intensity of （10-24）×10⁸ m³/km²， and the middle-eastern part of the study area has a high hydrocarbon generation intensity； a new understanding of the development of barrier coastal sedimentation in the Taiyuan Formation has been proposed for the first time. The distribution of barrier sand bars is stable， with an average thickness of 10.2 m. The reservoir is homogeneous， and the rock type is quartz sandstone， with an average porosity of 7.6% and an average permeability of 1.12×10^-3 μm²； multi-phase faults are developed， which are not penetrated to the Shiqianfeng Formation. In particular， the Hercynian faults connect the gas source rocks at the bottom， constitute a favorable migration channel for natural gas， and improve the physical properties of the reservoir； the higher the intensity of hydrocarbon generation， the more faults in Hercynian and the closer the distance， the better the physical properties of the reservoir， and the more enriched the natural gas. The research results can provide reference for natural gas exploration with the same geological characteristics in Ordos Basin.

To systematically study the development characteristics and transformation modes of clay minerals in alkaline lake shale， and explore the development of clay minerals in alkaline lake sedimentary environments， Based on scanning electron microscopy （SEM） observation and X-ray diffraction， this paper investigates the characteristics and dynamic transformation of clay minerals in different sedimentary environments of the Fengcheng Formation shale in Mahu Sag. In the sedimentary center of the alkaline lake， only a small amount of clay minerals （<5%） are developed， mainly characterized by smectite （S） and illite-smectite mixed layers （I/S）. The detrital clay minerals were dissolved in a strongly alkaline diagenetic environment， transforming into authigenic silicate minerals such as K-feldspar. Moreover， the presence of CO₃ ^2－/HCO₃ ^－ can delay the transformation of clay minerals in the sedimentary center. In the edge slope zone， the content of clay minerals （average 11.57%）， which is mainly the illite （I）， chlorite （C）， and I/S is higher than that in the sedimentary center. The diagenetic environment is transformed from strongly alkaline to weakly alkaline-weakly acidic， and the primitive detrital clay minerals have not been dissolved and can be preserved in the early diagenetic stage， and illitization and chloritization occurr with the increase of stratigraphic temperature and pressure. The transformation of clay minerals can produce many brittle minerals such as authigenic quartz and K-feldspar， which not only increases the brittleness of shale reservoirs but also generates secondary pores and fractures， and is beneficial for the exploration and development of shale oil and gas.

Understanding dynamic desorption characteristics and seepage mechanisms in deep coalbed methane （CBM） reservoirs is critical for optimizing drainage strategies and enabling large-scale development. Taking the coal of the Benxi Formation in Ordos Basin as the object， the dynamic production behavior is analyzed and a mathematical model for desorption of adsorbed gas from continuous coal matrix and gas-water two-phase flow in discrete fractures. The model was solved using the finite element method. Based on simulation results， gas migration patterns during drainage were analyzed and desorption characteristics in water-saturated coal and their impact on gas production were discussed. （1） The sensitive pressure， turning pressure， and starting pressure of the CBM are 1.87 MPa， 4.77 MPa， and 7.15 MPa， respectively. （2） CBM desorption continues to expand from the near-wellbore region to the reservoir boundary. After 500 days （1.4 years） of production， the entire reservoir pressure declines below the critical desorption pressure. （3） After 1 725 days （4.7 years）， desorption efficiency transitions from low-efficiency to high-efficiency desorption， and gas production shifts from free gas dominance to primarily adsorbed gas contribution. （4） Daily gas production strongly correlates with desorption behavior within 100 m of the wellbore. Stabilizing near-wellbore desorption efficiency maintains stable gas production. The conclusions will provide theoretical support for the formulation of optimization measures of drainage and production system.

The deep CBM （coalbed methane） industry of Chine has ushered in an important period of development opportunities， and it is imperative to accelerate the efficient development technology of horizontal wells. In this study， based on the coal characteristics and logging response， drilling parameters， the K coefficient is established from the aspects of coalification degree， physical property， structure， and gas-bearing property， and the coal reservoirs of Benxi Formation in the eastern Ordos Basin is divided into three types. The K coefficient of class I reservoir is more than 2， which is composed of cataclastic bright coal， primary bright coal and cataclastic semi-bright coal. The contribution rate per meter of the class I reservoir can reach three times that of the class III reservoir. The cataclastic structures are superior to primary structures. The cataclastic coal generally has better drill ability， permeability and gas content， which has a high proportion in the Class I reservoirs. Comprehensively considering the geological conditions such as coal thickness， the drilling encounter rate of coal， and the fracturing intensity， it is clearly that class I reservoirs are the “black gold targets” for the development of CBM in the horizontal wells and are the main cause for productivity. The 1 500 m horizontal length， 500 m class I reservoir length， 4-6 t/m sand intensity are the lower limits of the economic development with 5.5×10⁴ m³/d production. If the class I reservoir length exceeds 1 000 m， under the same horizontal length and fracturing intensity， the production of horizontal wells can economically increase with 7.0×10⁴ m³/d. Based on the geology， structure and reservoir types， this paper summarizes the coal-rock sedimentary models into three types： high coalification + gentle structure， transitional coal-rock + micro-structure， and cataclastic coal + complex structure. The first two models are suitable for large-scale deployment of cluster horizontal well groups， fully utilizing geological reserves and releasing production capacity. The model of cataclastic coal + complex structure has huge gas-bearing potential， which will be the key target for increasing the production of horizontal wells in the future.The guidance of horizontal well is a key process control for enhancing the drilling encounter rate of “black gold targets”. This paper proposes that the drilling quality of horizontal wells can be identified according to the changes of K coefficient， and the drilling decision can be adjusted in time. This technology will promote the iteration of coal guidance technology to “black gold target” guidance technology， and help the high-quality development of deep CBM.

The study of the development characteristics and formation mechanism of high-quality reservoirs is a key issue in understanding the formation and evolution of medium-deep buried reservoirs， and is also an important foundation for the efficient exploration and economic and effective development of tight sandstone oil and gas reservoirs. Based on drilling core， logging data， porosity-permeability， thin section， SEM and other analytical data， the development characteristics and influencing factors of high-quality reservoirs in the 8th member of Shihezi Formation （He 8 Member） in the eastern Ordos Basin were studied. The results show： Firstly， the He 8 Member mainly develops three types of reservoir petrology： quartz sandstone， lithic quartz sandstone and lithic sandstone. Quartz sandstone and lithic quartz sandstone have better physical conditions and are potentially high-quality reservoirs. Secondly， sedimentation is the basis for the development of high-quality reservoirs in the He 8 Member， which is mainly manifested in the fact that the coarser the particles of the clastic components， the better the sorting， and the higher the content of rigid particles， the more favorable the preservation of the original intergranular pores. Thirdly， diagenesis is a crucial factor in the development and evolution of tight reservoirs. During the early rapid burial process of the He 8 Member， strong mechanical compaction and intense deformation of plastic particles resulted in a significant loss of pore space in the sandstone， which is the main cause of the formation of a tight physical background. Carbonate， clay minerals and siliceous cementation at different diagenesis stages block the pore-throat space of particles， further deteriorating the physical properties of the reservoirs. Meanwhile， under conditions of relatively low rock debris content， selective dissolution effectively improves the reservoir performance of tight sandstone and plays a positive role in the formation of high-quality reservoirs. Fourthly， the pore evolution pattern indicates that， under the influence of early rapid burial， the reservoir of the He 8 Member underwent strong compaction during the early diagenesis A1 stage， forming a tight physical background. Dissolution is mainly developed during the middle diagenesis A2 stage， which is the main period for the development of secondary pores， while the middle diagenesis B stage marks the late authigenic cementation stage， where some residual intergranular pores and dissolution pores are filled， leading to further densification of the sandstone.

The gas-water distribution relationship of Cretaceous Bashijiqike Formation in Kelasu tectonic belt，Tarim Basin is complicated， the source and genesis of formation water is still unclear. Based on major and trace elements， hydrogen and oxygen isotopes， strontium isotope， combined carbonated cement carbon and oxygen isotopes， homogenization temperature and salinity of inclusions， the source and origin of formation water are deeply studied， The result show that the Bashijiqike Formation is a highly mineralized CaCl₂ formation water， and the hydrochemical parameters indicate that the formation water has experienced strong metamorphism， and the formation is well sealed， which is conducive to oil and gas preservation. The original sedimentary water of the Cretaceous Bashijiqike Formation was affected by infiltration and mixing of atmospheric precipitation， evaporation and concentration， water-rock reaction， and salt-layer water. The present formation water is characterized by Na⁺ and Ca²⁺ enrichment， Mg²⁺ depletion， δ¹⁸O enrichment， elevated ⁸⁷Sr/⁸⁶Sr ratios and low 1/Sr values. Three stages of carbonate cement are mainly developed in Bashijiqike Formation， and the iron-bearing calcite/dolomite filled in late pores and fractures is formed via organic acid decarboxylation during mesodiagenesis， the formation temperature of the iron-bearing carbonate cement is consistent with the salinity desalination of fluid inclusions caused by late hydrocarbon charging. According to the analysis of burial history， oil-gas charging history and structural evolution history， the evolution of Cretaceous formation water goes through four main stages： （1）The original sedimentary water of Bashijiqike Formation in the early sedimentary period； （2）Atmospheric precipitation intrusion and mixing at the end of Cretaceous deposition； （3）Marine incursion and saline lacustrine infiltration； （4）Source rock desalinated water intrusion. The water-rock reaction during burial always affects the chemical properties of formation water.

It’s the first deep marine gas reservoir discovered in the Middle Triassic Leikoupo Formation in Xinchang area in the latest round of marine hydrocarbon exploration in the western Sichuan Basin. There has been controversy over the understanding of the gas source of this gas reservoir for years. Based on the geochemical data of natural gas from the latest round of drilling， combined with hydrocarbon conveyance conditions， the analysis of the origin and source of natural gas in the fourth member of Leikoupo Formation in Xinchang area was carried out. The research results indicate that there are differences in natural gas composition and hydrocarbon isotope characteristics of alkane gas between the upper and lower reservoir sections of the fourth member of Leikoupo Formation gas reservoir in Xinchang area， as well as different structural position. The higher H₂S content may be related to its relatively strong TSR reaction in the lower reservoir section. The east part of the gas reservoir may have its source from continental or marine-continental coal type gas. The natural gas in the central and western of Xinchang area is mainly characterized by marine oil-type gas with relatively high maturity， corresponding to the development of relay remote source transport system， indicating that the natural gas mainly come from Permian source rocks， with partly coming from the Leikoupo Formation source rocks； While the natural gas in the northeast of Xinchang area is mainly mixed from marine and continental source gases， with relatively low maturity， corresponding to the development of the near source conveyance system of the orthogonal joint on the top of the Leikoupo Formation， indicating that the natural gas mainly comes from the source rocks of the Leikoupo Formation and Maantang-Xiaotangzi formations.

Mixed sandstones in lacustrine are characterized as thin layer， fine grain size， intense cementation and interlayer， these are found in the upper part of the Da'anzhai section of the Jurassic Ziliujing Formation in the Longgang area of the central Sichuan Basin. However， the degree of reservoir space development and exploration potential of these sandstones is unclear. To clarify the diagenesis and reservoir modification， a comprehensive study was conducted using petrology and geochemistry. The results indicate that the Da'anzhai mixed sandstones in central Sichuan Basin underwent modification during the early and middle stages of diagenesis. Constructive diagenesis is mainly caused by the three stages of acid fluid promotion of pore/fracture formation， organic acid dissolution of clay mineral impurities to form granular quartz， and fracturing caused by overpressure of fluid associated with hydrocarbon generation and expulsion， and recrystallization. Destructive diagenesis involves physical/chemical compaction and the filling of pores/fractures with cementitious materials such as clay minerals， quartz enlarged edges， dolomite， and calcite associated with the enrichment of CO₂ in various diagenetic stages. Although the Da’anzhai mixed sandstone in central Sichuan Basin is generally dense， the incomplete filling of fractures， dissolution of micro-pores， and intercrystalline pores contribute to the relative porous reservoirs. This research can provide support for the optimization of favorable intervals in tight oil exploration.

Significant breakthroughs were made in the exploration and development of the Weirong area. Taking the Longmaxi shale as the object， we analyzed its gas-bearing characteristics and main controlling factors by means of XRD and on-site gas content test. The results are as follows： the area develops low-carbon-carbon rich shale， which is at the high-over-mature stage. The average total gas content is 2.78 m³/t， and the present desorption gas is mainly free gas， with an average of 2.25 m³/t， and the average adsorption gas is 0.53 m³/t. Carbon-rich mixed siliceous shale is the dominant lithology. There is a positive correlation between the TOC content， pore structure， and their respective gas contents， and at the same time the TOC content affects the pore structure， so that the TOC content is the main controlling factor. Therefore， TOC content is the main controlling factor and pore structure is the direct factor. Clay content is negatively correlated with gas content， and R _O content is positively correlated with gas content.

Reservoir solid bitumen has been found in many petroliferous basins in the world， and it contains important information such as hydrocarbon generation， expulsion time from source rocks， and timing of paleoreservoir oil cracking. In recent years， Re-Os isotope dating is widely used in the study of solid bitumen. However， the interpretation of Re-Os isotopic ages is often ambiguous， and their geochemical significance remains unclear. This study combines isotope geochemistry and organic petrology to analyze solid bitumen from three different locations in the Upper Yangtze region. The results show that the Lower Cambrian bitumen from Songtao area has a Re-Os age of 195 ± 20 Ma， and it represents the time of bitumen solidification and the upper limit of the time when the shale of Niutitang Formation of Lower Cambrian stops hydrocarbon generation. The Dengying Formation bitumen from Jinsha area has a Re-Os age of 297 ± 20 Ma， which represents the time of bitumen solidification. The Dengying Formation bitumen from the Weiyuan Gas Field has a Re-Os age of 342.8 ± 4.7 Ma， and it also represents the time of petroleum generation. In this research， the relationship between solid bitumen Re-Os data and the thermal evolution of organic matter is discussed. It is considered that solid bitumen Re-Os data may represent the time of petroleum generation， time of hydrocarbon accumulation， and the time of bitumen solidification or the time of thermochemical sulfate reduction （TSR） completion， which ultimately depends on the genesis of solid bitumen and the homogeneity of Os in the system.

With the great breakthrough of deep coal-rock gas exploration in central and western China， Turpan-Hami Basin， which is rich in coal resources， has been paid more and more attention. However， there is a lack of research on deep coal-rock gas in Turpan-Hami Basin， which seriously affects the exploration and implementation of coal-rock gas in the basin. Based on the distribution of coal-rock in the whole basin， combined with the analysis and comparison of maceral components and trace elements of coal-rock samples in the basin， the results show that： （1） The main layer of deep coal-rock gas exploration in the Turpan-Hami Basin is the second member of the Xishanyao Formation， especially the thick coal seam at the bottom of the second member， and the coal accumulation center is located in the northern part of the Taibei Depression. （2） Vitrinite is the main component of the maceral of the main coal seam， and the content of inertinite is high in some areas. Through the identification of the maceral facies， five types of coal facies are identified in the second member of Xishanyao Formation. （3） Based on the distribution range of trace element values of typical coal facies， the paleoenvironmental characteristics of different coal facies during the coal accumulation period are defined， and the coal facies distribution map of the main coal seam in the whole basin is established based on the distribution interval values of different sensitive trace elements. In Turpan Depression， the open water swamp phase and deep water forest swamp phase are mainly developed. （4） From the perspective of paleosedimentary environment and coal-forming plants， the hydrocarbon generation of coal rocks in different coal facies is analyzed， and it is pointed out that the coal-rocks in deep forest swamp facies and open water swamp facies have good gas potential. The research results provide effective guidance for the exploration target layer and selection zone of coal-rock gas in the Turpan-Hami Basin.

Sanhu Depression is the most important biogas-producing area of the Quaternary in Qaidam Basin， with huge natural gas resources. In order to clarify the depositional environment for the formation of mudstone reservoirs in gas reservoirs and provide a basis for reservoir sweet spot evaluation， this paper analyzes the elemental geochemical characteristics and sedimentary environment of mudstone core samples from Wells ST1 and ST2 in Sebei area of Sanhu Depression through hand specimen analysis， microscopic observation and elemental testing. The findings reveal that samples from Wells ST1 and ST2 are predominantly composed of dark mudstone and siltstone， interspersed with dolomite in block， band， and laminar forms. They contain a great number of snails and plant fragments， reflecting the sedimentary environment of shallow lakes and semi-deep lakes. It has the characteristics of low silicon， weak supersaturation of aluminum， low potassium sodium， rich in magnesium and calcium， enrichment of Ba， Sr and Rb， and loss of Zr， Hf and Ni. The ICV and CIA indices， along with Th/SC-Zr/Sc discriminant maps， suggest that the Quaternary mudstone in the Sebei area underwent only mild to moderate weathering and remained largely unaffected by sedimentary sorting or recycling processes. Parameters such as Ceanom， &U， and δCe indicate that the deposition period is the environment for the transition from reduction to oxygen deficiency. The ratios of Sr content to Th/U and V/Zr are indicative of a saline water to brackish water environment. Moreover， the MAP and LST parameters， as well as Sr/Cu， Zr/Rb ratios collectively reflect a cold and dry paleoclimatic environment with weak hydrodynamics. The high soluble organic matter content of Quaternary mudstone in the Sebei area of the Sanhu Depression， coupled with frequent changes in sedimentary water environments， has resulted in distinct vertical sand-mud interbedded characteristics， forming a favorable reservoir cap combination and facilitating the formation of mudstone biogas reservoirs.

Significant breakthroughs have been made in the exploration of marine-continental transitional shale gas in the eastern Ordos Basin， but the related research obviously lags behind that of marine shale gas. Taking the Zhaoxian shale samples from Benxi Formation in Hengshan-Wupu area in the eastern Ordos Basin as the research object， the characteristics of the Zhaoxian shale reservoir in the area were comprehensively characterized by comprehensive experiments such as vitrinite reflectance， total organic carbon（TOC）， thin section， scanning electron microscopy （SEM）， X-ray whole rock diffraction （XRD）， pore permeability， low-temperature liquid nitrogen adsorption， methane isothermal adsorption， gas content and mechanical properties tests in this paper. The effects of pore structure parameters and TOC content on the adsorption capacity of shale were discussed， and the exploration potential of the Zhaoxian shale in the study area was finally comprehensively analyzed. The results show that： （1） Zhaoxian shale in the study area is a typical marine-continental transitional shale， with complex rock and mineral composition， high clay minerals and felsic minerals， with an average proportion of 47.4% and 36.4%， respectively； （2） The organic matter types of Zhaoxian shale are mainly Types I₂ and III kerogen， with high maturity and an average organic matter content of 5.30%. The organic-rich shale accounts for a relatively high proportion and has strong gas generation capacity. （3） Micro-nano scale fractures and pores are developed in Zhaoxian shale， and micro-fractures are developed in both organic matter and inorganic minerals， with fracture widths ranging from 0.01 to 1 μm. The pore types of liquid nitrogen adsorption were mainly narrow pores， with an average pore size of 13.67 nm，an average specific surface area of 6.56 m²/g， and an average total pore volume of 0.0176 cm³/g. BET specific surface area is positively correlated with the fractal dimension of pore structure， and negatively correlated with the average pore size. （4） The pore permeability of Zhaoxian shale is low， with an average Langmuir volume of 3.14 cm³/g， an average gas content of 1.52 cm³/g， an average brittleness index of 0.526， an average Young's modulus of 40.88 GPa， and an average Poisson's ratio of 0.22. （5） The Zhaoxian shale reservoir conditions in the study area are generally comparable to Shan 2 Member in Daning–Jixian area， with superior resource conditions， good transformability， and large shale gas exploration potential.

The Ordos Basin is rich in natural gas resources， and its helium resource potential has been confirmed in the Yimeng Uplift， Weihe Basin and other regions. However， the characteristics of natural gas helium content and the main controlling factors of enrichment in other areas of the basin need to be clarified through further geological exploration and scientific research. Through the collection of natural gas samples from typical wells in the southwest of Ordos Basin， and the analysis of natural gas composition， helium isotope， major and trace elements of rocks， combined with the simulation of single well geological history， temperature and pressure evolution history， the distribution characteristics， sources and main controlling factors of helium in the Upper Paleozoic of Qingyang Gas Field in Ordos Basin were analyzed， and the helium enrichment model was established. The results show that the helium content of the Upper Paleozoic in Qingyang Gas Field is 0.068%-0.310%， and the average helium content is 0.154%， which is a medium-high helium gas reservoir. The helium distribution shows a trend of low in the north and high in the south. The helium gas in Qingyang Gas Field is a typical crust source， which mainly comes from Archean-Proterozoic basement metamorphic rock-granite series， supplemented by sedimentary helium source rock. Helium enrichment is mainly controlled by central paleo-uplift， formation temperature and formation pressure， basement fracture and tectonic movement. The central paleo-uplift makes the basement shallowly buried. The basement-type helium source rock is the main and the sedimentary-type helium source rock is supplemented to provide sufficient helium. The basement fracture provides a channel for the vertical migration of helium. Low formation pressure and high formation temperature are conducive to helium dissolution. The “seesaw” tectonic movement controls the direction of natural gas migration and accumulation， forming a multi-source helium enrichment model under the background of paleo-uplift.