Excess pore pressure behavior and evolution in deep coalbed methane reservoirs

Deep coalbed methane(DCBM),an unconventional gas reservoir,has undergone significant advancements in recent years,sparking a growing interest in assessing pore pressure dynamics within these reservoirs.While some production data analysis techniques have been adapted from conventional oil and gas wells,there remains a gap in the understanding of pore pressure generation and evolution,particularly in wells subjected to large-scale hydraulic fracturing.To address this gap,a novel technique called excess pore pressure analysis(EPPA)has been introduced to the coal seam gas industry for the first time to our knowledge,which employs dual-phase flow principles based on consolidation theory.This technique focuses on the generation and dissipation for excess pore-water pressure(EPWP)and excess pore-gas pressure(EPGP)in stimulated deep coal reservoirs.Equations have been developed respectively and numerical solutions have been provided using the finite element method(FEM).Application of this model to a representative field example reveals that excess pore pressure arises from rapid loading,with overburden weight transferred under undrained condition due to intense hydraulic fracturing,which significantly redistributes the weight-bearing role from the solid coal structure to the injected fluid and liberated gas within artificial pores over a brief timespan.Furthermore,field application indicates that the dissipation of EPWP and EPGP can be actually considered as the process of well production,where methane and water are extracted from deep coalbed methane wells,leading to consolidation for the artificial reservoirs.Moreover,history matching results demonstrate that the excess-pressure model established in this study provides a better explanation for the declining trends observed in both gas and water production curves,compared to conventional practices in coalbed methane reservoir engineering and petroleum engineering.This research not only enhances the understanding of DCBM reservoir behavior but also offers insights applicable to production analysis in other unconventional resources reliant on hydraulic fracturing.

The coalbed methane production potential method for optimization of wells location selection

A gas production potential method for optimization of gas wellsite locations selection is proposed in terms of the coalbed gas resources volume and the recoverability. The method uses the actual data about reservoirs in a coalbed gas field in central China to optimize wellsite locations in the studied area in combination with the dynamic data about actual production in the coalbed gas field, selects a favorable subarea for gas wells deployment. The method is established based on the basic properties of coal reservoirs, in combination with the coalbed thickness and the gas content to make an analysis of the gas storage potential of a coal reservoir, as well as resources volume and the permeability of a coal reservoir. This method can be popularized for optimization of wellsite locations in other methane gas development areas or blocks.

Dynamic behavior of coalbed methane flow along the annulus of single-phase production

Dynamic behavior of coalbed methane (CBM) flow will provide the theoretical basis to optimize production performance for a given well.A mathematical model is developed to simulate flowing pressures and pressure drops of CBM column from well head to bottom hole.The measured parameters and independent variables of flow rates,flowing pressures and temperatures are involved in CBM producing process along the annulus.The developed relationships are validated against full-scale measured data in single-phase CBM wellbores.The proposed methodology can analyze the dynamic behavior in CBM reservoir and process of CBM flow with an overall accuracy of 2%.The calculating process of flowing pressures involves friction factor with variable Reynolds number and CBM temperature and compressibility factor with gravitational gradients.The results showed that the effect of flowing pressure on CBM column was more obvious than that on CBM and water column accompanied by an increase of dynamic water level.The ratios of flowing pressure on increment of CBM column to the whole column increased with the declined flow rates of water column.Bottom-hole pressure declined with the decreased flowing pressure of CBM column along the annulus.It will lead to the results of the increased pressure drop of CBM column and CBM flow rate in single-phase CBM wellbores.

Methods for simultaneously evaluating reserve and permeability of undersaturated coalbed methane reservoirs using production data during the dewatering stage

In this work,a flowing material balance equation(FMBE) is established for under saturated coalbed methane(CBM) reservoirs,which considers immobile free gas expansion effect at the dewatering stage.Based on the established FMBE,five straight-line methods are proposed to determine the control area,initial water reserve,initial free gas reserve,initial adsorbed gas reserve,original gas in place,as well as permeability at the same time.Subsequently,the proposed FMBE methods for undersaturated CBM reservoirs are validated against a reservoir simulation software with and without considering free gas expansion.Finally,the proposed methods are applied in a field case when considering free gas expansion effect.Validation cases show that the straight-line relationships for the proposed five FMBE methods are excellent,and good agreements are obtained among the actual reserves and permeabilities and those evaluated by the proposed five FMBE methods,indicating the proposed five FMBE methods are effective and rational for CBM reservoirs.Results show that a small amount of free gas will result in a great deviation in reserve evaluation;hence,the immobile free gas expansion effect should be considered when establishing the material balance equation of undersaturated CBM reservoirs at the dewatering stage.

The status and development strategy of coalbed methane industry in China

To achieve the goals of carbon peaking and carbon neutrality under the backgrounds of poor resource endowments, weak theoretical basis and other factors, the development of the coalbed methane industry of China faces many bottlenecks and challenges. This paper systematically analyzes the coalbed methane resources, key technologies and progress, exploration effect and production performance in China and abroad. The main problems are summarized as low exploration degree, low technical adaptability, low return on investment and small development scale. This study suggests that the coalbed methane industry in China should follow the “two-step”(short-term and long-term) development strategy. The short-term action before 2030, can be divided into two stages:(1) From the present to 2025, to achieve new breakthroughs in theory and technology, and accomplish the target of annual production of 10 billion cubic meters;(2) From 2025 to 2030, to form the technologies suitable for most geological conditions, further expand the industry scale, and achieve an annual output of 30 billion cubic meters, improving the proportion of coalbed methane in the total natural gas production. The long-term action after 2030 is to gradually realize an annual production of 100 billion cubic meters. The strategic countermeasure to achieve the above goals is to adhere to “technology+management dual wheel drive”, realize the synchronous progress of technology and management, and promote the high-quality development of the coalbed methane industry. Technically, the efforts will focus on fine and effective development of coalbed methane in the medium to shallow layers of mature fields, effective development of coalbed methane in new fields, extensive and beneficial development of deep coalbed methane, three-dimensional comingled development of coalbed methane, applying new technologies such as coalbed methane displacement by carbon dioxide, microwave heating and stimulation technology, ultrasonic stimulation, high-temperature heat injection stimulation, rock breaking by high-energy laser. In terms of management, the efforts will focus on coordinative innovation of resource, technology, talent, policy and investment, with technological innovation as the core, to realize an all-round and integrated management and promote the development of coalbed methane industry at a high level.

Development unit division and favorable area evaluation for joint mining coalbed methane

Based on the productivity equation of coalbed methane (CBM) well, considering the impact of coal reservoir reformability on gas well productivity, the main production layer optimization index in the “three-step method” of optimal combination of production layers is corrected, and then the CBM production layer potential index is introduced to evaluate favorable areas for commingled multi-coal seam production. Through analysis of the key parameters of coal reservoirs affecting the CBM productivity index, a development unit division method for areas with multi-coal seams is established, and a quantitative grading index system is proposed. On this basis, the evaluation process of CBM development favorable area is developed: the mature 3-D modeling technology is used to characterize the reservoir physical properties of multi-coal seams in full-scale;the production layer potential index of each grid is calculated, and the production layer potential index contour under single-layer or commingled multi-layer production are plotted;according to the distribution of the contour of production layer potential index, the quantitative index of CBM development unit is adopted to outline the grade I, II, III coal reservoir distribution areas, and thus to pick out the favorable development areas. The practical application in the Yuwang block of Laochang in Yunnan proved that the favorable area evaluation process proposed can effectively overcome the defects of selecting favorable development areas only relying on evaluation results of a major coal seam pay, and enhance the accuracy of the evaluation results, meeting the requirements of selecting favorable areas for multi-coal seam commingled CBM production.

High rank coalbed methane desorption characteristic and its application in production in Qinshui basin

Based on spontaneous desorption characteristic, the correlation of desorption time and gas content was analyzed and the application of it in production was researched. The desorption of high rank coalbed methane in Qinshui basin was periodic, and isotope fractionation effect also exists in the process. △δ^13C1 can be used to distinguish the stabilization of coalbed methane wells, associated with desorption rate, the individual well recoverable reserves can be calculated. Economically recoverable time can be predicted according to the logarithmic relationship between desorption gas content per ton and desorption time. The error between predicted result and numerical simulation result is only 1.5%.

Numerical well test for well with finite conductivity vertical fracture in coalbed

A new well test model is developed for the hydraulic fractured well in coalbed by considering the following aspects： methane desorption phenomena, finite conductivity vertical fractures, and asymmetry of the fracture about the well. A new parameter is introduced to describe the storage of the fracture, which is named as a combined fracture storage. Another new concept called the fracture asymmetry coefficient is used to define the asymmetry of the fracture about the well. Finite element method （FEM） is used to solve the new mathematical model. The well test type curves and pressure fields are obtained and analyzed. The effects of the combined fracture storage, desorption factor, fracture conductivity, and fracture asymmetry coefficient on the well test type curves are discussed in detail. In order to verify the new model, a set of field well test data is analyzed.

BiOBr nanosheets coupling with biomass carbon derived from locust leaves for enhanced photocatalytic degradation of rhodamine B

A series of BiOBr@biomass carbon derived from locust leaves materials(BiOBr@BC)were fabricated and the photocatalytic property was investigated for photocatalytic degradation of rhodamine B(RhB)under visible light.The morphology,structure and photoelectrochemical properties of the photocatalysts were characterized by means of SEM,TEM,XRD,XPS,FT-IR,BET,PL,UV-vis/DRS,and EIS techniques.The results showed that the introduction of BC significantly enhanced the photocatalytic activity.When the content of biomass carbon(BC)in a composite is 3%(based on the mass of BiOBr),the obtained BiOBr@BC-3 exhibits excellent photocatalytic activity,degrading 99%of RhB within 20 min.The excellent degradation efficiency after the introduction of BC can be attributed to the enhanced visible light absorption,narrower band gap,and fast electron-hole pair separation rate.The photocatalytic mechanism on the degradation of RhB was illustrated based on the radicals'trapping experiments and semiconductor energy band position.The proposed material is expected to be of significant application value in the field of wastewater treatment.

Coal-rock gas:Concept,connotation and classification criteria

In recent years,great breakthroughs have been made in the exploration and development of natural gas in deep coal-rock reservoirs in Junggar,Ordos and other basins in China.In view of the inconsistency between the industrial and academic circles on this new type of unconventional natural gas,this paper defines the concept of"coal-rock gas"on the basis of previous studies,and systematically analyzes its characteristics of occurrence state,transport and storage form,differential accumulation,and development law.Coal-rock gas,geologically unlike coalbed methane in the traditional sense,occurs in both free and adsorbed states,with free state in abundance.It is generated and stored in the same set of rocks through short distance migration,occasionally with the accumulation from other sources.Moreover,coal rock develops cleat fractures,and the free gas accumulates differentially.The coal-rock gas reservoirs deeper than 2000 m are high in pressure,temperature,gas content,gas saturation,and free-gas content.In terms of development,similar to shale gas and tight gas,coal-rock gas can be exploited by natural formation energy after the reservoirs connectivity is improved artificially,that is,the adsorbed gas is desorbed due to pressure drop after the high-potential free gas is recovered,so that the free gas and adsorbed gas are produced in succession for a long term without water drainage for pressure drop.According to buried depth,coal rank,pressure coefficient,reserves scale,reserves abundance and gas well production,the classification criteria and reserves/resources estimation method of coal-rock gas are presented.It is preliminarily estimated that the coal-rock gas in place deeper than 2000 m in China exceeds 30×10^(12)m^(3),indicating an important strategic resource for the country.The Ordos,Sichuan,Junggar and Bohai Bay basins are favorable areas for large-scale enrichment of coal-rock gas.The paper summarizes the technical and management challenges and points out the research directions,laying a foundation for the management,exploration,and development of coal-rock gas in China.

Paleoenvironment of marine-continental transitional shales in the lower Permian Shanxi formation,southeastern Ordos Basin,China

The paleoenvironment of shales can be reconstructed to some extent using the combinations or concentrations of elements that correlate strongly with environmental conditions.In this study,we analyzed rare earth elements(REEs),major elements,and trace elements in the marine-continental transitional shales(transitional shales for short)of the Shan 2^(3)submember of the Shanxi Formation in the southeastern Ordos Basin.The purpose is to deduce the paleoenvironmental conditions of the shales,encompassing paleoredox,paleoclimate,paleoproductivity,and paleo-provenance.The Shan 2^(3)submember comprises four sections,namely Shan 2^(3)-1,Shan 2^(3)-2,Shan 2^(3)-3,and Shan 2^(3)-4.The Ba/Al,P/Al,and Cu/Al ratios,along with biogenic barium(Babio),indicate that the paleoproductivity of the submember peaked during the Shan 2^(3)-1 deposition and exhibited a downtrend upward in other sections.Trends in the Uau and the Ni/Co,V/Cr,U/Th,and V/Sc ratios suggest that suboxic conditions prevailed during the Shan 2^(3)-1 deposition,with the oxidation level gradually increasing from Shan 2^(3)-1 to Shan 2^(3)-4.C-value and the Sr/Cu vs.Ga/Rb cross-plot indicate a warm and arid paleoclimate during the Shan 2^(3)-1 deposition,which transitioned to cooler,drier conditions during the deposition of other sections.Indicators sensitive to paleoclimate,such as the K/Rb and Th/U ratios,along with the ICV,PIA,and Chemical Index of Alteration(CIA),highlight elevated weathering from Shan 2^(3)-2 to Shan 2^(3)-4,with Shan 2^(3)-1 exhibiting the weakest weathering during its deposition.As suggested by the REE data,the Zr/Sc vs.Th/Sr cross-plot,provenance discriminant functions,and the cross-plots of Hf vs.La/Th,Th vs.Hf-Co,and∑REE vs.La/Yb,the sedimentary provenance for the transitional shales of the Shan 2^(3)submember is of multiple origins,with significant contributions from the Upper Continental Crust(UCC).Discriminant diagrams,including those of Th-Co-Zr/10,Th-Sc-Zr/10,La-Th-Sc,and K_(2)O/Na_(2)O vs.SiO_(2),suggest that the transitional shales of the Shan 2^(3)submember were primarily deposited under tectonic settings such as continental island arcs(CIAs)and passive continental margins(PCMs).

Favorable lithofacies types and genesis of marine- continental transitional black shale: A case study of Permian Shanxi Formation in the eastern margin of Ordos Basin, NW China

Based on core description,thin section identification,X-ray diffraction analysis,scanning electron microscopy,low-temperature gas adsorption and high-pressure mercury intrusion porosimetry,the shale lithofacies of Shan23 sub-member of Permian Shanxi Formation in the east margin of Ordos Basin was systematically analyzed in this study.The Shan23 sub-member has six lithofacies,namely,low TOC clay shale(C-L),low TOC siliceous shale(S-L),medium TOC siliceous shale(S-M),medium TOC hybrid shale(M-M),high TOC siliceous shale(S-H),and high TOC clay shale(C-H).Among them,S-H is the best lithofacies,S-M and M-M are the second best.The C-L and C-H lithofacies,mainly found in the upper part of Shan23 sub-member,generally developed in tide-dominated delta facies;the S-L,S-M,S-H and M-M shales occurring in the lower part of Shan23 sub-member developed in tide-dominated estuarine bay facies.The S-H,S-M and M-M shales have good pore struc-ture and largely organic matter pores and mineral interparticle pores,including interlayer pore in clay minerals,pyrite inter-crystalline pore,and mineral dissolution pore.C-L and S-L shales have mainly mineral interparticle pores and clay mineral in-terlayer pores,and a small amount of organic matter pores,showing poorer pore structure.The C-H shale has organic mi-cro-pores and a small number of interlayer fissures of clay minerals,showing good micro-pore structure,and poor meso-pore and macro-pore structure.The formation of favorable lithofacies is jointly controlled by depositional environment and diagen-esis.Shallow bay-lagoon depositional environment is conducive to the formation of type II2 kerogen which can produce a large number of organic cellular pores.Besides,the rich biogenic silica is conducive to the preservation of primary pores and en-hances the fracability of the shale reservoir.

Dynamic characteristics and influencing factors of CO_(2) huff and puff in tight oil reservoirs

CO_(2)huff and puff experiments of different injection parameters,production parameters and soaking time were carried out on large-scale cubic and long columnar outcrop samples to analyze dynamic characteristics and influencing factors of CO_(2)huff and puff and the contribution of sweeping mode to recovery.The experimental results show that the development process of CO_(2)huff and puff can be divided into four stages,namely,CO_(2)backflow,production of gas with some oil,high-speed oil production,and oil production rate decline stages.The production of gas with some oil stage is dominated by free gas displacement,and the high-speed oil production stage is dominated by dissolved gas displacement.CO_(2)injection volume and development speed are the major factors affecting the oil recovery.The larger the injected CO_(2)volume and the lower the development speed,the higher the oil recovery will be.The reasonable CO_(2)injection volume and development speed should be worked out according to oilfield demand and economic evaluation.There is a reasonable soaking time in CO_(2)huff and puff.Longer soaking time than the optimum time makes little contribution to oil recovery.In field applications,the stability of bottom hole pressure is important to judge whether the soaking time is sufficient during the huff period.The oil recovery of CO_(2)huff and puff mainly comes from the contribution of flow sweep and diffusion sweep,and diffusion sweep contributes more to the oil recovery when the soaking time is sufficient.

Impact of formation water on the generation of H2S in condensate reservoirs： a case study from the deep Ordovician in the Tazhong Uplift of the Tarim Basin, NW China

A number of condensate reservoirs with high concentrations of H2S have been discovered in the deep dolomite reservoirs of the lower Ordovician Yingshan Formation（O1y） in the Tazhong Uplift, where the formation water has a high p H value. In the O1y reservoir, the concentrations of Mg^2＋ and SO4^2-in the formation water are higher than those in the upper Ordovician formation.The concentration of H2 S in the condensate reservoirs and the concentration of Mg^2＋in the formation water correlate well in the O1y reservoirs of the Tazhong Uplift, which indicates a presumed thermochemical sulfate reduction（TSR） origin of H2S according to the oxidation theory of contact ion-pairs（CIPs）. Besides, the p H values of the formation water are positively correlated with the concentration of H2S in the condensate reservoirs, which may indicate that high p H might be another factor to promote and maintain TSR. Oil–source correlation of biomarkers in the sulfuretted condensates indicates the Cambrian source rocks could be the origin of condensates. The formation water in the condensate reservoirs of O1y is similar to that in the Cambrian; therefore, the TSR of sulfate-CIPs likelyoccurred in the Cambrian. High H2S-bearing condensates are mainly located near the No. 1 Fault and NE-SW strikeslip faults, which are the major migration pathway of deep fluids in the Tazhong Uplift. The redox between sulfateCIPs and hydrocarbons is the generation mechanism of H2S in the deep dolomite condensate reservoirs of the Tazhong Uplift. This finding should be helpful to predict the fluid properties of deep dolomite reservoirs.

Accumulation of coal-bed gas in the Wangying-Liujia area of the Fuxin basin

The gas enrichment conditions in the Fuxin basin are compared to those of the Powder River basin.The coal bed depth,the gas content,the individual coal bed layer thickness,and the overall structure thickness of the Powder River basin in the U.S.were examined.The main factors affecting gas enrichment were examined.These factors include the coal-forming environment,the gas sources,the geological structure,the presence of magmatic activity,and the local hydrology.The coal-bed gas enrichment area in the Wangying-Liujia block of the Fuxin basin is then discussed by analogy.A hydrodynamic-force/dike-plugging model based on a magma fractured bed is proposed to explain the gas enrichment in this part of the Fuxin basin.High gas production is predicted in areas having similar conditions.This work will aid future coal-bed gas exploration and development.

Advanced production decline analysis of tight gas wells with variable fracture conductivity

Considering the characteristics that the fracture conductivity formed by hydraulic fracturing varies across space and time, a new mathematical model was established for seepage flow in tight gas fractured vertical wells which takes into account the effects of dual variable conductivity and stress sensitivity. The Blasingame advanced production decline curves of the model were obtained using the finite element method with hybrid elements. On this basis, the effects of fracture space and time dual variable conductivity and stress sensitivity on Blasingame curve were analyzed. The study shows that the space variable conductivity mainly reduces decline curve value at the early stage; the time variable conductivity can result in drops of the production and the production integral curves, leading to a S-shaped curve; dual variable conductivity is the superposition of the effects given by the two variable conductivities; both time and space variable conductivities cannot delay the time with which the formation fluid flow reaches the quasi-steady state. The stress sensitivity reduces the curve value gradually rather than sharply, delaying the time the flow reaching the quasi-steady state. Ignoring the effects of variable conductivity and stress sensitivity will not affect the estimation on well controlled dynamic reserves. However, it can result in large errors in the interpretation of fractures and reservoir parameters. Conventional advanced production decline analyses of a tight gas fractured well in the Sulige gas field showed that the new model is more effective and reliable than the conventional model, and thus it can be widely applied in advanced production decline analysis of wells with the same characteristics in other gas fields.

Calculation of dynamic loads of the sucker rod pumping system in CBM wells

The mathematical model of dynamic loads was developed based on an analysis of the polished rod load of beam pumps, and the variation of the dynamic loads and the computation of the minimum and maximum limits during a complete pumping cycle were given out by solving the model.Field examples verify that it is necessary to take into account the inertial and vibration loads while calculating polished rod loads.During the prophase of the pumping production, the dynamic to polished rod load ratio is relatively large.Then the ratio decreases rapidly and becomes small after entering stable production.Moreover, the total deformation of rod and tubing in CBM wells is much smaller than that in oil fields, and the deformation caused by the dynamic loads is also relatively small.The result of this work is the calculation of the dynamic loads.The application of this calculation for the sucker rod pumping system in CBM wells can give the desired accuracy of polished rod load and the dynamometer cards, which provides a reasonable basis for the design and selection of beam pumps.

Characteristics and formation of high quality reservoirs in sediment gravity flows of Gangzhong area,Huanghua depression

Reservoirs can be developed in the sediment gravity flows.However,high quality reservoirs are found widespread in sediment gravity flows of Gangzhong area,Huanghua depression,Bohai Bay Basin,East China.Characteristics and formation of these reservoirs are key problems to be solved.Through comprehensive analysis of thin section petrography,scanning electron microscopy and X-ray diffraction,two distinct rules were obtained.1) These high quality reservoirs have apparent characteristics:lithology consists mainly of medium-fine grained sands; moderately-well sorted and rounded; intergranular pores dominating >70% of the entire pores,surface per unit pore volume reaches 15%; average porosity is 21% and average permeability is 55×10-3 μm2.2) Types of sedimentary microfacies and dissolution strongly control on the formation of high quality reservoirs.Main channels and sandy braided bars have the best reservoir properties.Because that sediments are mainly medium-fine grained sands in high-energy environments.The favorable primary porosity and permeability may promote calcite cementation and help to produce more secondary pores.Besides,at the depth of 2500-3200 m,basically matching threshold of oil generation,organic acid expelled when organic matter became mature,and H+ released during clay mineral transformation.These both result in the dissolution of calcite cements and create large volume pores,then physical properties improve correspondingly.Moreover,deep hydrothermal fluid intrusion may also have impacts on the development of secondary pores.

New progress and future prospects of CBM exploration and development in China

Efforts to speed up China's coal bed methane (CBM) exploration developments related to production safety, optimization of energy structures, prevention of energy waste and reduction of greenhouse gas emissions are all of great significance. In order to strengthen CBM exploration and development in China and to encourage increased growth in the CBM industry, we firstly give a general overview of the recent technological innovations and other developments in CBM exploration in the U.S., Canada and other countries. Using this background information as the starting point, we further present observations and analyses of CBM exploration and development, preferential policies, technical support and implications of R&D for CBM development in China. The results show that the problems related to CBM exploration technology development and lack of a complete set of management policies are still the major issues slowing down the growth of domestic CBM industry. Development of resource exploration and technology, R&D and establishment of favorable government policy to support the industry and the creation of a relevant information platform, etc. are finally recommended.

Geological characteristics and development potential of transitional shale gas in the east margin of the Ordos Basin,NW China

The shales in the 2nd Member of Shanxi formation in the east margin of the Ordos Basin were deposited in a marine-nonmarine transitional environment during the Permian.Based on the recent breakthroughs in the shale gas exploration and theoretical understandings on the shale gas of the study area,with a comparison to marine shale gas in the Sichuan Basin and marine-nonmarine transitional shale gas in the U.S.,this study presents the geological characteristics and development potential of marine-nonmarine transitional gas in the study area.Four geological features are identified in the 2nd Member of the Shanxi Formation in the study area has:(1)stable sedimentary environment is conductive to deposition of widely distributed organic shale;(2)well-developed micro-and nanoscale pore and fracture systems,providing good storage capacity;(3)high content of brittle minerals such as quartz,leading to effectively reservoir fracturing;and(4)moderate reservoir pressure and relatively high gas content,allowing efficient development of shale gas.The 2nd Member of Shanxi Formation in the east margin of Ordos Basin is rich in shale gas resource.Three favorable zones,Yulin-Linxian,Shiloubei-Daning-Jixian,and Hancheng-Huangling are developed,with a total area of 1.28×104 km2 and resources between 1.8×1012 and 2.9×1012m3,indicating a huge exploration potential.Tests of the 2nd Member of Shanxi Formation in vertical wells show that the favorable intervals have stable gas production and high reserves controlled by single well,good recoverability and fracability.This shale interval has sufficient energy,stable production capacity,and good development prospects,as evidenced by systematic well testing.The east margin of the Ordos Basin has several shale intervals in the Shanxi and Taiyuan formations,and several coal seams interbedded,so collaborative production of different types of natural gas in different intervals can be considered.The study results can provide reference for shale gas exploration and development and promote the rapid exploitation of shale gas in China.