Drilling for karst hydrothermal resources in eastern China has posed challenges,including disparities between the temperature and yield of geothermal water.It is evident that relying solely on geothermal anomalies or ...Drilling for karst hydrothermal resources in eastern China has posed challenges,including disparities between the temperature and yield of geothermal water.It is evident that relying solely on geothermal anomalies or indications of karst reservoirs is inadequate for the exploration of karst hydrothermal resources.This study seeks to elucidate the cause of geothermal sweet spots by analyzing the interplay between geothermal anomalies and karst reservoirs and the underlying geological conditions for karst hydrothermal enrichment.Key findings include:(1)the Bohai Bay Basin has been geologically favorable for the development of karst hydrothermal resources since the Mesozoic era;(2)the karst hydrothermal enrichment varies significantly between the basin’s margin and its interior.On the basin margin,the enrichment is largely driven by groundwater activity and faults,particularly where faults facilitate the upwelling of geothermal water.In contrast,within the basin’s interior,karst hydrothermal resources are predominantly influenced by buried hills and are especially enriched in areas facilitating the discharge of deep geothermal waters.展开更多
Soil erosion is a prominent environmental problem in karst regions.Exploring the spatiotemporal variability of soil erosion and the factors that influence soil erosion is of great significance for regional soil erosio...Soil erosion is a prominent environmental problem in karst regions.Exploring the spatiotemporal variability of soil erosion and the factors that influence soil erosion is of great significance for regional soil erosion prevention and control.However,the mechanisms influencing the characteristic features of the karst basins,such as bedrock exposure and lithology,still need to be further explored.This study used GIS technology,the Revised Universal Soil Loss Equation model,Getis–Ord Gi*,and partial least squares regression(PLSR)to identify the dominant factors influencing soil erosion and the spatiotemporal variability of soil erosion in 31 sub-basins of the Dabang River Basin(DRB),a typical karst area of Southwest China,from 2010 to 2020.The results indicated that soil erosion in the DRB from 2010 to 2020 was generally decreasing,the mean soil erosion in the DRB in 2010,2015 and 2020 was 18.46,16.51 and 15.29 t ha^(-1)a^(-1),respectively.During the study period,the area of slight erosion increased by 26.39%(706.54 km^(2)),while severe erosion enlarged by 26.36 km^(2).Spatially,the DRB was primarily affected by medium and slight soil erosion.The hot spot areas of soil erosion(key control areas)were mainly concentrated in the central and southern parts of the basin,decreasing each year,and the area of soil erosion hot pots has decreased from 43.22%to 20.60%.PLSR decoupling results show that elevation,bedrock exposure,land use type,interbedded limestone and clastic rock,and vegetation coverage were identified as the key variables affecting soil erosion,explaining 52.8%of soil erosion variability,with a high value of the Variable Importance on Projection(VIP)more than 1.These results can be used as a reference for comprehensive control of soil erosion and water loss in the basin.展开更多
Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift ...Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift normal fault through detailed seismic interpretation and fault modeling.A total of 289 post-rift normal faults were identified in the study area and can be classified into four types:(1)isolated normal faults above the carbonate platform;(2)isolated normal faults cutting through the carbonate platform;(3)conjugate normal faults,and(4)connecting normal faults.Throw distribution analysis on the fault planes show that the vertical throw profiles of most normal fault exhibit flat-topped profiles.Isolated normal faults above the carbonate platform exhibit roughly concentric ellipses with maximum throw zones in the central section whereas the normal faults cutting through the carbonate platform miss the lowermost section due to the chaotic seismic reflections in the interior of the carbonate platform.The vertical throws of conjugate normal faults anomalously decrease toward their intersection region on the fault plane whereas the connecting normal faults present two maximum throw zones in the central section of the fault plane.According to the symmetric elliptical distribution model of fault throw,an estimation was made indicating that normal faults cutting through the carbonate platform extended downward between-1308 s and-1780 s(two-way travel time)in depth and may not penetrate the entire Liuhua carbonate platform.Moreover,it is observed that the distribution of karst caves on the top of the carbonate platform disaccord with those of hydrocarbon reservoirs and the post-rift normal faults cutting through the carbonate platform in the study area.We propose that these karst caves formed most probably by corrosive fluids derived from magmatic activities during the Dongsha event,rather than pore waters or hydrocarbons.展开更多
The growth of society and population has led to a range of water pollution issues.Among these,non-point source pollution assessment and treatment pose a particular challenge due to its formation mechanism.This has bec...The growth of society and population has led to a range of water pollution issues.Among these,non-point source pollution assessment and treatment pose a particular challenge due to its formation mechanism.This has become a focal point and challenge in water pollution treatment research.The study area for this research was the Huanghou basin in Guizhou Province,southwest China.The land use type of the basin was analyzed using remote sensing technology,and water quality data was collected by distributing points throughout the basin,based on source-sink landscape theory.The distribution map of the basin’s source-sink landscape and the results of water quality data accurately and efficiently identified the areas with high risk of non-point source pollution in the western and southwestern residential and agricultural areas of the upper basin.Hence,a strategy of“increasing sinks and decreasing sources”was proposed.The strategy was implemented at both macro and micro levels to address non-point source pollution in the basin using ecological remediation techniques.The work to control karst rocky desertification should continue at a macro level.The rocky desertification area in the basin should gradually transform into grassland and forested land,while increasing the overall area of the sink landscape.Ecological restoration techniques,such as slope planting,riparian zone vegetation restoration,increasing plant abundance,and restoring aquatic plants,can effectively control non-point source pollution at the micro level.Compared to traditional control methods,this remediation strategy focuses on source and process control.It is more effective and does not require large-scale water pollution control projects,which can save a lot of environmental control funds and management costs.Therefore,it has greater research significance and application value.展开更多
Carbonate karst reservoir is the emphases of Tarim＇s carbonate exploration. However, it is buried at a large depth, which results in Weak seismic reflection signal and low S/N ratio. In addition, the karst reservoir ...Carbonate karst reservoir is the emphases of Tarim＇s carbonate exploration. However, it is buried at a large depth, which results in Weak seismic reflection signal and low S/N ratio. In addition, the karst reservoir contains great heterogeneity, so reservoir prediction is very difficult. Through many years of research and exploration, we have established a suite of comprehensive evaluation technology for carbonate karst reservoir using geophysical characteristics and a geological concept model, including a technique for reconstructing the paleogeomorphology of buried hills based on a sequence framework, seismic description of the karst reservoir, and strain variant analysis for fracture estimation. The evaluation technology has been successfully applied in the Tabei and Tazhong areas, and commercial production of oil and gas has been achieved. We show the application of this technology in the Lunguxi area in North Tarim in this paper.展开更多
Accurate assessment of soil loss caused by rainfall is essential for natural and agricultural resources management. Soil erosion directly affects the environment and human sustainability. In this work, the empirical a...Accurate assessment of soil loss caused by rainfall is essential for natural and agricultural resources management. Soil erosion directly affects the environment and human sustainability. In this work, the empirical and contemporary model of revised universal soil loss equation （RUSLE） was applied for simulating the soil erosion rate in a karst catchment using remote sensing data and geographical information systems. A scheme of alterative sub-models was adopted to calculate the rainfall erosivity （R）, soil erodibility （K）, slope length and steepness （LS）, cover management （C） and conservation practice （P） factors in the geographic information system （GIS） environment. A map showing the potential of soil erosion rate was produced by the RUSLE and it indicated the severe soil erosion in the study area. Six classes of erosion rate are distinguished from the map： 1） minimal, 2） low, 3） medium, 4） high, 5） very high, and 6） extremely high. The RUSLE gave a mean annual erosion rate of 30.24 Mg ha-1 yr-1 from the 1980s to 2000s. The mean annual erosion rate obtained using RUSLE is consistent with the result of previous research based on in situ measurement from 1980 to 2009. The high performance of the RUSLE model indicates the reliability of the sub-models and possibility of applying the RUSLE on quantitative estimation. The result of the RUSLE model is sensitive to the slope steepness, slope length, vegetation factors and digital elevation model （DEM） resolution. The study suggests that attention should be given to the topographic factors and DEM resolution when applying the RUSLE on quantitative estimation of soil loss.展开更多
The influence of land use and land cover on ecological environment is a focus of global change research. The paper chooses an industrial city-Shuicheng in Guizhou Province-as a study area because the karst water quali...The influence of land use and land cover on ecological environment is a focus of global change research. The paper chooses an industrial city-Shuicheng in Guizhou Province-as a study area because the karst water quality around the city is deteriorating with land use and land cover change. The natural susceptibility of karst water system is an important factor leading to karst water pollution. But land use and land cover change is also a main factor according to the chemical analysis of karst water quality and land use change. So it is a good way to protect karst water through rational planning and managing of land use and land cover.展开更多
Based on a large number of drilling,logging,seismic and production data,the differential structures of karst zone and hydrocarbon distribution in different paleogeomorphic units of the Tahe area,Tarim Basin,are discus...Based on a large number of drilling,logging,seismic and production data,the differential structures of karst zone and hydrocarbon distribution in different paleogeomorphic units of the Tahe area,Tarim Basin,are discussed by analyzing the karst drainages and flowing channels.The karst paleogeomorphy of Ordovician in Tahe area is composed of watershed,karst valley and karst basin.The watershed has epikarst zone of 57.8 m thick on average and vadose karst zone of 115.2 m thick on average with dense faults,fractures and medium-small fracture-caves,and 76.5%of wells in this area have cumulative production of more than 5×10^(4) t per well.The karst valleys have epikarst zone,vadose karst zone and runoff karst zone,with an average thickness of 14.6,26.4 and 132.6 m respectively.In the runoff karst zone,the caves of subsurface river are mostly filled by fine sediment,with a filling rate up to 86.8%,and 84.9%of wells in this area have cumulative production of less than 2×10^(4) t per well.The karst basin has no karst zone,but only fault-karst reservoirs in local fault zones,which are up to 600 m thick and closely developed within 1 km around faults.Different karst landforms have different water flowing pattern,forming different karst zone structures and resulting in differential distribution of oil and gas.The watershed has been on the direction of oil and gas migration,so medium-small sized connected fracture-caves in this area have high filling degree of oil and gas,and most wells in this area have high production.Most caves in subsurface river are filled due to strong sedimentation and transportation of the river,so the subsurface river sediment has low hydrocarbon abundance and more low production oil wells.The faults linking source rock are not only the water channels but also the oil-gas migration pathways,where the karst fractures and caves provide huge reservoir space for oil and gas accumulation.展开更多
Objective Complex geological factors have been constraining the oil and gas exploration in the Paleozoic strata of the Qaidam Basin,although there are high-quality hydrocarbon source rocks.One of the most important re...Objective Complex geological factors have been constraining the oil and gas exploration in the Paleozoic strata of the Qaidam Basin,although there are high-quality hydrocarbon source rocks.One of the most important reasons may be reservoir densification due to the multiple stages of destructive cementation,which has hindered our understanding of the Paleozoic petroleum enrichment rules in the Qaidam basin.In recent years.展开更多
To further ascertain the origin of the Ordovician Majiagou Formation reservoirs in the Ordos Basin,the M54-M51 sub-members of the Ordovician Majiagou Formation in the eastern Sulige gasfield of Ordos Basin were taken ...To further ascertain the origin of the Ordovician Majiagou Formation reservoirs in the Ordos Basin,the M54-M51 sub-members of the Ordovician Majiagou Formation in the eastern Sulige gasfield of Ordos Basin were taken as examples to analyze the vertical development characteristics of eogenetic karst and to discover the dissolution mechanism and its control on reservoirs through observation of a large number of cores and thin sections.According to detailed analysis of petrologic characteristics,the reservoir rock types include micritic dolomite,grain dolomite and microbialite which have mainly moldic pore,intergranular(dissolved)pore,and(dissolved)residual framework pore as main reservoir space respectively.The study area developed upward-shallowing sequences,with an exposure surface at the top of a single upward-shallowing sequence.The karst systems under the exposure surface had typical exposure characteristics of early dissolution and filling,indicating these reservoirs were related to the facies-controlled eogenetic karstification.With the increase of karstification intensity,the reservoirs became worse in physical properties.展开更多
The reservoir space,types and distribution characteristics of karst carbonate gas reservoirs in the fourth member of Sinian Dengying Formation(Deng 4 Member)in central Sichuan Basin are analyzed based on the drilling,...The reservoir space,types and distribution characteristics of karst carbonate gas reservoirs in the fourth member of Sinian Dengying Formation(Deng 4 Member)in central Sichuan Basin are analyzed based on the drilling,logging and seismic data.A development model of karst reservoirs is constructed to support the high-efficiency development of gas pools.The research shows that the reservoirs in Deng 4 Member have mainly small-scale karst vugs and fractures as storage space,and can be divided into three types,fracture-vug,pore-vug and pore types.The development patterns of the karst reservoirs are determined.On the plane,the karst layers increase from 65 m to 170 m in thickness from the karst platform to the karst slope,and the high-quality reservoirs increase from 25.0 m to 42.2 m in thickness;vertically,the reservoirs at the top of Deng 4 Member appear in multiple layers,and show along-bedding and along fracture dissolution characteristics.The reservoirs at the bottom are characterized by the dissolution parallel to the water level during the karstification period,and have 3-5 large-scale fracture-cave systems.Based on the reservoir development characteristics and the genetic mechanism,three types of reservoir development models of karst reservoir are established,i.e.,bed-dissolved body,fracture-dissolved body and paleohorizon-dissolved body.The construction of karst reservoir development models and seismic response characteristics of the three types of reservoirs can provide parameter for well placement and trajectory design,and substantially improve productivity and development indices of individual wells and gas reservoirs.The designed production capacity of the gas reservoir has enhanced from the initial 3.6 billion to 6 billion cubic meters,making the profit of the reservoir development increase noticeably.展开更多
Based on the analysis of the responses of conventional logs such as natural gamma(GR), density(DEN), acoustic interval transit time(AC), compensated neutron(CNL), dual lateral resistivity(Rlld, Rlls), and caliper log(...Based on the analysis of the responses of conventional logs such as natural gamma(GR), density(DEN), acoustic interval transit time(AC), compensated neutron(CNL), dual lateral resistivity(Rlld, Rlls), and caliper log(CAL), combined with drilling data,cores, thin section and productivity of 65 wells, the reservoirs in the Mid-Permian Maokou Formation of southern Sichuan Basin were divided into four types, fractured-vuggy, pore-vuggy, fractured and fractured-cavity. The main reservoirs in high productivity wells are fractured-vuggy and pore-vuggy. The reservoirs of Maokou Formation are generally thin, and can be divided into the upper reservoir segment(layer a of the second member to the third member of Maokou Formation, P_2 m^2 a-P_2 m^3) and the lower segment(layer b of the second member of Maokou Formation, P_2 m^2 b). The two reservoir segments are mainly controlled by two grain beaches during the sedimentation of P_2 m^2 a-P_2 m^3 and P_2 m^2 b, the vertical zonation of karst, and the fractures. The upper reservoir segment is generally better than the lower one in development degree and single well productivity, and is much thicker than the lower one. It is thicker in the Yibin-Zigong-Weiyuan-Dazu area, the southwestern area of Chongqing and the southeastern area of Luzhou, while the lower segment is thicker in the Neijiang-Zigong-Luzhou area and the Dazu-Luzhou area. The areas with big reservoir thickness at tectonic slope or syncline parts are the favorable exploration areas.展开更多
Based on outcrop, drilling, logging, geochemical analysis and seismic data, the karst landform and distribution of Permian volcanic rocks at the end of the sedimentary period of the Maokou Formation in the western Sic...Based on outcrop, drilling, logging, geochemical analysis and seismic data, the karst landform and distribution of Permian volcanic rocks at the end of the sedimentary period of the Maokou Formation in the western Sichuan Basin are examined, and their petroleum geological significance is discussed. Affected by normal faults formed in the early magmatic activities and extension tectonic background in the late sedimentary period of the Maokou Formation, a local karst shallow depression under the background of karst slope came up in the Jianyang area of the western Sichuan Basin, where the residual thickness of the Maokou Formation was thinner. Basic volcanic rocks like pyroclastic rock of eruptive facies, basalt of overflow facies, diabase porphyrite of intrusive facies and sedimentary tuff of volcanic sedimentary facies were formed after karstification. However, under the effects of faulting and karst paleogeomorphology, the volcanic rocks in different areas had different accumulation features. In the Jianyang area, with long eruption time, the volcanic rocks were thick and complex in lithology, and accumulated in the karst depressions. In the Zhongjiang-Santai area located in the karst slope, there’s no fault developed, only thin layers of basalt and sedimentary tuff turned up. The karst landform controls the build-up of thick explosive facies volcanic rocks and also the development of karst reservoirs in the Maokou Formation, and the western Sichuan area has oil and gas exploration potential in volcanic rocks and the Maokou Formation.展开更多
The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of...The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of existing data,combined with the characteristics of supplement,runoff and draining of regional karst groundwater,the Visual Modelflow software was used to build a numerical simulation model of Sangu spring Basin.The amount of karst groundwater resource and groundwater environment of the Basin were evaluated under different exploitation schemes,and the changes of karst groundwater environment in the future ten years were also predicted.The fitting error which is less than 0.5 m between the calculated value and measured value of the water level in the fitted borehole accounts for 93%.For the lithologically and structurally complex Sangu Spring Basin,the fitting effect of numerical simulation model was ideal.On the basis of the current mining amount of 111.80 million m3/a,the total redistributed exploited amount in the spring region was 61.79 million m3/a.Under the condition that the quantity of recoverable resources reached 173.59 million m3/a and under different precipitation schemes,all constraint conditions were satisfied,such as regional water level drawdown,maximum allowable water level drawdown in every simulated water source area and the flow rate of Guobi Spring.The results will provide a scientific basis for the rational development and utilization of karst groundwater in Sangu Spring Basin.展开更多
Objective Oil and gas are abundant in the Ordovician Yingshan Formation carbonate karst reservoirs on the northern slope of Tazhong uplift in the Tarim Basin, and have extremely complicated oil-gas-water distribution...Objective Oil and gas are abundant in the Ordovician Yingshan Formation carbonate karst reservoirs on the northern slope of Tazhong uplift in the Tarim Basin, and have extremely complicated oil-gas-water distribution, however. The difference in burial depth of the reservoirs between east and west sides is up to 1000 m. Water-bearing formations exist between oil- and gas-bearing formations vertically and water-producing wells are drilled between oil- and gas-producing wells. Macroscopically, oil and gas occur at low positions, while water occurs at high positiona on the northern slope of Tazhong uplift. The mechanism of differential hydrocarbon enrichment in heterogeneous reservoirs is by far not clarified, which has affected the efficient exploration and development of oil and gas fields in this area.展开更多
In karst area water deficit is one of the main factors constraining sustainable economic development. In 1979 the comprehensive karstic observational field station was set up in Houzhai drainage basin located,\ in Pud...In karst area water deficit is one of the main factors constraining sustainable economic development. In 1979 the comprehensive karstic observational field station was set up in Houzhai drainage basin located,\ in Puding county of Guizhou Province, which can represent most of the small karst drainage basins on the dividing line of the Guizhou Plateau. Geomorphology, water resources and water chemistry were investigated and observed. Based on comparisons of water supply with water demand and analysis of the main problems in water exploitation and utilization. it is found out that the water deficiency was not directly caused by the scarcity of natural water resources. The true reason is the insufficient capacity of water supply caused by the dismatch of the water and soil water resources which can be dealt with by building more irrigation works. Some solutions such as to build scientific basis for water exploitation and utilization and sustainable economic development in karst drainage basins on dividing line of the Guizhou Plateau.展开更多
Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regiona...Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.展开更多
In the Qaidam basin,Northwest China,karstic fissures and caves are developed in many places of the Lower Carboniferous Chengqianggou Fm.and Huaitoutala Fm.and the Upper Carboniferous Keluke Fm.,in which are found typi...In the Qaidam basin,Northwest China,karstic fissures and caves are developed in many places of the Lower Carboniferous Chengqianggou Fm.and Huaitoutala Fm.and the Upper Carboniferous Keluke Fm.,in which are found typical karstic marks.Several suites of transgressive carbonate rocks formed during the Late Paleozoic epoch are preserved as reservoir properties in the Qaidam basin,with paleokarst-related cave-fractured diagenetic structures,which provided the basis for cavefractured development.Carbonate and clastic samples covering or infilling caves and fractures in Carboniferous strata were collected in the eastern Qaidam basin to focus on petrological and geochemical analyses of karst and infilling materials.Based on this study of the Caledonian diagenetic sequence,and bitumen-infilled inclusion temperature and burial history,there existed a continuous atmospheric freshwater leaching process,which played a critical role in the construction of the Carboniferous supergene paleokarsts.Investigation and survey of the tectonic setting,plate paleolatitude and river development intensity also proves that there was abundant rainfall during the Indosinian period,after which the strata undergo a shallow burial process.Because Indosinian period is earlier than the key timing of hydrocarbon-generation of the Carboniferous source rocks,this kind of karst reservoir has potential significance for oil-gas resources in this area.展开更多
In Karst drainage basins, there are the ground water and underground water exchanging frequently, and the shortage of water resources due to having the special double aquifer mediums and unique surface and subsurface ...In Karst drainage basins, there are the ground water and underground water exchanging frequently, and the shortage of water resources due to having the special double aquifer mediums and unique surface and subsurface river systematic structure. This paper is to select 20 research sampling areas coming fromGuizhouProvince, and according to the spectral characteristics of the catchment water-holding mediums and vegetations, and using the remote sensing technique, extract the watershed vegetation index. According to the principle of principal component analysis, using the software of Spss and Matlab is to analyze the impacts of watershed vegetation type on the catchment water-holding ability, and establish the principal component analysis function. Studies have shown that: 1) the watershed vegetation coverage rate plays an important role in Karst basin water-holding ability;2) the catchment water-holding ability is the comprehensive reflection and manifestation of the Catchment Water-storing Capacity (CWC);3) it is much better effects and higher accuracy to monitor/forecast the catchment water-holding volume by using the vegetation indices.展开更多
Based on a large number of geological and geophysical data,the formation,fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area,Tarim Basin,are discussed by a...Based on a large number of geological and geophysical data,the formation,fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area,Tarim Basin,are discussed by analyzing faults and strata thickness.The hoodoo-upland was made of high peaks and narrow valleys in the Ordovician karst slope during the Early Hercynian karst period,which were distributed along the NNE positive flower structure and had inherited evolution.The fault-fractures and fracture-vugs complex were extremely developed,with a thickness of 100 m.The cumulative oil production of 60% oil wells was more than 20×10^(4) t per well in the hoodoo-upland,where the residual thickness of the Ordovician Yingshan Formation was greater than karst depressions.Caves formed by the shelter of collapsed breccias were developed in the valleys.They were 1.6 to 13.5 m high,with a filling rate of 51.6%.The positive flower structure under the settings of strike-slip compression controlled the early formation of the hoodoo-upland on the karst slope,resulting in the differences of drainage distribution and karstification.Compared with the water-rich karst valley,the hoodoo-upland with lean water suffered weaker karstification,had thicker residual stratum,and was higher in terrain.In rainy season,the meteoric water flew and corrode along the cracks,forming a complex network of fractures and caves.Combined with inherited uplift and the effective match of the NNE deep faults,oil and gas continuously charged into the reservoir space in the upland,forming the hoodoo fracture-cave reservoir with vertically quasi continuous distribution,high hydrocarbon abundance and high production.展开更多
基金financially supported by a project of the Ministry of Science and Technology,SINOPEC(No.P13071)a project of the Petroleum Exploration and Production Research Institute,SINOPEC(No.YK514003).
文摘Drilling for karst hydrothermal resources in eastern China has posed challenges,including disparities between the temperature and yield of geothermal water.It is evident that relying solely on geothermal anomalies or indications of karst reservoirs is inadequate for the exploration of karst hydrothermal resources.This study seeks to elucidate the cause of geothermal sweet spots by analyzing the interplay between geothermal anomalies and karst reservoirs and the underlying geological conditions for karst hydrothermal enrichment.Key findings include:(1)the Bohai Bay Basin has been geologically favorable for the development of karst hydrothermal resources since the Mesozoic era;(2)the karst hydrothermal enrichment varies significantly between the basin’s margin and its interior.On the basin margin,the enrichment is largely driven by groundwater activity and faults,particularly where faults facilitate the upwelling of geothermal water.In contrast,within the basin’s interior,karst hydrothermal resources are predominantly influenced by buried hills and are especially enriched in areas facilitating the discharge of deep geothermal waters.
基金supported by National Natural Science Foundation of China(32060372,32360421)Guizhou Science and Technology Department(Qian Ke He Ji Chu ZK-[2023]Key 029Qiankehe Zhicheng[2021]Yiban462)。
文摘Soil erosion is a prominent environmental problem in karst regions.Exploring the spatiotemporal variability of soil erosion and the factors that influence soil erosion is of great significance for regional soil erosion prevention and control.However,the mechanisms influencing the characteristic features of the karst basins,such as bedrock exposure and lithology,still need to be further explored.This study used GIS technology,the Revised Universal Soil Loss Equation model,Getis–Ord Gi*,and partial least squares regression(PLSR)to identify the dominant factors influencing soil erosion and the spatiotemporal variability of soil erosion in 31 sub-basins of the Dabang River Basin(DRB),a typical karst area of Southwest China,from 2010 to 2020.The results indicated that soil erosion in the DRB from 2010 to 2020 was generally decreasing,the mean soil erosion in the DRB in 2010,2015 and 2020 was 18.46,16.51 and 15.29 t ha^(-1)a^(-1),respectively.During the study period,the area of slight erosion increased by 26.39%(706.54 km^(2)),while severe erosion enlarged by 26.36 km^(2).Spatially,the DRB was primarily affected by medium and slight soil erosion.The hot spot areas of soil erosion(key control areas)were mainly concentrated in the central and southern parts of the basin,decreasing each year,and the area of soil erosion hot pots has decreased from 43.22%to 20.60%.PLSR decoupling results show that elevation,bedrock exposure,land use type,interbedded limestone and clastic rock,and vegetation coverage were identified as the key variables affecting soil erosion,explaining 52.8%of soil erosion variability,with a high value of the Variable Importance on Projection(VIP)more than 1.These results can be used as a reference for comprehensive control of soil erosion and water loss in the basin.
基金The National Natural Science Foundation of China under contract No.42276066the Key Research and Development Program(International Science and Technology Cooperation Development Program)of Hainan Province under contract No.GHYF2022009the Youth Innovation Promotion Association of CAS under contract No.2018401.
文摘Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift normal fault through detailed seismic interpretation and fault modeling.A total of 289 post-rift normal faults were identified in the study area and can be classified into four types:(1)isolated normal faults above the carbonate platform;(2)isolated normal faults cutting through the carbonate platform;(3)conjugate normal faults,and(4)connecting normal faults.Throw distribution analysis on the fault planes show that the vertical throw profiles of most normal fault exhibit flat-topped profiles.Isolated normal faults above the carbonate platform exhibit roughly concentric ellipses with maximum throw zones in the central section whereas the normal faults cutting through the carbonate platform miss the lowermost section due to the chaotic seismic reflections in the interior of the carbonate platform.The vertical throws of conjugate normal faults anomalously decrease toward their intersection region on the fault plane whereas the connecting normal faults present two maximum throw zones in the central section of the fault plane.According to the symmetric elliptical distribution model of fault throw,an estimation was made indicating that normal faults cutting through the carbonate platform extended downward between-1308 s and-1780 s(two-way travel time)in depth and may not penetrate the entire Liuhua carbonate platform.Moreover,it is observed that the distribution of karst caves on the top of the carbonate platform disaccord with those of hydrocarbon reservoirs and the post-rift normal faults cutting through the carbonate platform in the study area.We propose that these karst caves formed most probably by corrosive fluids derived from magmatic activities during the Dongsha event,rather than pore waters or hydrocarbons.
文摘The growth of society and population has led to a range of water pollution issues.Among these,non-point source pollution assessment and treatment pose a particular challenge due to its formation mechanism.This has become a focal point and challenge in water pollution treatment research.The study area for this research was the Huanghou basin in Guizhou Province,southwest China.The land use type of the basin was analyzed using remote sensing technology,and water quality data was collected by distributing points throughout the basin,based on source-sink landscape theory.The distribution map of the basin’s source-sink landscape and the results of water quality data accurately and efficiently identified the areas with high risk of non-point source pollution in the western and southwestern residential and agricultural areas of the upper basin.Hence,a strategy of“increasing sinks and decreasing sources”was proposed.The strategy was implemented at both macro and micro levels to address non-point source pollution in the basin using ecological remediation techniques.The work to control karst rocky desertification should continue at a macro level.The rocky desertification area in the basin should gradually transform into grassland and forested land,while increasing the overall area of the sink landscape.Ecological restoration techniques,such as slope planting,riparian zone vegetation restoration,increasing plant abundance,and restoring aquatic plants,can effectively control non-point source pollution at the micro level.Compared to traditional control methods,this remediation strategy focuses on source and process control.It is more effective and does not require large-scale water pollution control projects,which can save a lot of environmental control funds and management costs.Therefore,it has greater research significance and application value.
基金This project is the applied fundamental research projects (04A10101) sponsored by the scientific and technology developmentdepartment of CNPC.
文摘Carbonate karst reservoir is the emphases of Tarim＇s carbonate exploration. However, it is buried at a large depth, which results in Weak seismic reflection signal and low S/N ratio. In addition, the karst reservoir contains great heterogeneity, so reservoir prediction is very difficult. Through many years of research and exploration, we have established a suite of comprehensive evaluation technology for carbonate karst reservoir using geophysical characteristics and a geological concept model, including a technique for reconstructing the paleogeomorphology of buried hills based on a sequence framework, seismic description of the karst reservoir, and strain variant analysis for fracture estimation. The evaluation technology has been successfully applied in the Tabei and Tazhong areas, and commercial production of oil and gas has been achieved. We show the application of this technology in the Lunguxi area in North Tarim in this paper.
文摘Accurate assessment of soil loss caused by rainfall is essential for natural and agricultural resources management. Soil erosion directly affects the environment and human sustainability. In this work, the empirical and contemporary model of revised universal soil loss equation （RUSLE） was applied for simulating the soil erosion rate in a karst catchment using remote sensing data and geographical information systems. A scheme of alterative sub-models was adopted to calculate the rainfall erosivity （R）, soil erodibility （K）, slope length and steepness （LS）, cover management （C） and conservation practice （P） factors in the geographic information system （GIS） environment. A map showing the potential of soil erosion rate was produced by the RUSLE and it indicated the severe soil erosion in the study area. Six classes of erosion rate are distinguished from the map： 1） minimal, 2） low, 3） medium, 4） high, 5） very high, and 6） extremely high. The RUSLE gave a mean annual erosion rate of 30.24 Mg ha-1 yr-1 from the 1980s to 2000s. The mean annual erosion rate obtained using RUSLE is consistent with the result of previous research based on in situ measurement from 1980 to 2009. The high performance of the RUSLE model indicates the reliability of the sub-models and possibility of applying the RUSLE on quantitative estimation. The result of the RUSLE model is sensitive to the slope steepness, slope length, vegetation factors and digital elevation model （DEM） resolution. The study suggests that attention should be given to the topographic factors and DEM resolution when applying the RUSLE on quantitative estimation of soil loss.
文摘The influence of land use and land cover on ecological environment is a focus of global change research. The paper chooses an industrial city-Shuicheng in Guizhou Province-as a study area because the karst water quality around the city is deteriorating with land use and land cover change. The natural susceptibility of karst water system is an important factor leading to karst water pollution. But land use and land cover change is also a main factor according to the chemical analysis of karst water quality and land use change. So it is a good way to protect karst water through rational planning and managing of land use and land cover.
基金Supported by the China National Science and Technology Major Project(2016ZX05014002-007)National Natural Science Foundation of China(U1663204/42072171/41772103)。
文摘Based on a large number of drilling,logging,seismic and production data,the differential structures of karst zone and hydrocarbon distribution in different paleogeomorphic units of the Tahe area,Tarim Basin,are discussed by analyzing the karst drainages and flowing channels.The karst paleogeomorphy of Ordovician in Tahe area is composed of watershed,karst valley and karst basin.The watershed has epikarst zone of 57.8 m thick on average and vadose karst zone of 115.2 m thick on average with dense faults,fractures and medium-small fracture-caves,and 76.5%of wells in this area have cumulative production of more than 5×10^(4) t per well.The karst valleys have epikarst zone,vadose karst zone and runoff karst zone,with an average thickness of 14.6,26.4 and 132.6 m respectively.In the runoff karst zone,the caves of subsurface river are mostly filled by fine sediment,with a filling rate up to 86.8%,and 84.9%of wells in this area have cumulative production of less than 2×10^(4) t per well.The karst basin has no karst zone,but only fault-karst reservoirs in local fault zones,which are up to 600 m thick and closely developed within 1 km around faults.Different karst landforms have different water flowing pattern,forming different karst zone structures and resulting in differential distribution of oil and gas.The watershed has been on the direction of oil and gas migration,so medium-small sized connected fracture-caves in this area have high filling degree of oil and gas,and most wells in this area have high production.Most caves in subsurface river are filled due to strong sedimentation and transportation of the river,so the subsurface river sediment has low hydrocarbon abundance and more low production oil wells.The faults linking source rock are not only the water channels but also the oil-gas migration pathways,where the karst fractures and caves provide huge reservoir space for oil and gas accumulation.
基金supported by the National Natural Science Fund(grants No.41272159 and 41572099)Geological Survey Project of China Geological Survey (grant No.1212011120964)
文摘Objective Complex geological factors have been constraining the oil and gas exploration in the Paleozoic strata of the Qaidam Basin,although there are high-quality hydrocarbon source rocks.One of the most important reasons may be reservoir densification due to the multiple stages of destructive cementation,which has hindered our understanding of the Paleozoic petroleum enrichment rules in the Qaidam basin.In recent years.
基金Supported by the China National Science and Technology Major Project(2016ZX05004006-001-002)CNPC-Southwest Petroleum University Innovation Consortium Technology Cooperation Project
文摘To further ascertain the origin of the Ordovician Majiagou Formation reservoirs in the Ordos Basin,the M54-M51 sub-members of the Ordovician Majiagou Formation in the eastern Sulige gasfield of Ordos Basin were taken as examples to analyze the vertical development characteristics of eogenetic karst and to discover the dissolution mechanism and its control on reservoirs through observation of a large number of cores and thin sections.According to detailed analysis of petrologic characteristics,the reservoir rock types include micritic dolomite,grain dolomite and microbialite which have mainly moldic pore,intergranular(dissolved)pore,and(dissolved)residual framework pore as main reservoir space respectively.The study area developed upward-shallowing sequences,with an exposure surface at the top of a single upward-shallowing sequence.The karst systems under the exposure surface had typical exposure characteristics of early dissolution and filling,indicating these reservoirs were related to the facies-controlled eogenetic karstification.With the increase of karstification intensity,the reservoirs became worse in physical properties.
基金Supported by the National Science and Technology Major Project of China(2016ZX05015)PetroChina Science and Technology Project(2021DJ1504).
文摘The reservoir space,types and distribution characteristics of karst carbonate gas reservoirs in the fourth member of Sinian Dengying Formation(Deng 4 Member)in central Sichuan Basin are analyzed based on the drilling,logging and seismic data.A development model of karst reservoirs is constructed to support the high-efficiency development of gas pools.The research shows that the reservoirs in Deng 4 Member have mainly small-scale karst vugs and fractures as storage space,and can be divided into three types,fracture-vug,pore-vug and pore types.The development patterns of the karst reservoirs are determined.On the plane,the karst layers increase from 65 m to 170 m in thickness from the karst platform to the karst slope,and the high-quality reservoirs increase from 25.0 m to 42.2 m in thickness;vertically,the reservoirs at the top of Deng 4 Member appear in multiple layers,and show along-bedding and along fracture dissolution characteristics.The reservoirs at the bottom are characterized by the dissolution parallel to the water level during the karstification period,and have 3-5 large-scale fracture-cave systems.Based on the reservoir development characteristics and the genetic mechanism,three types of reservoir development models of karst reservoir are established,i.e.,bed-dissolved body,fracture-dissolved body and paleohorizon-dissolved body.The construction of karst reservoir development models and seismic response characteristics of the three types of reservoirs can provide parameter for well placement and trajectory design,and substantially improve productivity and development indices of individual wells and gas reservoirs.The designed production capacity of the gas reservoir has enhanced from the initial 3.6 billion to 6 billion cubic meters,making the profit of the reservoir development increase noticeably.
基金Supported by the PetroChina Science and Technology Project(KT2018-01-02)
文摘Based on the analysis of the responses of conventional logs such as natural gamma(GR), density(DEN), acoustic interval transit time(AC), compensated neutron(CNL), dual lateral resistivity(Rlld, Rlls), and caliper log(CAL), combined with drilling data,cores, thin section and productivity of 65 wells, the reservoirs in the Mid-Permian Maokou Formation of southern Sichuan Basin were divided into four types, fractured-vuggy, pore-vuggy, fractured and fractured-cavity. The main reservoirs in high productivity wells are fractured-vuggy and pore-vuggy. The reservoirs of Maokou Formation are generally thin, and can be divided into the upper reservoir segment(layer a of the second member to the third member of Maokou Formation, P_2 m^2 a-P_2 m^3) and the lower segment(layer b of the second member of Maokou Formation, P_2 m^2 b). The two reservoir segments are mainly controlled by two grain beaches during the sedimentation of P_2 m^2 a-P_2 m^3 and P_2 m^2 b, the vertical zonation of karst, and the fractures. The upper reservoir segment is generally better than the lower one in development degree and single well productivity, and is much thicker than the lower one. It is thicker in the Yibin-Zigong-Weiyuan-Dazu area, the southwestern area of Chongqing and the southeastern area of Luzhou, while the lower segment is thicker in the Neijiang-Zigong-Luzhou area and the Dazu-Luzhou area. The areas with big reservoir thickness at tectonic slope or syncline parts are the favorable exploration areas.
基金Supported by the National Major Science and Technology Project(2016ZX05007004)PetroChina Southwest Oil&Gas Field Branch Company Science and Technology Project(2019ZD01)。
文摘Based on outcrop, drilling, logging, geochemical analysis and seismic data, the karst landform and distribution of Permian volcanic rocks at the end of the sedimentary period of the Maokou Formation in the western Sichuan Basin are examined, and their petroleum geological significance is discussed. Affected by normal faults formed in the early magmatic activities and extension tectonic background in the late sedimentary period of the Maokou Formation, a local karst shallow depression under the background of karst slope came up in the Jianyang area of the western Sichuan Basin, where the residual thickness of the Maokou Formation was thinner. Basic volcanic rocks like pyroclastic rock of eruptive facies, basalt of overflow facies, diabase porphyrite of intrusive facies and sedimentary tuff of volcanic sedimentary facies were formed after karstification. However, under the effects of faulting and karst paleogeomorphology, the volcanic rocks in different areas had different accumulation features. In the Jianyang area, with long eruption time, the volcanic rocks were thick and complex in lithology, and accumulated in the karst depressions. In the Zhongjiang-Santai area located in the karst slope, there’s no fault developed, only thin layers of basalt and sedimentary tuff turned up. The karst landform controls the build-up of thick explosive facies volcanic rocks and also the development of karst reservoirs in the Maokou Formation, and the western Sichuan area has oil and gas exploration potential in volcanic rocks and the Maokou Formation.
基金This work was supported by the Fundamental Research Funds for the Chinese Academy of Geosciences(No.JYYWF20180401)the China Geological Survey project(No.DD20160296,DD20201123).
文摘The changes of development and utilization of karst groundwater in Sangu Spring Basin have made the original groundwater resource evaluation unable to meet the needs of future economic development.Based on analysis of existing data,combined with the characteristics of supplement,runoff and draining of regional karst groundwater,the Visual Modelflow software was used to build a numerical simulation model of Sangu spring Basin.The amount of karst groundwater resource and groundwater environment of the Basin were evaluated under different exploitation schemes,and the changes of karst groundwater environment in the future ten years were also predicted.The fitting error which is less than 0.5 m between the calculated value and measured value of the water level in the fitted borehole accounts for 93%.For the lithologically and structurally complex Sangu Spring Basin,the fitting effect of numerical simulation model was ideal.On the basis of the current mining amount of 111.80 million m3/a,the total redistributed exploited amount in the spring region was 61.79 million m3/a.Under the condition that the quantity of recoverable resources reached 173.59 million m3/a and under different precipitation schemes,all constraint conditions were satisfied,such as regional water level drawdown,maximum allowable water level drawdown in every simulated water source area and the flow rate of Guobi Spring.The results will provide a scientific basis for the rational development and utilization of karst groundwater in Sangu Spring Basin.
基金financially supported by the National Science Foundation of China(grant No.41372146)
文摘Objective Oil and gas are abundant in the Ordovician Yingshan Formation carbonate karst reservoirs on the northern slope of Tazhong uplift in the Tarim Basin, and have extremely complicated oil-gas-water distribution, however. The difference in burial depth of the reservoirs between east and west sides is up to 1000 m. Water-bearing formations exist between oil- and gas-bearing formations vertically and water-producing wells are drilled between oil- and gas-producing wells. Macroscopically, oil and gas occur at low positions, while water occurs at high positiona on the northern slope of Tazhong uplift. The mechanism of differential hydrocarbon enrichment in heterogeneous reservoirs is by far not clarified, which has affected the efficient exploration and development of oil and gas fields in this area.
文摘In karst area water deficit is one of the main factors constraining sustainable economic development. In 1979 the comprehensive karstic observational field station was set up in Houzhai drainage basin located,\ in Puding county of Guizhou Province, which can represent most of the small karst drainage basins on the dividing line of the Guizhou Plateau. Geomorphology, water resources and water chemistry were investigated and observed. Based on comparisons of water supply with water demand and analysis of the main problems in water exploitation and utilization. it is found out that the water deficiency was not directly caused by the scarcity of natural water resources. The true reason is the insufficient capacity of water supply caused by the dismatch of the water and soil water resources which can be dealt with by building more irrigation works. Some solutions such as to build scientific basis for water exploitation and utilization and sustainable economic development in karst drainage basins on dividing line of the Guizhou Plateau.
基金Supported by the National Natural Science Foundation Project of China(U22B6002)Prospective Basic Technology Research Project of PetroChina(2021DJ0605).
文摘Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.
基金financially supported by the China Geological Survey(Grant No.DD20190107,DD20190094)。
文摘In the Qaidam basin,Northwest China,karstic fissures and caves are developed in many places of the Lower Carboniferous Chengqianggou Fm.and Huaitoutala Fm.and the Upper Carboniferous Keluke Fm.,in which are found typical karstic marks.Several suites of transgressive carbonate rocks formed during the Late Paleozoic epoch are preserved as reservoir properties in the Qaidam basin,with paleokarst-related cave-fractured diagenetic structures,which provided the basis for cavefractured development.Carbonate and clastic samples covering or infilling caves and fractures in Carboniferous strata were collected in the eastern Qaidam basin to focus on petrological and geochemical analyses of karst and infilling materials.Based on this study of the Caledonian diagenetic sequence,and bitumen-infilled inclusion temperature and burial history,there existed a continuous atmospheric freshwater leaching process,which played a critical role in the construction of the Carboniferous supergene paleokarsts.Investigation and survey of the tectonic setting,plate paleolatitude and river development intensity also proves that there was abundant rainfall during the Indosinian period,after which the strata undergo a shallow burial process.Because Indosinian period is earlier than the key timing of hydrocarbon-generation of the Carboniferous source rocks,this kind of karst reservoir has potential significance for oil-gas resources in this area.
文摘In Karst drainage basins, there are the ground water and underground water exchanging frequently, and the shortage of water resources due to having the special double aquifer mediums and unique surface and subsurface river systematic structure. This paper is to select 20 research sampling areas coming fromGuizhouProvince, and according to the spectral characteristics of the catchment water-holding mediums and vegetations, and using the remote sensing technique, extract the watershed vegetation index. According to the principle of principal component analysis, using the software of Spss and Matlab is to analyze the impacts of watershed vegetation type on the catchment water-holding ability, and establish the principal component analysis function. Studies have shown that: 1) the watershed vegetation coverage rate plays an important role in Karst basin water-holding ability;2) the catchment water-holding ability is the comprehensive reflection and manifestation of the Catchment Water-storing Capacity (CWC);3) it is much better effects and higher accuracy to monitor/forecast the catchment water-holding volume by using the vegetation indices.
基金Supported by the National Natural Science Foundation of China(U1663204)National Major Oil and Gas Project(2016ZX05014002-007)。
文摘Based on a large number of geological and geophysical data,the formation,fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area,Tarim Basin,are discussed by analyzing faults and strata thickness.The hoodoo-upland was made of high peaks and narrow valleys in the Ordovician karst slope during the Early Hercynian karst period,which were distributed along the NNE positive flower structure and had inherited evolution.The fault-fractures and fracture-vugs complex were extremely developed,with a thickness of 100 m.The cumulative oil production of 60% oil wells was more than 20×10^(4) t per well in the hoodoo-upland,where the residual thickness of the Ordovician Yingshan Formation was greater than karst depressions.Caves formed by the shelter of collapsed breccias were developed in the valleys.They were 1.6 to 13.5 m high,with a filling rate of 51.6%.The positive flower structure under the settings of strike-slip compression controlled the early formation of the hoodoo-upland on the karst slope,resulting in the differences of drainage distribution and karstification.Compared with the water-rich karst valley,the hoodoo-upland with lean water suffered weaker karstification,had thicker residual stratum,and was higher in terrain.In rainy season,the meteoric water flew and corrode along the cracks,forming a complex network of fractures and caves.Combined with inherited uplift and the effective match of the NNE deep faults,oil and gas continuously charged into the reservoir space in the upland,forming the hoodoo fracture-cave reservoir with vertically quasi continuous distribution,high hydrocarbon abundance and high production.
