Helium is an important strategic resource that plays an irreplaceable role in aerospace， medical imaging and high-tech manufacturing.Noble gases have three major sources： crust， mantle and atmosphere， and their isotopic characteristics vary greatly among reservoirs， which can effectively reveal the crust-mantle evolution and the interactions between the various layers， and provide an important tool for tracing the enrichment process of “weak source” helium. Here it summarized the studies on the noble gas isotopic characteristics in typical helium-rich areas such as Hugoton-Panhandle in the U.S. and the oil and gas fields in the northern margin of Qaidam Basin in China， as well as the hot springs in the Tanzanian rift zone and the geothermal gas in the Weihe Basin in China. The results show that the helium-rich reservoirs were discovered in petroliferous basins in China and most of the ³He/⁴He ratios that are currently valuable for industrial exploitation in the world show a crustal source， i.e.， they are generated through the alpha radioactive decay of helium source elements such as uranium and thorium. In addition， the ²⁰Ne/³⁶Ar ratios that are currently valuable for industrial exploitation in the world show a crustal source， i.e.， they are generated through the alpha radioactive decay of helium source elements such as uranium and thorium. In addition， the ²⁰Ne/³⁶Ar ratios and isotopic concentrations of ²⁰Ne and ³⁶Ar in different reservoirs are quite different， suggesting that the helium-rich reservoirs have undergone different oil-gas-water equilibrium processes， and helium enrichment is closely related to the transportation of the groundwater and main gas components. The positive correlations between ⁴He and ²⁰Ne in hydrocarbons and N₂ gas reservoirs rich in crust-derived helium indicate that the enrichment of ⁴He in gas reservoirs may be closely related to groundwater， and that helium should be dissolved in groundwater before being exsolved into the gas reservoirs. Besides， mantle-derived CO₂ reservoirs are usually small in size and the process of helium enrichment may be due to the nature that CO₂ can be easily dissolved in groundwater or be mineralized into carbonate minerals， resulting in the decrease of CO₂ concentration and the increase of the relative abundance of helium. In the end， four favorable conditions for helium reservoir formation were further put forward： sufficient helium sources from ancient cratons and U-T-rich granites， development of new tectonic activities，existence of groundwater systems and free gas phases， and moderate recharge of the main gas components in the reservoir relative to helium gas.

The coal seams of Shanxi Formation and Benxi Formation of Upper Paleozoic in Yan'an Gas Field are developed， and the burial depth is generally more than 2 000 m. The coal seams are widely distributed and have great exploration and development prospects， which can provide strong support for future deep coalbed methane exploration and research. In this study， 5^# coal seam and 8^# coal seam in the deep part of typical wells in Yan'an Gas Field were selected for high-precision coalbed methane field analysis experiments. Through a variety of experimental methods and means， the characteristics of coal and rock reservoirs， differential gas-bearing characteristics and their main controlling factors were studied in depth. Four evaluation units were divided in the eastern， central， western and southern areas of Yan'an Gas Field. Taking 5^# coal seam and 8^# coal seam as the main evaluation layers， the potential of deep coalbed methane resources in Yan'an Gas Field was evaluated by various resource evaluation methods. The results show that the thickness of 5^# coal seam is thin， with an average of 1.6 m； the thickness of 8^# coal seam is relatively large， with an average of 2.3 m. The coal and rock of 5^# coal seam and 8^# coal seam are characterized by ultra-low porosity and ultra-low permeability reservoirs. The pore development is mainly affected by organic matter and minerals， resulting in complex pore structure characteristics. The 5^# coal seam and 8^# coal seam have high organic carbon abundance， large porosity and permeability， and high vitrinite content， indicating that they have strong adsorption， good reservoir physical properties and pore connectivity. The coal rock has entered the stage of dry gas generation， and the potential of coalbed methane resources is large， which is conducive to the formation of coalbed methane reservoirs with high abundance. The four selected old natural gas wells are all successfully ignited， indicating that the deep coalbed methane potential of 5^# coal seam and 8^# coal seam is great. Through the volume method and analogy method， the coalbed methane resources of 5^# coal seam and 8^# coal seam in Yan 'an gas field are calculated to be （2.96-3.54）×10¹² m³，and the coalbed methane resources are calculated by Delphi method weight to be 3.06×10¹² m³， which shows the high exploration potential of deep coalbed methane in Yan'an Gas Field. It is concluded that the 5^# coal seam and 8^# coalbed methane in Yan'an Gas Field have good accumulation conditions and great exploration and development potential， and are expected to become the replacement resources for the continuous and stable production of the gas field.

In recent years， the natural gas exploration of Paleozoic bauxite reservoir in Longdong area of Ordos Basin has made important breakthrough， and it is urgent to study the main controlling factors of the development of bauxite gas reservoir accumulation. In order to reveal the tectonic factors of bauxite gas reservoir formation， the tectonic controlling factors of bauxite gas reservoir accumulation were discussed through the analysis of structural development， faults and structural features， palaeogeomorphology and micro-palaeogeomorphology. The results show that： （1） The formation of bauxite gas reservoir in Longdong area is mainly controlled by long-term tectonic uplift， Hercynian faults， and low and slow fault stepped belt distribution on the slope background. （2） The bauxite gas reservoir is mainly distributed in the micro-palaeogeomorphological units of buried pits on the karst highland palaeogeomorphology， the net negative topography composed of main and secondary grooves on the karst slope palaeogeomorphology， and the shallow depression on the karst depression palaeogeomorphology. The lithologic assemblage， development degree and distribution characteristics of bauxite gas reservoir are different in different geomorphological units. （3） The accumulation and enrichment of bauxite gas reservoir are controlled by local structural traps developed near the faults. In the bauxite gas reservoir developed area， the local forward structural traps formed by the paleo-modern structure， such as low-micro amplitude anticline， fault anticline， and fault nose， are the main places for bauxite gas reservoir accumulation. In this paper， the development law of bauxite reservoir and gas reservoir in the eastern region of Longdong is studied and expounded， which also plays a guiding role in the exploration of similar areas and other special lithologic reservoirs.

Recent exploration has shown that the Ordos Basin has a good potential of helium resource. However， its distribution and resource calculation method are still controversial， which impede the understanding of the helium enrichment rule and subsequent exploration in the Ordos Basin. Therefore， we systematically studied the Changqing oilfield helium contents， distributions， and its resources. The results show that helium in Qingyang，Yichuan and western Sulige gas fields are above the industrial and enriched helium standards，which have the helium contents of 0.121%-0.204%（averagely 0.144%），0.060%-0.177%（averagely 0.086%） and 0.018%- 0.168%（averagely 0.053%），respectively. In contrast， Yulin， Jingbian， Shenmu， and Zizhou-Mizhi gas fields generally have relatively lower helium concentrations （averagely 0.034%）. Such distribution characteristics reveal that the content of helium in the margin of the basin is higher than that of the center. Vertically， the highest helium appears in the Permian and the lowest appears in the Ordovician. According to the new established helium resources evaluation method， the calculated in-situ helium production of He-8 and Shan-1 reservoirs is 6.27×10⁶ m³ and 1.39×10⁶ m³ respectively， accounting for 52.69% and 3.11% of the total helium production， which means the external source rocks is the main contributing source area of helium. The helium production of the metamorphic basement， sedimentary sequences， and Indosinian magmatic plutons in the southwestern margin of the basin is 2.14×10¹⁰ m³， 1.44×10¹⁰ m³， and 1.74×10⁷ m³， respectively， with total helium resources of about 358×10⁸ m³.

“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。
请感兴趣的专家学者积极参会，并投稿。
1. 专辑征稿范围（包括但不限于）
（1）重大地质事件与陆相细粒沉积；
（2）多圈层相互作用与湖泊异常高有机质沉积富集；
（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。
2. 征稿要求
（1）稿件类型为综述与评述、研究论文。撰稿规范及要求可到《天然气地球科学》官网主页“下载中心”
下载（http：//www.nggs.ac.cn/CN/column/column8.shtml）。
（2）所有稿件均将严格按程序执行，不符合发表要求的稿件将被退回。录用后的稿件会优先在线出版。
（3）论文应为作者具有原创性且尚未发表过的科研成果总结；主题鲜明、观点明确、论证有据、层次清
晰、表述专业；稿件基础资料、数据等信息，需符合有关单位/部门的保密要求。
3. 投稿截止日期
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
5. 投稿方式
登陆《天然气地球科学》官网 http：//www.nggs.ac.cn 进行投稿。投稿时请备注“第八届全国沉积学大
会：陆相细粒沉积及资源效应”专辑。投稿成功后请将稿件信息告知会议/专辑召集人或联系人。
6. 专辑联系人
李小燕 0931-8277790 lixy@llas.ac.cn
 

The exploration efforts have confirmed the presence of a bauxite gas reservoir in the Taiyuan Formation within the Longdong area， Ordos Basin. This reservoir exhibits unique characteristics， is characterized by its “small and fertile” nature， and holds significant exploration potential. However， accurately predicting the thickness and variability of the bauxite rock formation poses challenges. In order to comprehend the distribution patterns of bauxite within the Taiyuan Formation in Longdong area， a variety of techniques， including drilling， logging， and three-dimensional seismic data analysis， were employed. Bauxite lithofacies types were classified， and the controlling influence and modes of karst ancient landforms on lithofacies types and distribution were investigated. Qualitative and quantitative predictions of bauxite distribution within the Longdong area， using seismic response and intersection analysis of bauxite’s rock physical properties， were conducted. The findings indicate that karst paleogeomorphology predominantly governs the lithofacies belt of bauxite in Longdong area， with subtle paleogeomorphology and sea level fluctuations directly impacting the size and lithofacies combination of bauxite rock. Four distinct types of bauxite were identified across the karst highlands and basins： reverse cyclic bauxite， bimodal bauxite， normal cyclic bauxite， and dense bauxite. By leveraging amplitude type attributes and seismic inversion techniques， more accurate predictions regarding bauxite distribution can be made. The bauxite deposits in Longdong area are primarily concentrated in the northern regions of Ningxian， Heshui County， the southwestern portion of Qingcheng County， and the Huanxian area. Taking into consideration factors such as thickness， structure， and fractures， a total of 613 km² of favorable areas for bauxite exploration have been evaluated.

The breakthrough in natural gas exploration of the Taiyuan Formation bauxite series in the Longdong area of the Ordos Basin indicates that the bauxite series can not only serve as regional cap rocks， but also as high-quality reservoirs in local areas. Study on the distribution characteristics and variation patterns of elements in bauxite rock series is based on core observation， rock casting thin section identification， combined with geochemical analysis of major， trace， and rare earth elements. The sedimentary environment and element migration characteristics of the Longdong bauxite rock series are discussed. The results show that： （1） The Taiyuan Formation bauxite series in the Longdong area is characterized by high aluminum， low silicon， iron， and titanium content； （2） The overall performance of rare earth elements is relatively enriched， and this is related to the preservation of minerals with strong weathering resistance that contain rare earth elements during the weathering of the parent rock， but there is a significant change in the total amount. Trace elements such as Ni，Co，V，Ga，Hf and Sc exhibit similar variation characteristics，and it indicates that it has good stability during the diagenetic evolution of bauxite rock；（3）The diagenetic environment of the bauxite rock series in the Longdong area has undergone multiple alternations of redox environments，mainly composed of terrestrial freshwater sedimentary environments with transitional and marine characteristics.This achievement can provide reference for further rese-arch on the sedimentary environment and material sources of Taiyuan Formation bauxite in the Longdong area.

The deep shale gas reservoirs in the north Luzhou District of the Sichuan Basin are affected by multiple phases of tectonic movements， and are characterized by complex tectonic conditions， rapid changes in in-situ stress， which leading to the difficulties of in-situ stress prediction. A specific in-situ stress seismic approach based on pre-stack azimuthal anisotropic inversion is proposed. Pre-stack AVAZ inversion approach applied azimuthal anisotropy AVA equation under Bayes theory framework. The elastic and anisotropic parameters of the shale gas reservoir are inverted from pre-stack Offset Vector Tile （OVT） gather. Meanwhile， a formula Differential Horizontal Stress Ratio （DHSR） based on the fracture density and Poisson's ratio representation is derived， which is utilized to estimate the DHSR of shale gas reservoir. Wufeng Formation-Long 1 submember and favorable areas for shale gas exploration and development were delineated. This provides reliable geophysical evidence for reserve evaluation， well trajectory design， and reservoir stimulation in the study area. Using this method， deep shale gas in the Wufeng Formation–Long11 subsection of the northern Luzhou area in the Sichuan Basin was predicted by DHSR， and favorable areas for shale gas exploration and development were delineated. This provides a reliable geophysical basis for the reservoir evaluation， well trajectories designment， and reservoir modification.

Bauxite series strata are well developed in the Ordos Basin. In recent years， significant progress has been achieved in the exploration and development of bauxite gas reservoirs within these strata. A reservoir-forming model has been proposed， emphasizing the role of paleogeomorphology in controlling reservoir formation， the contribution of coal rock in supplying hydrocarbons near the source， and the influence of lithology and structure in reservoir development. This model sheds light on the near-source scale reservoir-forming potential of bauxite. In order to elucidate the influence of paleogeomorphology on bauxite gas reservoir， this study focuses on the Permian Taiyuan Formation in the Longdong area of the Ordos Basin. Using the impression method， the paper reconstructs the paleogeomorphology characteristics of the Pre-Carboniferous Taiyuan Formation. By integrating drilling， logging， seismic， outcrop observation， analysis， and actual production data， the study analyzes the impact of paleogeomorphology on bauxite gas reservoirs in the Taiyuan Formation of the Longdong area. The study reveals that： （1） The Taiyuan Formation exhibits three primary palaeogeomorphology units， namely highland， slope， and depression， along with three secondary micro-palaeogeomorphology units， which include buried pit， terrace， and groove. Specifically， the palaeogeomorphology of the Taiyuan Formation predominantly features karst slopes， with a general trend of higher elevations in the southwest and lower elevations in the northeast. The paleogeomorphology plays a crucial role in controlling the pre-Carboniferous bauxite gas reservoirs in the area by influencing the timing and intensity of supergene leaching. （2） The thickness of bauxite in buried pits and terraces is largely controlled by paleogeomorphology， where dissolved pores and fractures are well developed. （3） Additionally， the distribution of sedimentary facies is influenced by paleogeomorphology， leading to thick bauxite deposits in the margins of ancient land and tidal flat facies. （4） The development of reservoirs is controlled by both paleogeomorphology and micropaleogeomorphology， with bauxite in highlands， buried pits， and terraces exhibiting good physical properties and reservoir quality. Karst slopes present favorable conditions for reservoir formation， enhancing the enrichment of natural gas. The formation mechanism of bauxite gas reservoirs involves hydrocarbons being generated in the upper coal measure source rock， migrating downwards to accumulate in the porous bauxite reservoir during the supergene stage. This process is driven by hydrocarbon generation， with the porous nature of the bauxite being a key geological factor in the formation of natural gas reservoirs.

The scale of the Taiyuan Formation bauxite gas reservoir in the Longdong area of the Ordos Basin is relatively small and scattered， with diverse sedimentary types， variable lithology， and large differences in physical property parameters. The main controlling factors for gas content in the reservoir are unclear， and the gas water relationship is complex， resulting in significant differences in gas testing. From the perspective of logging， this study conducted an in-depth analysis of the relationship between gas testing results of aluminum bearing rock reservoirs and reservoir lithology thickness， physical properties， and electrical properties. It was clarified that the main factors affecting the production of aluminum bearing rock reservoirs are lithology homogeneity， thickness， electrical properties， and physical properties in order of weight. On this basis， a regional gas and water identification chart is established by combining lithology identification and porosity calculation based on lithology. In response to the limitations of the graphical method in the application of aluminum bearing rock reservoirs with poor physical properties， based on the rapid identification method of aluminum bearing rock using acoustic time difference and natural gamma envelope area， an innovative lithology homogeneity index based on envelope area accumulation is established. Furthermore， combined with gas sensitive logging variables such as porosity and resistivity， a quantitative indicator parameter for gas signal enhancement factor and a fluid sensitivity factor are constructed， which can intuitively indicate gas content in aluminum bearing rock reservoirs and achieve effective gas water identification in aluminum bearing rock reservoirs. At the same time， based on rock electrical experiments， saturation calculation models for different types of reservoir spaces were established， and the water saturation that characterizes the gas content of the reservoir was quantitatively calculated. The application of research methods in gas testing and layer selection for new and old wells in bauxite reservoirs has shown significant results， effectively improving the accuracy of logging interpretation and supporting regional single well gas testing and layer selection and gas reservoir understanding.

The largest integrated marine carbonate gas field-Anyue Gas Field in China has been found in the central Sichuan Basin. However， the deep （>4 500 m） carbonate reservoir has low porosity-permeability and extremely strong heterogeneity， which has constrained the large-scale production and development in the deep carbonate reservoirs. For this contribution， the small （vertical displacement <20 m） strike-slip faults interpretation and seismic prediction of the strike-slip fault damage zone are carried out in Anyue Gas Field， and has firstly deployed well drilling on “sweet spot” reservoir （high porosity-permeability reservoir） along the strike-slip fault zones. Based on steerable pyramid reprocessing of 3D seismic data， the small Ⅲ-IV order strike-slip faults can be identified， and the total 1 860 km length of strike-slip faults in Anyue Gas Field have been found and mapped. The symmetric illumination attribute processed by the navigation pyramid was used to characterize the deep dolomite strike-slip fault fracture zone. The area of the strike-slip fault fracture zone was discovered and confirmed to be 1 440 km²， indicating that there is a large-scale fault-controlled “sweet spot” along the weak strike-slip fault zone. Through these data， a new development plan of the deep gas reservoir is proposed from sedimentary microfacies-controlled large-scale reservoir to preferential drilling of fault-controlled “sweet spot” reservoir. In this context， pilot test wells have been firstly deployed in different fault damage zones， and subsequently completed wells have penetrated fracture-vug reservoirs and obtained high gas production more than one times in the deep reservoirs. In the deep carbonate reservoirs， 49 development wells located in the strike-slip fault damage zones had an annual gas production up to 50.4×10⁸ m³ in 2023， which is the first pre-Mesozoic deep strike-slip fault-controlled large gas fields. The development practice in Anyue Gas Field has suggested a tremendous potential of high-yield and high-efficient development of deep strike-slip fault-controlled “sweet spot” reservoirs， and initiated a new exploitation frontier of deep strike-slip fault-controlled gas reservoir in the Sichuan Basin.

With the development of deep and unconventional oil and gas exploration， condensate oil has attracted more and more attention as a high-quality resource. For systematic study the exploration status and the complex formation mechanisms of condensate oil and other key problems， the condensate oil has been analyzed in terms of definition， exploration history， distribution characteristics， origin classification and quantitative analysis. It is pointed out that the proved geological reserves of condensate oil in China are about 710 million tons and there are 163 condensate oil and gas fields （reservoirs）. Condensate gas fields with proven reserves of more than 10 million tons mainly distributed in Tarim Basin and Bohai Bay Basin， which has the characteristics of the coexistence of large condensate gas fields in eastern and western China. On the basis of innovative understanding of primary condensate gas reservoirs， the source-reservoir relationship and other factors are further considered， and the two types of primary and secondary condensate gas reservoirs discovered in China are further divided into two sub-categories： Remote （external） and near （internal）. It also improves the shortcomings of primary condensate gas reservoirs in the aspects of hydrocarbon generation parent material， evolution stage and accumulation mode. According to the established new genetic types， we then reviewed the genetic types and accumulation characteristics of condensate gas reservoirs in China. It is pointed out that no matter in terms of the number of condensate gas reservoirs or proven reserves， China's condensate oil is mainly of primary origin. The primary condensate in China accounts for about 70% of the total proved geological reserves， and the proportion of secondary condensate is about 30%. The proportion of remote （external） accumulation types （about 57%） is higher than that of near （internal） （43%）.

At present， the breakthrough of shale gas exploration in China is mainly concentrated in the medium and shallow overpressured shale gas reservoir. With the deepening of research， shale gas exploration gradually goes to the deep layer. The Baima block of Fuling shale gas field is a deep overpressured gas reservoir with great exploration potential. Based on the well logging data and test analysis data of Wufeng-Longmaxi formations in well J148-1， the gas bearing characteristics and influencing factors of Wufeng-Longmaxi formations are analyzed in this paper， and the formation and enrichment mechanism of shale gas and the accumulation model of shale gas are discussed. The shale gas content of Wufeng-Longmaxi formations ranges from 1.09 to 6.81 m³/t （with an average of 3.15 m³/t）， and increases with increasing depth. The average gas content of small formations 1-3 is 5.35 m³/t， which is a favorable shale gas interval. The total organic matter content， mineral composition， reservoir properties and preservation conditions all have a certain control effect on the gas content of the shale.TOC of the Wufeng-Longmaxi formations is between 1.29% and 5.50%（with an average of 2.75%）， and increases with the increase of burial depth. Quartz content is 17.2%-64.7% （average 36.1%）， feldspar content is 2.7%-14.5% （average 8.0%）， carbonate mineral content is 2.0 %-56.6% （average 12.6%）， pyrite content is 1.4%-6.7% （average 3.4%）. The clay mineral content is 17.2%-54.3% （average 40.1%）. The porosity of 1-4 layers is between 2.38% and 5.64% （average 4.06 %）， the porosity of 8-9 layers is between 1.95 % and 2.75% （average 2.24%）， and the permeability of 1-4 layers is between 0.03×10^-3 and 16.43×10^-3 μm² （average 0.75×10^-3 μm²）. The permeability of 8-9 small layer ranges from 0.05×10^-3 to 55.63×10^-3 μm² （the average is 2.31×10^-3 μm²）， and the total organic matter content， brittle mineral content and porosity are positively correlated with the gas content. There are three types of pores in the shale： inorganic pores， organic pores and micro-fractures， mainly organic pores. The study area is far from the main fault， regional cap layer is developed， top and bottom lithology is dense， preservation conditions are good， free gas is abundant， and the reservoir formation model is broad and slow syncline. The shale of Wufeng-Longmaxi formations in the study area was immature from the end of Ordovician to the Late Silurian， entered the mature stage in the late Silurian， entered the high mature stage in the Middle Jurassic， entered the over-mature stage in the Late Jurassic， and stopped thermal evolution in the Middle Cretaceous.

The study of the causes of overpressure is the basis for stress prediction and the research on hydrocarbon accumulation. The Jurassic overpressure is widely distributed in the Mosuowan uplift， located in the central part of the Junggar Basin， which is closely related to hydrocarbon accumulation， making it an important topic for further research. This study comprehensively utilizes various methods such as log curves combination analysis， Bowers method， velocity-density crossplotting， correlation of porosities， and comprehensive analyses to discuss the causes of overpressure. The research shows that overpressure is generally developed in the Jurassic of Mosuowan uplift， Junggar Basin. The overpressure is mainly located in the deep formation of 4 000-4 500 m， and the pressure coefficient ranges from 0.92 to 2.11， with an average pressure coefficient of 1.33. On the planar scale， the eastern part experiences more significant overpressure， with pressure coefficients of up to 2.1， while the western part has relatively weaker overpressure， with pressure coefficients reaching up to 1.6. Sonic transit time， density， and resistivity log responses show clear indications of overpressure， with varying degrees of reversal. Based on the comprehensive analysis using multiple methods， it is determined that the overpressure in the Jurassic formations of the Mosuowan uplift in the Junggar Basin is mainly influenced by hydrocarbon generation and pressure transmission. The contribution of chemical compaction is slightly higher in the eastern part than in the western part， while the contribution of under compaction is weak or nonexistent.

A significant breakthrough has been made in the Upper Paleozoic play in Dagang area of Huanghua Depression， Bohai Bay Basin over the past four years. This paper aims to analyze the key factors of hydrocarbon accumulation and identify the exploration prospective area. The geological， geochemical， logging and seismic data are allowed to investigate the source rock， reservoir distribution and properties， natural gas charging time and petroleum system model. The results show that the upper Paleozoic coal bedding source rocks have good organic matter with two peak periods of hydrocarbon generation. The reservoir responds low porosity and low permeability clastic rocks， but secondary pores and fractures have developed as a result of subsequent later tectonic movement. The origin source rock， secondary pore reservoir and the activity of faults are the key controlling factors for the gas accumulation. We build a petroleum system model as “two periods of hydrocarbon expulsion， source-sink superimposed， late fault activity reshape prospect， late gas charging”. The gentle high in the deep depression buried hill zone and slope of buried hill will be the promising exploration area. Three favorable target areas for future exploration are proposed： the slope area of Wumaying-Wangguantun sag， Dongguang Dongyi and Qibei.

The explorational breakthroughs have consistently revealed a huge new oil and gas production area in the Bozi-Dabei regions within the western Kelasu structural belt， Kuqa Depression， Tarim Basin. However， oil and gas compositions， physical properties， and oil and gas reservoir types are complex. There are unclear oil and gas phase states and physical property distribution rules， and the main controlling factors of oil and gas phase states are not clear. In this study， 75 production-well data were systematically collected for statistical analysis and phase simulation， including hydrocarbon compositions and physical parameters of oil and gas production （e.g.， density， viscosity， colloidal content， asphaltene content， dryness coefficient， production gas-oil ratio）. Oil and gas reservoirs were divided into four types of volatile oil reservoirs， condensate gas reservoirs， wet gas reservoirs and dry gas reservoirs according to the dryness coefficient and gas-oil ratio， and then the phase characteristics and occurrence of oil and gas were reconstructed under geological conditions to reveal the main controlling geological factors of phase distribution. The results indicate that the hydrocarbon fluids are generally characterized by the distribution of block-divided from east to west and belt-divided from north to south in the study area. The physical parameters （e.g.， density， viscosity etc.） show a gradual increasing trend from west to east. The occurrence of oil and gas transforms from liquid phase to condensate phase， condensate （wet gas） phase and dry gas phase from deep to shallow reservoirs. Four types of oil and gas are located in circle-curved distribution caused by the maturity differences of the Jurassic Qiakemake source rocks. The distribution of target strata controls the distribution of volatile oil reservoirs， condensate gas reservoirs and wet gas reservoirs. The distribution of dry gas reservoirs is attributed to the combined contribution of mature Jurassic and high-over mature Triassic source rocks. This study has successfully confirmed the distribution of oil and gas phases and physical properties， exploring the main controlling factors for the complexity of oil and gas phases in the Bozi-Dabei regions， which can provide theory-supported helps for the further oil and gas exploration and development in the Kuqa Depression.

Based on thin section identification， the organic geochemistry， XRD， combined with scanning electron microscopy， N₂ isothermal adsorption and high pressure mercury injection tests， the characteristics of laminated shale lithofacies were identified and the reservoir pore structure was comprehensively analyzed， and then the favorable shale lithofacies and main controlling factors of pore development were clarified. According to the classification standard of “abundance of organic matter and mineral composition”， the shale of Qingshankou Formation is divided into seven lithofacies： M-L， S-M， M-M， C-M， S-H， M-H and C-H. The kind of C-H shale lithofacies is regarded as the favorable type in the study area， because it has absolute hydrocarbon generation potential， and its reservoir space is well developed with superior pore structure parameters， which is dominated by slit clay mineral intercrystalline pores， intergranular pores and micro-fractures. The shale reservoir space of Qingshankou Formation is controlled by laminae development， TOC content and mineral composition. The felsic lamination effectively alleviates overlying rock compaction， organic acid diffusion and formation of overpressure fractures improve macropore volume ratio， and the clay mineral intercrystalline pores and fractures provide the main specific surface area and pore volume.

Significant breakthroughs have been made in the exploration of bauxite rock gas in the Ordos Basin， but the petrogenesis of bauxite rock is still unclear. One of the key issues is that the provenance of bauxite rock has not been resolved yet. Therefore， this study conducted provenance analysis on the bauxite rock series in the Benxi Formation in the Shenmu-Mizhi area of the eastern Ordos Basin using methods of detrital zircon chronology and stable element geochemistry. The results show that the detrital zircons in the bauxite rock series are angular shaped magmatic zircons， with particle sizes ranging from 0.06 mm to 0.03 mm. The zircon age displays two peaks，which correspond to 500-400 Ma and 350-300 Ma，respectively.The zircons in the overlying clastic rocks of the bauxite rock series are mainly elliptical metamorphic zircons with particle sizes ranging from 0.13 mm to 0.06 mm. About half of the zircon ages are disharmonious. The harmony age peaks of zircon are 2 600-2 300 Ma and 2 100-1 700 Ma. The bauxite rock series are significantly enriched in stable elements. Their Zr/Nb values are similar to those of the underlying carbonate rocks， but are significantly different from the Zr/Nb values from the overlying clastic rocks and the tuffs in the Majiagou Formation in the basin. After comparative analysis， it is believed that the North China Craton basement to the northern basin is the provenance of the overlying clastic rocks， but makes little material contribution to the bauxite rock series. The Lower Paleozoic and Carboniferous tuffs in the basin are the direct sources of detrital zircons in the bauxite rock series， but their material contribution to the bauxite rock series is extremely limited. The main provenance of the bauxite rock series is the Lower Paleozoic carbonate rocks within the Basin.

Hydrogeochemical characteristics of coalbed methane co-produced water have significant implications for the secondary biogenic methane. Understanding the relationship between groundwater and secondary biogenic methane is crucial for natural gas exploration and development. The chemical compositions， hydrogen and oxygen isotopic compositions （ {\mathrm{\delta }}^{\mathrm{18}} {\mathrm{O}}_{{\mathrm{H}}_{\mathrm{2}}\mathrm{O}} and \mathrm{\delta } {\mathrm{D}}_{{\mathrm{H}}_{\mathrm{2}}\mathrm{O}}）， the abundance and isotopic compositions （δ¹³C_DIC and Δ¹⁴C_DIC） of dissolved inorganic carbon （DIC） of fifty-seven CBM co-produced water samples and three river samples from six blocks of Qinshui Basin in China are analyzed in this study. Results show that hydrogen and oxygen isotopes are distributed near the atmospheric precipitation line， suggesting that coalbed methane well-produced water mainly originates from atmospheric precipitation. Sulfate microbial reduction is identified as a crucial factor in the enrichment of deuterium isotopes in the Zhengzhuang and Yangquan blocks. The chemical composition of water produced from coalbed methane wells in the study area is predominantly of Na-HCO₃ type. The evolution of geochemical compositions of coal seam water is controlled by water-rock interaction and cation exchange processes. Stable isotope analysis of water from coalbed methane wells in the six study blocks in the Qinshui Basin shows elevated δ¹³C_DIC values （from -4.19‰ to 34.80‰， average 16.51‰）， and a clear positive correlation with dissolved inorganic carbon content， likely indicating the result of microbial methane production. The negative correlation between δ¹³C_DIC and SO₄ ^2- in coalbed methane produced water， as well as the positive drift in \mathrm{\delta } {\mathrm{D}}_{{\mathrm{H}}_{\mathrm{2}}\mathrm{O}}，suggests the widespread occurrence of secondary biogenic methane in coalbeds with different maturities in the Qinshui Basin. The negative correlation between δ¹³C_DIC and vitrinite reflectance （R _Omax） further indicates the presence of secondary biogenic methane in coal beds with different maturities， particularly in shallowly buried and low maturity coal beds. The integration of geochemistry and microbiology will further elucidate the pathways and mechanisms of secondary biogenic methane formation.

In recent years， China has carried out fruitful exploration and development of medium and shallow shale gas with a burial depth of 700-2 000 m in Zhaotong Shale Gas Demonstration Zone of Sichuan Basin. However， horizontal well technology and large-scale hydraulic fracturing technology adopted in shale gas development have the risk of water environment pollution， especially in the carbonate rock distribution area in southern China， which has complex geological conditions and fragile ecological environment. The study of water environmental pollution risk is particularly important. In this study， the composition of trace elements， anions， cations， and strontium isotopes in the flowback water of Y105 well area with vertical depth <2 500 m in the Taiyang block， Zhaotong area， Sichuan Basin was analyzed and compared with that of Weiyuan， Changning and Fuling shale gas fields. It is pointed out that shale gas fracturing flowback water in Y105 well area of Taiyang shallow layer has the following three characteristics： （1） The flowback water is high in salts and heavy metals. The average contents of K， Na， Ca and Mg were 153 mg/L，7 473 mg/L，162 mg/L， 34 mg/L， respectively， and the average contents of Cl and Br were 10 912 mg/L and 52 mg/L， respectively. The average contents of Li， B， Sr， Ba and Rb were 21.9 mg/L， 14.3 mg/L， 27.8 mg/L， 37.4 mg/L and 0.25 mg/L respectively， which could not be directly discharged. The average Br/Cl ratio is 0.002 1， it is relatively rich in Ca and poor in Mg compared with evaporative seawater， the content of Sr， Ba and Rb is positively correlated with the content of Cl. All of them indicate that the flowback water is the mixture product of the fracturing injected fluid and entrapped brine of the host shale formation. The high salt end of the flowback water has the characteristics of evaporative seawater， but it also experiences water-rock reaction. （2） The ⁸⁷Sr/⁸⁶Sr ratio ranges from 0.716 5 to 0.717 2 （with an average value of 0.716 7）， indicating that there is a strong water-rock interaction between fracturing injected fluid and shale formations with high strontium isotope ratios. Compared with the flowback water in Weiyuan， Changning and Fuling shale gas fields， flowback water in the Taiyang block has relatively low ⁸⁷Sr/⁸⁶Sr ratios， but still much higher than that of surface water and biocides， which is a good identification index. （3） The element composition of the flowback water has a certain correlation with the vertical burial depth of the shale. For example， when the vertical depth of the Y105H3 platform increases from 2 245.16 m to 2 406.16 m， the content of cations， ions， and trace elements has varying degrees of change， and shows a certain change law， which may reflect the influence of temperature， pressure and other factors.

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.

In order to explore the diagenetic characteristics， influence mechanism and the distribution of dominant diagenetic facies of Fengcheng Formation in the southern margin of Mahu Sag， this paper quantitatively characterized the reservoir transformation intensity of compaction， cementation and dissolution on the basis of the analysis of petrological characteristics， pore types， diagenesis and diagenetic environment evolution， and established a diagenetic facies division scheme. Based on the evaluation results of single well coring interval， the characteristics of diagenetic facies distribution are described， and the influencing mechanism of diagenetic facies distribution is explained. The results show that the reservoir space of Fengcheng Formation in the study area is characterized by a dual medium of “matrix-pores dominated and micro-fractures supplemented”， in which the intra/intergranular dissolved pores are dominant in the matrix pores. The Fengcheng Formation has undergone the evolution of alkaline sedimentary environment and alkali-acid-alkaline diagenetic environment. The alkaline sedimentary and early alkaline diagenetic stages are the important periods for the loss of intergranular pore cementation， the hydrolysis of volcanic materials and the formation of solution pore by plagioclase albitization. The reaming in the acidic diagenetic environment in the middle stage makes the dissolution pore become the main reservoir space， and the densification degree is somewhat eased. In the late alkaline diagenetic environment， the concentration of alkaline mineral ions increases again and begins to precipitate in the remaining intergranular pores， solution pores， and other reservoir spaces， and the reservoir densification degree is further improved. The cementation and dissolution of fan delta plain and front junction in the study area were weak， and more compact phases developed， with an average porosity of about 4.9%. From the inner front of the fan delta to the junction of the outer front， the dissolution is stronger than the cementation， and the cementation-dissolution phases are dominant， with an average porosity of about 6.6%， and the dissolution phases with an average porosity of 9% are near the central and southern faults. The outer front of fan delta is mostly developed with solution-cementation facies， and the average porosity of the reservoir is about 3.1%. In general， alkaline diagenesis in the alkaline lake sedimentary setting has a two-sided effect on reservoir reconstruction， and the cementation-dissolution phases and the dissolution phases under the control of acid/alkaline dissolution are favorable places for tight oil accumulation in this area， and are also the key factors for the high productivity in this area.

In the Longdong area of the Ordos Basin， the bauxite section of the Taiyuan Formation has recently been tested to obtain industrial gas flow， which breaks the traditional understanding that the bauxite of the Taiyuan Formation is the caprock of the Lower Palaeozoic Ordovician weathered crust， indicating that bauxite gas is an undiscovered unconventional natural gas reservoir. In order to find favorable facies and expand the discovery of gas reservoirs， this paper compares the core and logging analysis data to clarify that coal seams， carbonaceous mudstones， conventional mudstones and aluminum-bearing rock formations are developed from top to bottom in the Taiyuan Formation of Ordos Basin， among which the typical aluminum-bearing rocks have the characteristics of “three highs and two lows” of high gamma， high neutron， high uranium， low sonic wave and low potassium. According to the difference in the content of the main constituent mineral diasporite monohydrate of aluminite， the aluminite was subdivided into three types of rocks： bauxite， argillaceous bauxite and bauxite mudstone. Combined with core， rock thin section， scanning electron microscope and imaging logging data， the aluminites were divided into six lithofacies： layered/striated argillaceous bauxite facies， massive， layered， soybean oolitic bauxite facies and weakly layered and clastic bauxite mudstone facies. Comparing the nuclear magnetic resonance and production test data， it is clear that the layered bauxite lithofacies and soybean oolitic bauxite facies have a large number of intragranular dissolution pores， which are favorable lithofacies for oil and gas accumulation. This paper deepens the understanding of the lithofacies imaging characteristics and favorable reservoirs of the Permian Taiyuan Formation in the Ordos Basin， which is of guiding significance for the exploration and development of new bauxite natural gas reservoirs in the Taiyuan Formation in the southwest of the basin and the Benxi Formation in the eastern part of the basin.

Previous researches analyzed the genesis mechanism of bauxite in the Taiyuan Formation in Longdong area of Ordos Basin by using core and logging data， and believed that karstification controlled bauxite enrichment， and bauxite developed in gully areas. Previous research on seismic prediction methods for bauxite reservoirs has not been systematic enough. It is urgent to apply three-dimensional seismic data to characterize ancient landforms and predict the development areas of bauxite reservoirs. Aiming at these issues， this paper analyzed seismic forward modeling and combined existing geological understandings to explore the seismic prediction method of Taiyuan Formation bauxite and favorable zones selection in Longdong area. The study obtained the following understandings： （1） The thickness between the bottom of Shihezi Formation and the bottom of Taiyuan Formation correlates well with the thickness of Taiyuan Formation， which can be used to predict macro paleo-geomorphology. Based on the prediction of macro paleo-geomorphology， the micro paleo-geomorphology was restored through “trend surface method”， and further divided into main gullies， minor gullies， hidden pits and other “negative landforms” within each unit， refining the micro paleo-geomorphology. （2） Under the premise of suppressing strong reflections from coal seams， the P-wave impedance obtained through inversion of post-stack geological statistics can well predict the spatial distribution of bauxite in Longdong area. （3） Comprehensively predicting the Taiyuan Formation bauxite reservoirs in Longdong area using factors like paleo-geomorphology， lithology， faults and structures formed a “one low， one weak， one high and two zones” well location selection mode， which played a positive role in efficient deployment of bauxite wells. The high-yield gas flow obtained from the gas testing of the Taiyuan Formation bauxite rock in Well L47 marks a significant breakthrough in the new field of bauxite rock in the basin. Currently， a favorable exploration area of nearly 8 000 square kilometers has been confirmed， with broad exploration prospects.

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.

The Xujiahe Formation of the Upper Triassic in the Sichuan Basin was a key layer for the exploration and development of tight sandstone gas in China. The Xujiahe Formation was divided into T₃ x ¹ to T₃ x ⁶ from bottom to top， among which T₃ x ¹， T₃ x ³， and T₃ x ⁵ were the main layers of hydrocarbon source rock development. Regarding this source rock， previous research had mainly focused on geochemical analysis， with few reports on semi-quantitative analysis of organic matters in the source rock， making it difficult to accurately evaluate the hydrocarbon generation potential of source rocks with different geological backgrounds in the basin. This study selected 406 field profiles and drilling samples from the central and western regions of the Sichuan Basin. Based on organic petrology and carbon sulfur analysis， combined with organic geochemical and carbon isotope characteristics analysis， the study revealed the coupling relationship between sedimentary environment and organic matter enrichment in different layers of the Xujiahe Formation. The overall organic matter abundance of the Xujiahe Formation source rocks was high （TOC=4.09%）， with organic matter types II₁ to III （hydrocarbon generating biological sources include planktonic algae， higher plants， and animal debris） and R _O=0.70%-1.23%， making them good to high-quality source rocks. Among them， there were significant differences in the source rocks of the T₃ x ¹， T₃ x ³， and T₃ x ⁵， mainly reflected in： （1） The bio-precursors of hydrocarbon in the T₃ x ¹ from the Jiange area of Guangyuan were mainly higher plants， with the exinite group accounting for 15.38%； the Shifang area was affected by marine transgression， with algae and higher plants as the main bio-precursors of hydrocarbon， and low organic matter carbon isotopes in the samples（δ¹³C=-25.51‰）. （2） The T₃ x ³ was mainly composed of sandy mudstone and TOC=4.04%， while the bio-precursors of hydrocarbon were mainly composed of higher plants， accounting for 47.78%. （3） The maturity of the T₃ x ⁵ was relatively low （R _O=0.96%）， and the content of layered algae formed by the degradation of lower aquatic organisms in organic matter was relatively high， up to 44.93%， making it a good source rock for oil generation. This study compared the organic petrology and geochemical characteristics between different layers of the Xujiahe Formation， hoping to provide basic data and certain references for the exploration and development of oil and gas in the Xujiahe Formation in the Sichuan Basin.

The Qijiang area on the southeastern edge of the Sichuan Basin has developed thrust fold belts since the Jurassic， but there is a lack of systematic research on multiple types of fault systems and their control over oil and gas since the deep Paleozoic. Based on the drilling and high-precision 3D seismic data， the identification of faults in Qijiang area and its adjacent areas is carried out according to the high-precision coherence and other geophysical properties. The profile shape and plane distribution are characterized， and the differences in the formation and evolution process of different faults and their control over the formation and preservation of oil and gas reservoirs are clarified. The research results indicate that the Qijiang area mainly develops two types of faults： thrust and strike slip. The profile is characterized by multiple sets of detachment layers with layered fracture characteristics. The plane mainly develops three sets of faults in the NNW-SSE， NE-SW， and near W-E directions. The NNW-SSE trending fault is a longitudinal overlap of the Lower Paleozoic strike slip fault during the Caledonian period and the Upper Paleozoic Mesozoic thrust fault during the Yanshan period； The NE-SW trending fault is a reverse thrust of the Hercynian ring-shaped normal fault during the Yanshanian period； The nearly W-E trending fault is a reverse fault formed during the Xishan period by the orogenic compression in the direction of Daluoshan on the southern edge of the basin. The development of karst reservoirs in the Maokou Formation was controlled by NNW-SSE trending strike slip faults and NE-SW trending normal faults under the tension background of the Haixi period； Under the compression background of the Yanshan period， the activation of faults formed structural fractures and connected the source and reservoir， and the overlapping of source faults and large-scale reservoirs is a key area for the exploration of Permian oil and gas in the Qijiang area； The strength of the strike slip effect of the NNW-SSE trending fault since the Xishan period controls the later stable preservation conditions of shale gas in the Silurian Longmaxi Formation.

The mid-deep CBM has the characteristics of high gas content， high saturation， and contains free gas. New well seismic calibration and multi-attribute joint tectonic interpretation techniques are adopted to finely understand the tectonics， calibrate the interpreted layers， and accurately identify the faults and trapped columns. The unit water influx in An13 reservoir area of Anze block of the west wing of southern Qinshui Basin is below 4 m³/（m·d） in the area， and the main body is below 1 m³/（m·d）， with weak hydrodynamic conditions. The statistical results of the coring data of the evaluation wells show that： （1） The cracks in the study area are relatively developed， the west is more developed than the east， the anisotropy is stronger at each point in the crack development area， the cracks in the direction of near north-south and near east-west are relatively developed， which belongs to the stress mechanism of the strike-slip faults， and the direction of the maximum horizontal principal stress NNE is favorable for the extension of fracturing cracks. （2） The porosity of the 3^# coal seam averages 4.48%-4.5%. In the process of tectonic folding， due to the uplift of strata in the dorsal part， the pressure of strata decreases， methane is transported from the low part of the tectonics to the high part of the tectonics through the channels of pore space and fissure， etc.， and the water of the coal seam seeps from the high to the low part of the tectonics due to the effect of gravity， and the coal seam gas enrichment mode of “the top of the tectonics is rich in gas and poor in water， the waist gas and water coexist， the bottom of the gas rich in water and poor in gas” is formed step by step. In order to obtain high gas production， it is necessary to find a favorable area in the reservoir where the gas saturation of the coal bed is more than 70% and the gas content is more than 14 m³/t. （3） For the open system of the reservoir with external water recharge， the supply boundary pressure remains unchanged， and the pressure within the drainage range decreases slowly due to external water recharge； when the reservoir is a closed system， the water body of the reservoir is of the stagnant type； when the reservoir is a semi-closed system， the water body of the reservoir is of the weak runoff type. （4） Coalbed methane wells in the Mabidong block of the west wing of southern Qinshui Basin are generally buried at a depth of 800-1 200 m， with an average fracturing fluid volume of 946.5 m³. The single-phase flow period after returning to the drainage adopts a fixed water production volume and a fixed flow pressure rate， and the single-phase flow pressure drop rate is kept at 0.05-0.1 MPa/d， with the average time of the single-phase period of 108 days， the cumulative drainage volume of 560 m³， and an average desorption pressure of 4 MPa， and the drainage curve is of the rising water production type， with a sharp peak before desorption and a long stable production period.

《天然气地球科学》2024年度审稿专家名单

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.

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.

In view of the key geological problems to be solved in the exploration of unconventional natural gas in Ordos Basin， the dynamic process and relationship between reservoir diagenetic densification and hydrocarbon charging are revealed. The differences of diagenesis types and characteristics of different types of rock facies are carefully compared by combining cast thin section observation， X-ray diffraction and SEM analysis. Through fluid inclusion petrography， microthermometry and laser Raman probe testing， combined with single well burial history and thermal history simulation， the hydrocarbon charging period and age were determined. The diagenesis-hydrocarbon charging evolution sequence of gas-bearing reservoir is established by comprehensively using the observation of the structural relationship between diagenetic minerals and hydrocarbons under the microscope. The results show that there are mainly two periods of hydrocarbon charging in the first member of the Shanxi Formation， i.e.， the first period occurred in the Late Triassic （T₃） to Early and Middle Jurassic（J_1-2） between 220 Ma and 170 Ma， and the second period occurred in the Late Jurassic（J₃） and Early Cretaceous（K₁） between 160 Ma and 100 Ma. The diagenesis， densification process and hydrocarbon charging sequence of different types of rocks are obviously different. The quartz-rich and low-plastic lithic sandstone has good physical properties before hydrocarbon charging in the second stage， and the hydrocarbon charging in the middle diagenesis stage is dense while forming reservoirs. The early diagenetic stage of the plastic-rich lithic sandstone has been basically compacted， while the carbonate dense cemented sandstone due to the occurrence of calcite and siderite， the reservoir densification prevented the entry of the second stage hydrocarbon. In-depth understanding of the relationship between differential diagenesis and hydrocarbon charging in tight reservoirs is of great practical significance for screening favorable areas for natural gas.