A comparative study of the main factors controlling geohazards induced by 10 strong earthquakes in Western China since the Wenchuan earthquake in 2008

Determining the main controlling factors of earthquake-triggered geohazards is a prerequisite for studying earthquake geohazards and post-disaster emergency response.By studying these factors,the geomorphic and geological factors controlling the nature,condition,and distribution of earthquake-induced geohazards can be analyzed.Such insights facilitate earthquake disaster prediction and emergency response planning.The authors combined field investigations and spatial data analysis to examine geohazards induced by seismic events,examining ten earthquakes including the Wenchuan,Yushu,Lushan events,to elucidate the main control factors of seismic geohazard.The authors observed that seismic geohazard occurrence is usually affected by many factors,among which active nature of the seismogenic fault,seismic peak ground acceleration(PGA),topographic slope and geomorphic height differences,and distance from the fault zone and river system are the most important.Compared with strike-slip earthquakes,thrust earthquakes induce more high-altitude and high-speed remote landslides,which can cause great harm.Slopes of 0°–40°are prone to secondary seismic geohazards,which are mainly concentrated 0–6 km from the river system.Secondary geohazards are not only related to seismogenic fault but also influenced by the associated faults in the earthquake area.The maximum seismic PGA and secondary seismic geohazard number are positively correlated,and the horizontal and vertical ground motions play leading and promoting roles in secondary geohazard formation,respectively.Through the research,the spatial distribution of seismic geohazards is predicted,providing a basis for the formulation of emergency response plans following disasters.

Enrichment model and major controlling factors of below-source tight oil in Lower Cretaceous Fuyu reservoirs in northern Songliao Basin,NE China

Based on the geochemical,seismic,logging and drilling data,the Fuyu reservoirs of the Lower Cretaceous Quantou Formation in northern Songliao Basin are systematically studied in terms of the geological characteristics,the tight oil enrichment model and its major controlling factors.First,the Quantou Formation is overlaid by high-quality source rocks of the Upper Cretaceous Qingshankou Formation,with the development of nose structure around sag and the broad and continuous distribution of sand bodies.The reservoirs are tight on the whole.Second,the configuration of multiple elements,such as high-quality source rocks,reservoir rocks,fault,overpressure and structure,controls the tight oil enrichment in the Fuyu reservoirs.The source-reservoir combination controls the tight oil distribution pattern.The pressure difference between source and reservoir drives the charging of tight oil.The fault-sandbody transport system determines the migration and accumulation of oil and gas.The positive structure is the favorable place for tight oil enrichment,and the fault-horst zone is the key part of syncline area for tight oil exploration.Third,based on the source-reservoir relationship,transport mode,accumulation dynamics and other elements,three tight oil enrichment models are recognized in the Fuyu reservoirs:(1)vertical or lateral migration of hydrocarbon from source rocks to adjacent reservoir rocks,that is,driven by overpressure,hydrocarbon generated is migrated vertically or laterally to and accumulates in the adjacent reservoir rocks;(2)transport of hydrocarbon through faults between separated source and reservoirs,that is,driven by overpressure,hydrocarbon migrates downward through faults to the sandbodies that are separated from the source rocks;and(3)migration of hydrocarbon through faults and sandbodies between separated source and reservoirs,that is,driven by overpressure,hydrocarbon migrates downwards through faults to the reservoir rocks that are separated from the source rocks,and then migrates laterally through sandbodies.Fourth,the differences in oil source conditions,charging drive,fault distribution,sandbody and reservoir physical properties cause the differential enrichment of tight oil in the Fuyu reservoirs.Comprehensive analysis suggests that the Fuyu reservoir in the Qijia-Gulong Sag has good conditions for tight oil enrichment and has been less explored,and it is an important new zone for tight oil exploration in the future.

Study on Influencing Factors and Control Points of Design Estimate of Landscaping Engineering

In recent years,China’s landscaping projects have developed vigorously,and the growth rate of urban garden green space areas has been maintained at about 5%.Overall,with the development of the national economy and the support of macro policies,people’s demand for close to nature and beautify the environment is gradually increasing,which has brought new growth momentum for the development of the landscaping industry.Simultaneously,from the perspective of future economic development and urban development,the landscaping industry still has a lot of room for development.However,with the rapid development of landscape engineering,the problem of cost control of landscape engineering is becoming more prominent,the phenomenon of budget overestimation is common,and there are many factors affecting the cost of landscape engineering,which brings difficulties and challenges to the analysis of its influencing factors and cost management.How to scientifically analyze the influencing factors and control the cost has become an important link in the landscaping project.To solve the above problems,this paper takes the design stage of landscaping engineering as the background,takes the design estimate of landscaping engineering as the research object,through literature research and data collection,fully excavates the main influencing factors of the design estimate stage of landscaping engineering,analyzes the key points of cost control,and provides reference ideas and directions for the later cost management and control.

Differential Hydrocarbon Enrichment and its Main Controlling Factors in Depressions of the Bohai Bay Basin Differential Hydrocarbon Enrichment and its Main Controlling Factors in Depressions of the Bohai Bay Basin

Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin.There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon generation, migration and accumulation, contains significantly different hydrocarbon generation conditions and enrichment degree. On the basis of previous documents and a large number of statistical data, this work comparatively analyzed the differential hydrocarbon enrichment and its major controlling factors in depressions of the Bohai Bay Basin. The results show that depressions in the Bohai Bay Basin have various hydrocarbon enrichment degrees, and can be categorized into four types, namely enormously oil-rich, oil-rich, oily and oil-poor depressions. In general, the enormously oil-rich and oil-rich depressions are distributed in the eastern part of the basin along the Tan-Lu and Lan-Liao faults, whereas depressions in the western part of the basin are poor in hydrocarbons. Moreover, the vertical distribution of hydrocarbons is also highly heterogeneous, with Pre-Paleogene strata rich in hydrocarbons in the northern and western depressions, Paleogene strata rich in hydrocarbons in the entire basin, and Neogene strata rich in hydrocarbons in the off-shore areas of the Bohai Bay Basin. From early depressions in onshore areas to the late depressions in offshore areas of the Bohai Bay Basin, the source rocks and source-reservoir-cap rock assemblages gradually become younger and shallower, and the hydrocarbon resource abundance gradually increases. Hydrocarbon supplying condition is the key factor constraining the hydrocarbon enrichment for different depressions,while the main source-reservoir-cap rock assemblage, sufficient hydrocarbons and the transportation capacity of faults control the vertical distribution of hydrocarbons. The main factors controlling hydrocarbon enrichment are different for different layers. The hydrocarbon supplying condition of source rocks is the key controlling factor, whereas the source-reservoir configuration, the main sourcereservoir-cap rock assemblages, and the fault transportation are the main factors of hydrocarbon enrichment in the Paleogene, Paleogene and Neogene, respectively.

Main geological and mining factors affecting ground cracks induced by underground coal mining in Shanxi Province, China

As one of the largest coal-rich provinces in China,Shanxi has extensive underground coal-mining operations.These operations have caused numerous ground cracks and substantial environmental damage.To study the main geological and mining factors influencing mining-related ground cracks in Shanxi,a detailed investigation was conducted on 13 mining-induced surface cracks in Shanxi.Based on the results,the degrees of damage at the study sites were empirically classified into serious,moderate,and minor,and the influential geological and mining factors(e.g.,proportions of loess and sandstone in the mining depth,ratio of rock thickness to mining thickness,and ground slope)were discussed.According to the analysis results,three factors(proportion of loess,ratio of rock thickness to mining thickness,and ground slope)play a decisive role in ground cracks and can be respectively considered as the critical material,mechanical,and geometric conditions for the occurrence of mining surface disasters.Together,these three factors have a strong influence on the occurrence of serious discontinuous ground deformation.The results can be applied to help prevent and control ground damage caused by coal mining.The findings also provide a direct reference for predicting and eliminating hidden ground hazards in mining areas.

Main Controlling Factors and Accumulation Model of Chang 9 Reservoir in Northwest Ordos Basin, China

In northwestern Ordos Basin, the Triassic reservoir Chang 9 has favorable reservoir forming conditions, extensive reservoir development, and huge potential for oil exploration and exploitation. Studying the main controlling factors and accumulation model of Chang 9 reservoir in this area can provide a basis for the production targets, and assist in formulating reasonable development technology policy. In this paper, to explore and summarize the hydrocarbon accumulation model, the Chang 9 reservoir were analyzed from the aspects of oil source, fracture, oil migration, structure, lithology and reservoir physical properties for the main controlling factors in this area. Organic geochemical and geological comprehensive analysis that the oil-source of the Chang 9 reservoir in the northwest of Ordos Basin is derived from Chang 7 hydrocarbon source rocks. The fractures provide a sound channel for the "vertical multi-point filling" of the oil source from Chang 7 to Chang 9. The crude oil migrates vertically from Chang 7 to Chang 9, then expands horizontally to form a reservoir. Structures play an important role in controlling the distribution of reservoirs, the control by sand in small layer and physical property is also obvious. This paper creatively establishes the reservoir accumulation model of Chang 9 in northwest of Ordos Basin, which is characterized by Vertical multi-point filling, horizontal expansion becomes oil pool. It reveals the genetic mechanism of the development of Chang 9 multi-reservoir in the study area, which provides guidance for exploration and evaluation deployment.

Fractal Characteristics and Main Controlling Factors of High-Quality Tight Sandstone Reservoirs in the Southeastern Ordos Basin

Due to the complex conditions and strong heterogeneity of tight sandstone reservoirs,the reservoirs should be classified and the controlling factors of physical properties should be studied.Cast thin section observations,cathodoluminescence,scanning electron microscopy(SEM),X-ray diffraction(XRD),and high-pressure mercury injection(HPMI)were used to classify and optimize the reservoir.The Brooks-Corey model and stepwise regression were used to study the fractal dimension and main controlling factors of the physical properties of the high-quality reservoir.The results show that the reservoirs in the study area can be divided into four types,and the high-quality reservoir has the best physical properties and pore-throat characteristics.In the high-quality reservoir,the homogeneity of transitional pores was the best,followed by that of micropores,and the worst was mesopores.The porosity was controlled by depth and kaolinite.The model with standardized coefficients is y=12.454−0.778×(Depth)+0.395×(Kaolinite).The permeability was controlled by depth,illite/montmorillonite,and siliceous cement,and the model with standardized coefficients is y=1.689−0.683×(Depth)−0.395×(Illite/Montmorillonite)−0.337×(Siliceous Cement).The pore-throat evolutionary model shows that the early-middle diagenetic period was when the reservoir physical properties were at their best,and the kaolinite intercrystalline pores and residual intergranular pores were the most important.

Evaluation and Application of Flowback Effect in Deep Shale Gas Wells

The pivotal areas for the extensive and effective exploitation of shale gas in the Southern Sichuan Basin have recently transitioned from mid-deep layers to deep layers.Given challenges such as intricate data analysis,absence of effective assessment methodologies,real-time control strategies,and scarce knowledge of the factors influencing deep gas wells in the so-called flowback stage,a comprehensive study was undertaken on over 160 deep gas wells in Luzhou block utilizing linear flow models and advanced big data analytics techniques.The research results show that:(1)The flowback stage of a deep gas well presents the characteristics of late gas channeling,high flowback rate after gas channeling,low 30-day flowback rate,and high flowback rate corresponding to peak production;(2)The comprehensive parameter AcmKm1/2 in the flowback stage exhibits a strong correlation with the Estimated Ultimate Recovery(EUR),allowing for the establishment of a standardized chart to evaluate EUR classification in typical shale gas wells during this stage.This enables quantitative assessment of gas well EUR,providing valuable insights into production potential and performance;(3)The spacing range and the initial productivity of gas wells have a significant impact on the overall effectiveness of gas wells.Therefore,it is crucial to further explore rational well patterns and spacing,as well as optimize initial drainage and production technical strategies in order to improve their performance.

Natural Gas Types,Distribution Controlling Factors,and Future Exploration in the Western Qaidam Basin

The Paleogene and Neogene oil and gas in the western Qaidam basin have a regular distribution in three concentric zones from the edge to the center of the basin. Natural gas mainly occurs in the inner zone, and the gas-oil ratio of the northern area of the basin is significantly higher than that of the southern area. Large amounts of carbon isotope data of natural gas, plotted in X- shaped and comprehensive identification diagrams for the southern area and northern area, respectively, were used to identify the types of natural gas. The large-scale distribution of natural gas is highly consistent with the Ro values of major source rocks, but is poorly correlated with the type of organic matter. This indicates that the main controlling factor of natural gas distribution is organic matter maturity, and the kerogen types act as the basis for the formation of different types of natural gas. Paleouplifts and squeezed anticlines near hydrocarbon generation depression centers, which are major natural gas-rich regions, control the migration directions of natural gas, while hydrocarbon migration pathways and fault systems connecting gas sources are the most important factors for natural gas reservoir formation in the inner basin. Therefore, favorable zones for natural gas distribution can be predicted on the basis of the distribution of thermal evolution and the gas generation intensity of major source rocks as well as the structural map. The Shizigou-Youshashan- Yingdong-Dawusi, Youquanzi -Kaitemilike - Youdunzi, and Xiaoliangshan - Nanyishan - Dafengshan structural belts are favorable zones for natural gas accumulation. This study has important theoretical and practical significance for future natural gas exploration.

Enrichment of tight oil and its controlling factors in central and western China

Taking the tight oil of the Zhongnan sag in the Ordos Basin,Jimusar sag in the Junggar Basin and Qingxi sag in the Jiuquan Basin as study objects,based on field survey,dissection of tight oil reservoirs,sample test,modeling experiment and comprehensive analysis,this study reveals that the tight oil accumulates at start-up pressure,advances under differential pressure,diffuses at alternating fast and low speeds,charges in stepped large area and migrates rapidly through fractures,and enriches in dominant fractures and pores.The root cause of ladder-like charge is the multiple scales of pores.The widespread source rock with high hydrocarbon generation intensity is the material basis for tight oil enrichment;the dominant source reservoir assemblage is the basic unit for tight oil enrichment;fractures and beddings are conducive to local rapid migration of tight oil;fractures and pores work together to control the enrichment of tight oil.Two typical accumulation models of tight oil are established,namely"source reservoir in coexistence,four optimal factors controlling enrichment around central area,and large-scale continuous distribution"for a large freshwater lake clastic rock basin and"source reservoir integration,four optimal factors controlling enrichment,central area distribution,small in size but high in enrichment degree"for a small saline lake diamictite depression.

Controlling factors of marine shale gas differential enrichment in southern China

Based on the exploration and development practice of marine shale gas in Fuling, Weiyuan, Changning, Luzhou and Southeast Chongqing in southern China, combined with experiments and analysis, six factors controlling differential enrichment of marine shale gas are summarized as follows:(1) The more appropriate thermal evolution and the higher the abundance of organic matter, the higher the adsorption and total gas content of shale will be.(2) Kerogen pyrolysis and liquid hydrocarbon cracking provide most of the marine shale gas.(3) The specific surface area and pore volume of organic matter rich shale increased first and then decreased with the increase of thermal evolution degree of organic shale. At Ro between 2.23% and 3.33%, the shale reservoirs are mainly oil-wet, which is conducive to the enrichment of shale gas.(4) The thicker the roof and floor, the higher the shale gas content. The longer the last tectonic uplift time and the greater the uplift amplitude, the greater the loss of shale gas will be.(5) The buried depth and dip angle of the stratum have different controlling and coupling effects on shale gas in different tectonic positions, resulting in two differential enrichment models of shale gas.(6) The effective and comprehensive matching of source, reservoir and preservation conditions determines the quality of shale gas accumulation. Good match of effective gas generating amount and time, moderate pore evolution and good preservation conditions in space and time is essential for the enrichment of shale gas.

Elemental characteristics of lacustrine oil shale and its controlling factors of palaeo-sedimentary environment on oil yield： a case from Chang 7 oil layer of Triassic Yanchang Formation in southern Ordos Basin

As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.

Major controlling factors and hydrocarbon accumulation models of large-scale lithologic reservoirs in shallow strata around the Bozhong sag,Bohai Bay Basin,China

Based on the practice of oil and gas exploration and the analysis of shallow lithologic reservoirs,combined with the allocation relationship and enrichment law of oil and gas accumulation factors,main controlling factors and models of hydrocarbon accumulation of large lithologic reservoirs in shallow strata around the Bozhong sag are summarized,and favorable exploration areas are proposed.The coupling of the four factors of“ridge-fault-sand-zone”is crucial for the hydrocarbon enrichment in the shallow lithologic reservoirs.The convergence intensity of deep convergence ridges is the basis for shallow oil and gas enrichment,the activity intensity of large fault cutting ridges and the thickness of cap rocks control the vertical migration ability of oil and gas,the coupling degree of large sand bodies and fault cutting ridges control large-scale oil and gas filling,the fault sealing ability of structural stress concentration zones affects the enrichment degree of lithologic oil and gas reservoirs.Three enrichment models including uplift convergence type,steep slope sand convergence type and depression uplift convergence type are established through the case study of lithologic reservoirs in shallow strata around the Bozhong sag.

Differences and controlling factors of composite hydrocarbon accumulations in the Tazhong uplift, Tarim Basin, NW China

Based on three-dimensional seismic interpretation, structural and sedimentary feature analysis, and examination of fluid properties and production dynamics, the regularity and main controlling factors of hydrocarbon accumulation in the Tazhong uplift, Tarim Basin are investigated. The results show that the oil and gas in the Tazhong uplift has the characteristics of complex accumulation mainly controlled by faults, and more than 80% of the oil and gas reserves are enriched along fault zones. There are large thrust and strike-slip faults in the Tazhong uplift, and the coupling relationship between the formation and evolution of the faults and accumulation determine the difference in complex oil and gas accumulations. The active scale and stage of faults determine the fullness of the traps and the balance of the phase, that is, the blocking of the transport system, the insufficient filling of oil and gas, and the unsteady state of fluid accumulation are dependent on the faults. The multi-period tectonic sedimentary evolution controls the differences of trap conditions in the fault zones, and the multi-phase hydrocarbon migration and accumulation causes the differences of fluid distribution in the fault zones. The theory of differential oil and gas accumulation controlled by fault is the key to the overall evaluation, three-dimensional development and discovery of new reserves in the Tazhong uplift.

RESEARCH ON DEEP COAL SEAM MINING FLOOR STARTA WATER BURSTING INFLUENCED FACTORS BASED ON ANALYTIC HIERACHY PROCESS

Deep coal seam mining floor strata water bursting is a complicate nonlinear system, whose factors are coupling and influencing themselves. It built the analytic structure model for deep coal seam mining floor strata water bursting, the judgment matrix was found by the expert scoring method, the contribution weights of the influenced factors were given out by the equation analytic process. The thirteen controlling factors and five main controlling factors were put award by analyzing weights, so the result was basically conform to the field practice. The expert scoring method and analytic process can convert the objective fact to the subjective cognition, so it is a method that can turn the qualitative into the quantitative. This can be relative objectively and precisely to study the question of many factors and grey box.

Division of Matrix- and Fracture-Type Shale Oils in the Jiyang Depression and Their Differences

This study discussed the division of matrix- and fracture-type shale oils in the Jiyang Depression, and proposed the concept of fracture development coefficient. The fracture development coefficient is defined as the ratio of fault throw to the distance between a shale oil well and the nearest fault. Based on CO_2 content, state of water, oil production and logging response of shale oil formations, the classification of shale oils was established, i.e., a fracture-type shale oil well has a fracture development coefficient greater than 0.2, while a matrix-type one has a fracture development coefficient less than 0.2. Furthermore, the key control factors of matrix- and fracture-type shale oil enrichment were analyzed using typical anatomical and statistical methods. For matrix-type shale oil enrichment, these factors are lithofacies, total organic carbon（TOC）, shale porosity and abnormal pressure; for fracture-type shale oil enrichment, they are lithofacies, extent of fracture development, and abnormal pressure. This study also first described the differences between matrix- and fracture-type shale oils. The results provide reference for the exploration of terrestrial faulted basins in eastern China.

Shut-in time optimization after fracturing in shale oil reservoirs

A multi-process(fracturing,shut-in and production)multi-phase flow model was derived considering the osmotic pressure,membrane effect,elastic energy and capillary force,to determine the optimal shut-in time after multi-cluster staged hydraulic fracturing in shale reservoirs for the maximum production.The accuracy of the model was verified by using production data and commercial software.Based on this model and method,a physical model was made based on the inversion of fracture parameters from fracturing pressure data,to simulate the dynamic changes of pore pressure and oil saturation during fracturing,soaking and production,examine effects of 7 factors on the optimal shut-in time,and find out the main factors affecting the optimal shut-in time through orthogonal experiments.With the increase of shut-in time,the increment of cumulative production increases rapidly first and then tended to a stable value,and the shut-in time corresponding to the inflection point of the change was the optimal shut-in time.The optimal shut-in time has a nonlinear negative correlation with matrix permeability,porosity,capillary pressure multiple and fracture length,a nonlinear positive correlation with the membrane efficiency and total volume of injected fluid,and a nearly linear positive correlation with displacement.The seven factors in descending order of influence degree on optimal shut-in time are total volume of injected fluid,capillary force multiple,matrix permeability,porosity,membrane efficiency,salinity of fracturing fluid,fracturing fluid displacement.

Application of Single-to-Single Phase Matrix Conversion in Conventional Rectifier-Inverter

The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the two conversion techniques is discovered. It is characteristic of the switch functiion to follow mains voltage distortion and mains frequency drift. By utilizing the merit, unidirectional switch duty rations of the inverter follow the variation of DC link voltage automatically, thus the size of DC link electrolytic capacitor can be reduced considerably, bringing about improved mains side power factor. Corresponding topologies and theoretical and theoretical derivations are given, and so are the simulation results, based on which it is confirmed that the single to single phase matrix conversion technique is potentially useful in large scale production, and the introduction of switch function can yield good economic returns.

Geological characteristics and exploration of shale oil in Chang 7 Member of Triassic Yanchang Formation, Ordos Basin, NW China

A set of shale-dominated source rocks series were deposited during the heyday of lake basin development in the Member 7 of Triassic Yanchang Formation,Ordos Basin,and the thickness is about 110 m.Aimed at whether this layer can form large-scale oil enrichment of industrial value,comprehensive geological research and exploration practice have been carried out for years and obtained the following important geologic findings.Firstly,widely distributed black shale and dark mudstone with an average organic matter abundance of 13.81%and 3.74%,respectively,lay solid material foundation for the formation of shale oil.Secondly,sandy rocks sandwiched in thick organic-rich shale formations constitute an oil-rich"sweet spot",the average thickness of thin sandstone is 3.5 m.Thirdly,fine-grained sandstone and siltstone reservoirs have mainly small pores of 2–8μm and throats of 20–150 nm in radius,but with a large number of micro-pores and nano-throats,through fracturing,the reservoirs can provide good conductivity for the fluid in it.Fourthly,continued high-intensity hydrocarbon generation led to a pressure difference between the source rock and thin-layer reservoir of up to 8–16 MPa during geological history,driven by the high pressure,the oil charged into the reservoirs in large area,with oil saturation reaching more than 70%.Under the guidance of the above theory,in 2019,the Qingcheng Oilfield with geologic oil reserves of billion ton order was proved in the classⅠmulti-stage superimposed sandstone shale reservoir of Chang 7 Member by the Changqing Oilfield Branch through implementation of overall exploration and horizontal well volume fracturing.Two risk exploration horizontal wells were deployed for the classⅡthick layer mud shale interbedded with thin layers of silt-and fine-sandstones reservoir in the Chang 73 submember,and they were tested high yield oil flows of more than 100 tons per day,marking major breakthroughs in petroleum exploration in classⅠshale reservoirs.The new discoveries have expanded the domain of unconventional petroleum exploration.