The knowledge of the residence time of formation water is fundamental to understanding the subsurface flow and hydrological setting.To better identify the origin and evolution of coal seam water and its impact on gas ...The knowledge of the residence time of formation water is fundamental to understanding the subsurface flow and hydrological setting.To better identify the origin and evolution of coal seam water and its impact on gas storage and production,this study collected coalbed methane co-produced water in the southeast Qinshui Basin and detected chemical and isotopic compositions,especially 36Cl and 129I concentrations.The calculated tracer ages of 129I(5.2–50.6 Ma)and 36Cl(0.13–0.76 Ma)are significantly younger than the age of coal-bearing formation(Pennsylvanian-Cisuralian),indicating freshwater recharge after coal deposition.The model that utilises 129I/I and 36Cl/Cl ratios to constrain the timing of recharge and the proportion of recharge water reveals that over 60%of pre-anthropogenic meteoric water entered coal seams since 10 Ma and mixed with residue initial deposition water,corresponding to the basin inversion in Cenozoic.The spatial distribution of major ion concentrations reveals the primary recharge pathway for meteoric water from coal outcrops at the eastern margin to the basin center.This study demonstrates the occurrence of higher gas production rates from wells that accept water recharge in recent times and suggests the possible potential of the non-stagnant zones for high gas production.展开更多
Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and ...Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds.Permanent damage can result if this is not the case,especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output.Current theoretical models and measuring devices are inapplicable to commingled CBM drainage,however,and so large errors in predictive models cannot always be avoided.The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit.A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study.This technique comprises a downhole measurement system combined with a theoretical calculation model.Gas output parameters(i.e.,gas-phase flow rate,temperature,pressure)are measured in this approach via a downhole measurement system;substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit.Trends in gas output from a single well or each seam can therefore be predicted.The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15%and therefore conform with field use requirements.展开更多
Qinshui Basin is located in the southeast of Shanxi Province, China. Taking the shale of Taiyuan Formation in Qinshui Basin as the research object, the study analyzed the pore size of the shale of Taiyuan formation in...Qinshui Basin is located in the southeast of Shanxi Province, China. Taking the shale of Taiyuan Formation in Qinshui Basin as the research object, the study analyzed the pore size of the shale of Taiyuan formation in detail from micropore to macropore by the methods of mercury injection, liquid nitrogen analysis and combination of liquid nitrogen and mercury injection. The results show that: 1) the visible pores and macropores are poorly developed and distributed unevenly in the shale of Taiyuan formation, and the micropores are well developed in the shale, and there are more open pores in the pore diameter range, and the pore connectivity is good;2) the liquid nitrogen experiment shows that the pores of Taiyuan Shale are relatively developed between 15 nm and 20 nm, and the formation of hysteresis loop may be caused by some narrow slit pores with similar layered structure;3) the comprehensive analysis of liquid nitrogen and mercury injection experiments shows that the shale of the Taiyuan formation mainly develops micropores, the Mesopores is not developed, the pore volume at 10 - 100 nm is more developed than other parts, and the specific surface is mainly contributed by micropores, which can improve the efficiency of shale gas resolution;at the same time, it provides a channel for Shale gas migration, which is beneficial to the development of shale gas.展开更多
Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mech...Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mechanical model was established under the condition of rock mechanics and geostress, and the finite element method was used to simulate the paleotectonic stress field. Based on the Griffith and Mohr-Coulomb criterion, the distribution of tectonic fractures in the Shanxi Formation during the Indosinian, Yanshanian, and Himalayan period can be predicted with the index of comprehensive rupture rate. The results show that the acting force of the Pacific Plate and the India Plate to the North China Plate formed the direction of principal stress is N-S, NW-SE, and NE-SW, respectively, in different periods in the study area. Changes in the direction and strength of the acting force led to the regional gradients of tectonic stress magnitude, which resulted in an asymmetrical distribution state of the stress conditions in different periods. It is suggested that the low-stress areas are mainly located in the fault zones and extend along the direction of the fault zones. Furthermore, the high-stress areas are located in the junction of fold belts and the binding site of multiple folds. The development of tectonic fractures was affected by the distribution of stress intensity and the tectonic position of folds and faults, which resulted in some developed areas with level Ⅰ and Ⅱ. There are obvious differences in the development of tectonic fractures in the fold and fault zones and the anticline and syncline structure at the same fold zones. The tectonic fractures of the Shanxi Formation during the Himalayan period are more developed than those during the Indosinian and Yanshanian period due to the superposition of the late tectonic movement to the early tectonic movement and the differences in the magnitude and direction of stress intensity.展开更多
Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating...Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.展开更多
Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reser...Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.展开更多
Coalbed methane enrichment will be controlled by many good macro geological dynamical conditions; there is evident difference of enrichment grade in different area and different geological conditions.This paper has st...Coalbed methane enrichment will be controlled by many good macro geological dynamical conditions; there is evident difference of enrichment grade in different area and different geological conditions.This paper has studied tectonic dynamical conditions, thermal dynamical conditions and hydraulic conditions, which affect coalbed methane enrichment in Qinshui basin.Coalbed methane enrichment units have been divided based on tectonic dynamical conditions of Qinshui basin,combined with thermal dynamical conditions and hydraulic conditions.展开更多
A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of D...A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.展开更多
As an unconventional natural gas resource,coalbed methane(CBM)development releases a large amount of CBM wells co-produced water.Geochemical characteristics of the co-produced water provide an essential foundation for...As an unconventional natural gas resource,coalbed methane(CBM)development releases a large amount of CBM wells co-produced water.Geochemical characteristics of the co-produced water provide an essential foundation for the production dynamics of CBM reservoirs if the impacts of fracturing fluids and other aquifers can be ignored.In the Shizhuangnan Block of the southern Qinshui Basin,constant and trace elements in CBM co-produced water from the wellheads were collected and determined,which is applied to assess water source,fracturing fluid effect,and CBM production.Based on principle component analysis and hierarchical clustering analysis,the water samples are divided into four categories.It suggests that different characteristics affected by water-rock interaction,reservoir environment,aquifer recharge,and hydraulic fracturing result in the various ratios of Na^(+)/Cl^(-),alkalinity(HCO_(3)^(-)+CO_(3)^(2-))/Cl^(-)and other specific rules.Moreover,Cl^(-)is selected as a dividing line for complete fracturing fluid flow back,associated with organic-bound chlorine complexes in the original coal seam water.Compared to constant elements,there is a significant correlation between Li and Sr concentrations and CBM productivity,so templates regarding trace elements can be used to distinguish various sources of the co-produced water.展开更多
The behavior of coalbed methane(CBM)diffusion considerably influences gas productivity.Based on the multi-porous diffusion model and on-site CBM desorption data of coal cores,the behavior of CBM diffusion and its impl...The behavior of coalbed methane(CBM)diffusion considerably influences gas productivity.Based on the multi-porous diffusion model and on-site CBM desorption data of coal cores,the behavior of CBM diffusion and its implications on the gas productivity of No.3 coal seam in the southern Qinshui Basin(SQB)were elaborately analyzed.Results indicate that CBM diffusion of No.3 coal seam demonstrates noticeable three-stage characteristics,including the fast diffusion,transitional diffusion,and slow diffusion stages.During the gas diffusion process,the gas content and/or the degree of developed pores and fractures/cleats in coal seams can affect the desorption of CBM and the amount of diffused CBM by influencing the changes in gas pressure in pores,thus controlling the behavior of gas diffusion in different stages.Because gas content and the developed degree of pores and fractures/cleats are closely associated with the deformation degree of the coal seams,variably deformed coal seams exhibit unique characteristics of gas diffusion.The low-deformation degree of the coal seams have a relatively uniform distribution of gas production over the history of a well.By contrast,the moderate-deformation degree of the coal seams have a relatively high rate and amount of gas diffusion in the fast and transitional diffusion stages,producing most of the gas in the early-to-intermediate stages of the wells.Finally,the high-deformation degree of the coal seams has a high rate and amount in the fast diffusion stage,indicating that most of the production stage occurs during the early stage of the gas production history of a well.In summary,the behavior of gas diffusion can be used for predicting gas production potential.展开更多
In this study,a group of overmature coal-measure shale core samples was collected in situ from an exploration well located in the Wuxiang area of the Qinshui Basin,north China.The pore water contents(CPW)of the shales...In this study,a group of overmature coal-measure shale core samples was collected in situ from an exploration well located in the Wuxiang area of the Qinshui Basin,north China.The pore water contents(CPW)of the shales under as-received conditions,equilibrium water contents(CEW)of the shales under moisture equilibrium conditions(relative humidity:100%),and nanopore structures of the shales under both as-received and dried conditions were measured.The results indicate that the CPW values of these shales are much lower than their CEW values,which implies that the bulk pore systems of these shales have low water-bearing extents.In addition,approximately half of the total pore volumes and surface areas of the as-received shales are occupied by pore water,and the effects of pore water on shale nanopores with various pore types and widths are different.The average water-occupied percentages(PW)are 59.16%−81.99%and 42.53%−43.44%for the non-micropores and micropores,respectively,and are 83.54%−97.69%and 19.57%−26.42%for the inorganic-matter hosted(IM)and organic-matter hosted(OM)pores,respectively.The pore water in shales not only significantly reduces the storage of shale gas by occupying many pore spaces,but also causes the shale gas,especially the absorbed gas,to be mostly stored in the OM pores;meanwhile,the IM pores mainly store free gas.Therefore,the water-bearing characteristics and their effects on the pore structures and gas-bearing properties of coal-measure shales should be noted for the evaluation and exploration of shale gas in the Qinshui Basin.展开更多
Carbon dioxide(CO_(2))capture,utilization,and storage(CCUS)is an important pathway for China to achieve its“2060 carbon neutrality”strategy.Geological sequestration of CO_(2)in deep coals is one of the methods of CC...Carbon dioxide(CO_(2))capture,utilization,and storage(CCUS)is an important pathway for China to achieve its“2060 carbon neutrality”strategy.Geological sequestration of CO_(2)in deep coals is one of the methods of CCUS.Here,the No.3 anthracite in the Qinshui Basin was studied using the superposition of each CO_(2)geological storage category to construct models for theoretical CO_(2)geological storage capacity(TCGSC)assessment,and CO_(2)adsorption capacity variation with depth.CO_(2)geological storage potential of No.3 anthracite coal was assessed by integrating the adsorption capacity with the static storage and dissolution capacities.The results show that(1)CO_(2)adsorption capacities of XJ and SH coals initially increased with depth,peaked at 47.7 cm3/g and 41.5 cm3/g around 1000 m,and later decreased with depth.(2)four assessment areas and their geological model parameters were established based on CO_(2)phase variation and spatial distribution of coal thickness,(3)the abundance of CO_(2)geological storage capacity(ACGSC),which averages 40 cm3/g,shows an analogous circularity-sharp distribution,with the high abundance area influenced by depth and coal rank,and(4)the TCGSC and the effective CO_(2)geological storage capacity(ECGSC)are 9.72 Gt and 6.54 Gt;the gas subcritical area accounted for 76.41%of the total TCGSC.Although adsorption-related storage capacity accounted for more than 90%of total TCGSC,its proportion,however,decreased with depth.Future CO_(2)-ECBM project should focus on highrank coals in gas subcritical and gas-like supercritical areas.Such research will provide significant reference for assessment of CO_(2)geological storage capacity in deep coals.展开更多
The Qinshui Basin in the southeastern Shanxi Province is an important area for coalbed methane(CBM) exploration and production in China, and recent exploration has revealed the presence of other unconventional types o...The Qinshui Basin in the southeastern Shanxi Province is an important area for coalbed methane(CBM) exploration and production in China, and recent exploration has revealed the presence of other unconventional types of gas such as shale gas and tight sandstone gas. The reservoirs for these unconventional types of gas in this basin are mainly the coals, mudstones, and sandstones of the Carboniferous and Permian; the reservoir thicknesses are controlled by the depositional environments and palaeogeography. This paper presents the results of sedimentological investigations based on data from outcrop and borehole sections, and basin-wide palaeogeographical maps of each formation were reconstructed on the basis of the contours of a variety of lithological parameters. The palaeogeographic units include the depositional environments of the fluvial channel, flood basin(lake), upper delta plain, lower delta plain, delta front, lagoon, tidal flat, barrier bar, and carbonate platform.The Benxi and Taiyuan Formations are composed mainly of limestones, bauxitic mudstones,siltstones, silty mudstones, sandstones, and economically exploitable coal seams, which were formed in delta, tidal flat, lagoon, and carbonate platform environments. The Shanxi Formation consists of sandstones, siltstones, mudstones, and coals; during the deposition of the formation, the northern part of the Qinshui Basin was occupied mainly by an upper delta plain environment, while the central and southern parts were mainly occupied by a lower delta plain environment and the southeastern part by a delta front environment. Thick coal zones occur in the central and southern parts, where the main depositional environment was a lower delta plain. The thick coal zones of the Taiyuan Formation evidently occur in the sandstone-rich belts, located mainly in the lower delta plain environment in the northern part of the basin and the barrier bar environments in the southeastern part of the basin. In contrast, the thick coal zones of the Shanxi Formation extend over the mudstone-rich belts, located in the areas of the lower delta plain environments of the central and southern parts of the Basin.The Xiashihezi, Shangshihezi, and Shiqianfeng Formations consist mainly of red mudstones with thick-interbedded sandstones. During the deposition of these formations, most areas of the basin were occupied by a fluvial channel, resulting in palaeogeographic units that include fluvial channel zones and flood basins. The fluvial channel deposits consist mainly of relatively-thick sandstones, which could have potential for exploration of tight sandstone gas.展开更多
The thermal history of the Qinshui Basin has been studied by using the fission-track analysis of apatite and zircon, integrated analysis of tectonic evolution, magmatic activity and other palaeogeothermal analysis dat...The thermal history of the Qinshui Basin has been studied by using the fission-track analysis of apatite and zircon, integrated analysis of tectonic evolution, magmatic activity and other palaeogeothermal analysis data. Results indicate that the palaeogeothermal gradient between the late-Paleozoic era and the medium-Mesozoic era is relatively low and the palaeogeothermal gradient in the late-Mesozoic is up to 5.56癈/100 m in the middle, and the values are relatively higher in the north and south margins of the basin, reaching over 8.00℃/100 m, which indicates that there was an anomalous tectonic thermal event in the thermal history of Qinshui Basin. This event happened in 110-140 Ma, and the main peak value was between 120 and 140 Ma. This anomalous tectonic thermal event is controlled by the strengthening thermal mobility of the lithosphere and magmatic intrusion. The maturity of the Permo-Carboniferous coal series mainly was controlled by this anomalous thermal field. The apatite fission track date of samples across the basin shows that a rapid tectonic uplifting with cooling existed 26.2-11.5 Ma ago and the upliftings in the north and south of the basin happened earlier than that in the middle. The Permo-Carboniferous strata had been completely annealed in the early 50 Ma, palaeotemperature over 125℃. Since then, especially from Oligocene-Miocene epoch, the strata which experienced large-scale tectonic upliftings with rapid cooling have been kept out of the annealing belt (70-125℃) in a relative low temperature environment. The late Mesozoic tectonic thermal event control hydrocarbon production peak (late Jurassic to early Cretaceous period) of Permo-Carboniferous strata in Qinshui Basin. When the strata experienced upliftings with rapid cooling since Oligocene-Miocene epoch, the hydrocarbon generation of coal series had stopped.展开更多
The Qinshui Basin in China is a major area for exploration and development of high rank coalbed methane. Due to the high rank coal and complicated pore system, no substantial breakthrough in the exploration and develo...The Qinshui Basin in China is a major area for exploration and development of high rank coalbed methane. Due to the high rank coal and complicated pore system, no substantial breakthrough in the exploration and development of coalbed methane has been made until now. Many systematic tests show that a pore system of coal reservoir has some features as follows: the porosity is relatively low; the pore system is dominated by micropores and transition pores; mesopores take the second place, and macropores are nearly absent, which is exceedingly adverse for production of coal-bed methane. However, testing data also revealed the differential development for the pore of high rank coal reservoirs in the Qinshui Basin, which necessarily led to the different physical properties of desorption, diffusion and permeability. This paper classifies the testing data using cluster analysis method and selects the typical samples to establish four pore system models, analyzes the differences of reservoir physical property, and provides a guidance for the exploration and development of coalbed methane in the Qinshui Basin.展开更多
The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermayin...The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermaying Formation (Middle Triassic) is carried by both magnetite and hematite. In stratigraphic coordinates, the direction (Dec = -28°, Inc. =44°, N=10, α95=4°) passes the (incremental) fold test and fabric test. The corresponding paleopole is 64°N, 6° E. The remanent magnetization of samples from the bottom of the Liujiagou Formation (Lower Triassic) is carried mainly by magnetite, which shows an inverse magnetic fabric and an abnormal magnetization direction. This is probably caused by a bedding-parallel compression. A comparison of Triassic paleopoles from this locality with others in North China reveals a significant tectonic rotation of the eastern North China Block and Korean Peninsula with respect to the western North China Block. The rotation probably occurred during the展开更多
Division of CBM (coalbed methane)-enriched units is an important precondition and basic work for formulation of scientific CBM exploration procedure and improvement of CBM exploration success rate. In consideration of...Division of CBM (coalbed methane)-enriched units is an important precondition and basic work for formulation of scientific CBM exploration procedure and improvement of CBM exploration success rate. In consideration of the CBM particularity and complexity as well as its distribution in China, the CBM-enriched units are divided into 5 levels, i.e. CBM-bearing region, CBM-bearing basin, CBM-enriched area, CBM-enriched zone, and CBM reservoir (field). The Qinshui Basin is one of the China’s richest CBM basins with higher exploration degree. However, division and study of CBM-enriched units are relatively weak for the basin. Based on geological conditions of CBM reservoirs formation and current distribution of CBM reservoirs in the Qinshui Basin, this paper divides the basin into 5 CBM-enriched areas, that is, the South Qinshui, Eastern Slope, Western Slope, Xishan, and Gaoping-Jincheng CBM-enriched areas. Of those 5 areas, the South Qinshui is most favorable for CBM exploration.展开更多
The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are me...The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are measured and 20 heat flow values are obtained. The estimated heat flow ranges from 44.75 mW7m2 to 101.81 mW/m2, with a mean of 62.69±15.20 mW/m2. The thermal history reconstruction from the inversion of vitrinite data, using Ther-model for Windows 2004, reveals that the average paleo-heat flow at the time of maximum burial in late Jurassic to early Cretaceous is 158.41 mW/m2 for the north part, 119.57 mW/m2 for the central part and 169.43 mW/m2for the south part of the basin respectively. The reconstruction of the buried history of the strata indicates that the age for the end of sedimentation and the beginning of erosion for the basin is 108-156 Ma, and that the eroded thickness of the strata is 2603 m in the north, 2291 m in the central, and 2528.9 m in the south of the basin respectively. The 'higher in the north and the south, lower in the central' distribution pattern of the paleo-heat flow coincides with the distribution of the coal-bed methane spatially and temporally, which shows that the coal-bed methane is controlled by the paleo-geotem-perature field in the basin.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42150710532 and 42103048).
文摘The knowledge of the residence time of formation water is fundamental to understanding the subsurface flow and hydrological setting.To better identify the origin and evolution of coal seam water and its impact on gas storage and production,this study collected coalbed methane co-produced water in the southeast Qinshui Basin and detected chemical and isotopic compositions,especially 36Cl and 129I concentrations.The calculated tracer ages of 129I(5.2–50.6 Ma)and 36Cl(0.13–0.76 Ma)are significantly younger than the age of coal-bearing formation(Pennsylvanian-Cisuralian),indicating freshwater recharge after coal deposition.The model that utilises 129I/I and 36Cl/Cl ratios to constrain the timing of recharge and the proportion of recharge water reveals that over 60%of pre-anthropogenic meteoric water entered coal seams since 10 Ma and mixed with residue initial deposition water,corresponding to the basin inversion in Cenozoic.The spatial distribution of major ion concentrations reveals the primary recharge pathway for meteoric water from coal outcrops at the eastern margin to the basin center.This study demonstrates the occurrence of higher gas production rates from wells that accept water recharge in recent times and suggests the possible potential of the non-stagnant zones for high gas production.
基金This research was funded by grants from the Natural Science Foundation in Hubei(2018CFB349)the National Natural Sciences Foundation of China(41672155,61733016)Open Research Fund Program of Key Laboratory of Tectonics and Petroleum Resources Ministry of Education(No.TPR-2018-10).
文摘Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds.Permanent damage can result if this is not the case,especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output.Current theoretical models and measuring devices are inapplicable to commingled CBM drainage,however,and so large errors in predictive models cannot always be avoided.The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit.A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study.This technique comprises a downhole measurement system combined with a theoretical calculation model.Gas output parameters(i.e.,gas-phase flow rate,temperature,pressure)are measured in this approach via a downhole measurement system;substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit.Trends in gas output from a single well or each seam can therefore be predicted.The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15%and therefore conform with field use requirements.
文摘Qinshui Basin is located in the southeast of Shanxi Province, China. Taking the shale of Taiyuan Formation in Qinshui Basin as the research object, the study analyzed the pore size of the shale of Taiyuan formation in detail from micropore to macropore by the methods of mercury injection, liquid nitrogen analysis and combination of liquid nitrogen and mercury injection. The results show that: 1) the visible pores and macropores are poorly developed and distributed unevenly in the shale of Taiyuan formation, and the micropores are well developed in the shale, and there are more open pores in the pore diameter range, and the pore connectivity is good;2) the liquid nitrogen experiment shows that the pores of Taiyuan Shale are relatively developed between 15 nm and 20 nm, and the formation of hysteresis loop may be caused by some narrow slit pores with similar layered structure;3) the comprehensive analysis of liquid nitrogen and mercury injection experiments shows that the shale of the Taiyuan formation mainly develops micropores, the Mesopores is not developed, the pore volume at 10 - 100 nm is more developed than other parts, and the specific surface is mainly contributed by micropores, which can improve the efficiency of shale gas resolution;at the same time, it provides a channel for Shale gas migration, which is beneficial to the development of shale gas.
基金financially supported by the National Natural Science Foundation of China (Nos.41402138, 41330635, and 41272154)Key Laboratory of Coal-based CO2 Capture and Geological Storage, Jiangsu Province (China University of Mining and Technology) (No.2016B04)
文摘Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mechanical model was established under the condition of rock mechanics and geostress, and the finite element method was used to simulate the paleotectonic stress field. Based on the Griffith and Mohr-Coulomb criterion, the distribution of tectonic fractures in the Shanxi Formation during the Indosinian, Yanshanian, and Himalayan period can be predicted with the index of comprehensive rupture rate. The results show that the acting force of the Pacific Plate and the India Plate to the North China Plate formed the direction of principal stress is N-S, NW-SE, and NE-SW, respectively, in different periods in the study area. Changes in the direction and strength of the acting force led to the regional gradients of tectonic stress magnitude, which resulted in an asymmetrical distribution state of the stress conditions in different periods. It is suggested that the low-stress areas are mainly located in the fault zones and extend along the direction of the fault zones. Furthermore, the high-stress areas are located in the junction of fold belts and the binding site of multiple folds. The development of tectonic fractures was affected by the distribution of stress intensity and the tectonic position of folds and faults, which resulted in some developed areas with level Ⅰ and Ⅱ. There are obvious differences in the development of tectonic fractures in the fold and fault zones and the anticline and syncline structure at the same fold zones. The tectonic fractures of the Shanxi Formation during the Himalayan period are more developed than those during the Indosinian and Yanshanian period due to the superposition of the late tectonic movement to the early tectonic movement and the differences in the magnitude and direction of stress intensity.
基金financially supported by the Natural Science Foundation of China (No.41802192)the National Science and Technology Key Special Project of China (No.2016ZX05044-002 and No.2016ZX05043)+2 种基金the Shanxi Provincial Basic Research Program-Coal Bed Methane Joint Research Foundation (No.2012012001 and No.2015012014)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (No.SHJT-17-42.18)the Fundamental Research Funds for the Central Universities (No.CUGL170811)
文摘Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.
基金Projects(41330638,41272154)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),ChinaProject(2014M551705)supported by the China Postdoctoral Science Foundation
文摘Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.
文摘Coalbed methane enrichment will be controlled by many good macro geological dynamical conditions; there is evident difference of enrichment grade in different area and different geological conditions.This paper has studied tectonic dynamical conditions, thermal dynamical conditions and hydraulic conditions, which affect coalbed methane enrichment in Qinshui basin.Coalbed methane enrichment units have been divided based on tectonic dynamical conditions of Qinshui basin,combined with thermal dynamical conditions and hydraulic conditions.
基金Supported by the National Natural Science Foundation of China （40972106） the Major Projects of the National Science and Technology of China （2011ZX05042-001-002） the Central Universities Fundamental Research Special Foundation of China （292011266）
基金Supported by the China National Science and Technology Major Project(2017ZX05064)
文摘A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.
基金supported by Open Foundation of the Key Laboratory of Universities in Anhui Province for Prevention of Mine Geological Disasters(No.2022-MGDP-07)National Natural Science Foundation of China(No.42102216)+2 种基金National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum,Beijing(No.PRE/open-2302)the NSFC-Shanxi Coal-Based Low Carbon Joint Fund of China(No.U1910205)National Natural Science Foundations of China(No.41972173)。
文摘As an unconventional natural gas resource,coalbed methane(CBM)development releases a large amount of CBM wells co-produced water.Geochemical characteristics of the co-produced water provide an essential foundation for the production dynamics of CBM reservoirs if the impacts of fracturing fluids and other aquifers can be ignored.In the Shizhuangnan Block of the southern Qinshui Basin,constant and trace elements in CBM co-produced water from the wellheads were collected and determined,which is applied to assess water source,fracturing fluid effect,and CBM production.Based on principle component analysis and hierarchical clustering analysis,the water samples are divided into four categories.It suggests that different characteristics affected by water-rock interaction,reservoir environment,aquifer recharge,and hydraulic fracturing result in the various ratios of Na^(+)/Cl^(-),alkalinity(HCO_(3)^(-)+CO_(3)^(2-))/Cl^(-)and other specific rules.Moreover,Cl^(-)is selected as a dividing line for complete fracturing fluid flow back,associated with organic-bound chlorine complexes in the original coal seam water.Compared to constant elements,there is a significant correlation between Li and Sr concentrations and CBM productivity,so templates regarding trace elements can be used to distinguish various sources of the co-produced water.
基金We acknowledgefinancial support from the National Natural Science Foundation of China(Grant Nos.42125205,41830427,and 42102227).
文摘The behavior of coalbed methane(CBM)diffusion considerably influences gas productivity.Based on the multi-porous diffusion model and on-site CBM desorption data of coal cores,the behavior of CBM diffusion and its implications on the gas productivity of No.3 coal seam in the southern Qinshui Basin(SQB)were elaborately analyzed.Results indicate that CBM diffusion of No.3 coal seam demonstrates noticeable three-stage characteristics,including the fast diffusion,transitional diffusion,and slow diffusion stages.During the gas diffusion process,the gas content and/or the degree of developed pores and fractures/cleats in coal seams can affect the desorption of CBM and the amount of diffused CBM by influencing the changes in gas pressure in pores,thus controlling the behavior of gas diffusion in different stages.Because gas content and the developed degree of pores and fractures/cleats are closely associated with the deformation degree of the coal seams,variably deformed coal seams exhibit unique characteristics of gas diffusion.The low-deformation degree of the coal seams have a relatively uniform distribution of gas production over the history of a well.By contrast,the moderate-deformation degree of the coal seams have a relatively high rate and amount of gas diffusion in the fast and transitional diffusion stages,producing most of the gas in the early-to-intermediate stages of the wells.Finally,the high-deformation degree of the coal seams has a high rate and amount in the fast diffusion stage,indicating that most of the production stage occurs during the early stage of the gas production history of a well.In summary,the behavior of gas diffusion can be used for predicting gas production potential.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.U1810201 and 41925014)the Natural Science Foundation of Guangdong Province(No.2021A1515011381).
文摘In this study,a group of overmature coal-measure shale core samples was collected in situ from an exploration well located in the Wuxiang area of the Qinshui Basin,north China.The pore water contents(CPW)of the shales under as-received conditions,equilibrium water contents(CEW)of the shales under moisture equilibrium conditions(relative humidity:100%),and nanopore structures of the shales under both as-received and dried conditions were measured.The results indicate that the CPW values of these shales are much lower than their CEW values,which implies that the bulk pore systems of these shales have low water-bearing extents.In addition,approximately half of the total pore volumes and surface areas of the as-received shales are occupied by pore water,and the effects of pore water on shale nanopores with various pore types and widths are different.The average water-occupied percentages(PW)are 59.16%−81.99%and 42.53%−43.44%for the non-micropores and micropores,respectively,and are 83.54%−97.69%and 19.57%−26.42%for the inorganic-matter hosted(IM)and organic-matter hosted(OM)pores,respectively.The pore water in shales not only significantly reduces the storage of shale gas by occupying many pore spaces,but also causes the shale gas,especially the absorbed gas,to be mostly stored in the OM pores;meanwhile,the IM pores mainly store free gas.Therefore,the water-bearing characteristics and their effects on the pore structures and gas-bearing properties of coal-measure shales should be noted for the evaluation and exploration of shale gas in the Qinshui Basin.
基金The authors would like to acknowledge the financial support provided by National Natural Science Foundation of China(Nos.42102207,42141012 and 41727801)Major Project supported by Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization,China University of Mining and Technology(2020ZDZZ01C)+1 种基金the Peng Cheng Shang Xue Education Fund of CUMT Education Development Foundation(PCSX202203)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institution(PAPD).
文摘Carbon dioxide(CO_(2))capture,utilization,and storage(CCUS)is an important pathway for China to achieve its“2060 carbon neutrality”strategy.Geological sequestration of CO_(2)in deep coals is one of the methods of CCUS.Here,the No.3 anthracite in the Qinshui Basin was studied using the superposition of each CO_(2)geological storage category to construct models for theoretical CO_(2)geological storage capacity(TCGSC)assessment,and CO_(2)adsorption capacity variation with depth.CO_(2)geological storage potential of No.3 anthracite coal was assessed by integrating the adsorption capacity with the static storage and dissolution capacities.The results show that(1)CO_(2)adsorption capacities of XJ and SH coals initially increased with depth,peaked at 47.7 cm3/g and 41.5 cm3/g around 1000 m,and later decreased with depth.(2)four assessment areas and their geological model parameters were established based on CO_(2)phase variation and spatial distribution of coal thickness,(3)the abundance of CO_(2)geological storage capacity(ACGSC),which averages 40 cm3/g,shows an analogous circularity-sharp distribution,with the high abundance area influenced by depth and coal rank,and(4)the TCGSC and the effective CO_(2)geological storage capacity(ECGSC)are 9.72 Gt and 6.54 Gt;the gas subcritical area accounted for 76.41%of the total TCGSC.Although adsorption-related storage capacity accounted for more than 90%of total TCGSC,its proportion,however,decreased with depth.Future CO_(2)-ECBM project should focus on highrank coals in gas subcritical and gas-like supercritical areas.Such research will provide significant reference for assessment of CO_(2)geological storage capacity in deep coals.
基金supported by the National Natural Science Foundation of China(No.41572090,No.41472131)the Major National S&T(Science and Technology)Program of China(2016ZX05041004-003)
文摘The Qinshui Basin in the southeastern Shanxi Province is an important area for coalbed methane(CBM) exploration and production in China, and recent exploration has revealed the presence of other unconventional types of gas such as shale gas and tight sandstone gas. The reservoirs for these unconventional types of gas in this basin are mainly the coals, mudstones, and sandstones of the Carboniferous and Permian; the reservoir thicknesses are controlled by the depositional environments and palaeogeography. This paper presents the results of sedimentological investigations based on data from outcrop and borehole sections, and basin-wide palaeogeographical maps of each formation were reconstructed on the basis of the contours of a variety of lithological parameters. The palaeogeographic units include the depositional environments of the fluvial channel, flood basin(lake), upper delta plain, lower delta plain, delta front, lagoon, tidal flat, barrier bar, and carbonate platform.The Benxi and Taiyuan Formations are composed mainly of limestones, bauxitic mudstones,siltstones, silty mudstones, sandstones, and economically exploitable coal seams, which were formed in delta, tidal flat, lagoon, and carbonate platform environments. The Shanxi Formation consists of sandstones, siltstones, mudstones, and coals; during the deposition of the formation, the northern part of the Qinshui Basin was occupied mainly by an upper delta plain environment, while the central and southern parts were mainly occupied by a lower delta plain environment and the southeastern part by a delta front environment. Thick coal zones occur in the central and southern parts, where the main depositional environment was a lower delta plain. The thick coal zones of the Taiyuan Formation evidently occur in the sandstone-rich belts, located mainly in the lower delta plain environment in the northern part of the basin and the barrier bar environments in the southeastern part of the basin. In contrast, the thick coal zones of the Shanxi Formation extend over the mudstone-rich belts, located in the areas of the lower delta plain environments of the central and southern parts of the Basin.The Xiashihezi, Shangshihezi, and Shiqianfeng Formations consist mainly of red mudstones with thick-interbedded sandstones. During the deposition of these formations, most areas of the basin were occupied by a fluvial channel, resulting in palaeogeographic units that include fluvial channel zones and flood basins. The fluvial channel deposits consist mainly of relatively-thick sandstones, which could have potential for exploration of tight sandstone gas.
文摘The thermal history of the Qinshui Basin has been studied by using the fission-track analysis of apatite and zircon, integrated analysis of tectonic evolution, magmatic activity and other palaeogeothermal analysis data. Results indicate that the palaeogeothermal gradient between the late-Paleozoic era and the medium-Mesozoic era is relatively low and the palaeogeothermal gradient in the late-Mesozoic is up to 5.56癈/100 m in the middle, and the values are relatively higher in the north and south margins of the basin, reaching over 8.00℃/100 m, which indicates that there was an anomalous tectonic thermal event in the thermal history of Qinshui Basin. This event happened in 110-140 Ma, and the main peak value was between 120 and 140 Ma. This anomalous tectonic thermal event is controlled by the strengthening thermal mobility of the lithosphere and magmatic intrusion. The maturity of the Permo-Carboniferous coal series mainly was controlled by this anomalous thermal field. The apatite fission track date of samples across the basin shows that a rapid tectonic uplifting with cooling existed 26.2-11.5 Ma ago and the upliftings in the north and south of the basin happened earlier than that in the middle. The Permo-Carboniferous strata had been completely annealed in the early 50 Ma, palaeotemperature over 125℃. Since then, especially from Oligocene-Miocene epoch, the strata which experienced large-scale tectonic upliftings with rapid cooling have been kept out of the annealing belt (70-125℃) in a relative low temperature environment. The late Mesozoic tectonic thermal event control hydrocarbon production peak (late Jurassic to early Cretaceous period) of Permo-Carboniferous strata in Qinshui Basin. When the strata experienced upliftings with rapid cooling since Oligocene-Miocene epoch, the hydrocarbon generation of coal series had stopped.
文摘The Qinshui Basin in China is a major area for exploration and development of high rank coalbed methane. Due to the high rank coal and complicated pore system, no substantial breakthrough in the exploration and development of coalbed methane has been made until now. Many systematic tests show that a pore system of coal reservoir has some features as follows: the porosity is relatively low; the pore system is dominated by micropores and transition pores; mesopores take the second place, and macropores are nearly absent, which is exceedingly adverse for production of coal-bed methane. However, testing data also revealed the differential development for the pore of high rank coal reservoirs in the Qinshui Basin, which necessarily led to the different physical properties of desorption, diffusion and permeability. This paper classifies the testing data using cluster analysis method and selects the typical samples to establish four pore system models, analyzes the differences of reservoir physical property, and provides a guidance for the exploration and development of coalbed methane in the Qinshui Basin.
基金Project supported by the National Natural Science Foundation of China.
文摘The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermaying Formation (Middle Triassic) is carried by both magnetite and hematite. In stratigraphic coordinates, the direction (Dec = -28°, Inc. =44°, N=10, α95=4°) passes the (incremental) fold test and fabric test. The corresponding paleopole is 64°N, 6° E. The remanent magnetization of samples from the bottom of the Liujiagou Formation (Lower Triassic) is carried mainly by magnetite, which shows an inverse magnetic fabric and an abnormal magnetization direction. This is probably caused by a bedding-parallel compression. A comparison of Triassic paleopoles from this locality with others in North China reveals a significant tectonic rotation of the eastern North China Block and Korean Peninsula with respect to the western North China Block. The rotation probably occurred during the
文摘Division of CBM (coalbed methane)-enriched units is an important precondition and basic work for formulation of scientific CBM exploration procedure and improvement of CBM exploration success rate. In consideration of the CBM particularity and complexity as well as its distribution in China, the CBM-enriched units are divided into 5 levels, i.e. CBM-bearing region, CBM-bearing basin, CBM-enriched area, CBM-enriched zone, and CBM reservoir (field). The Qinshui Basin is one of the China’s richest CBM basins with higher exploration degree. However, division and study of CBM-enriched units are relatively weak for the basin. Based on geological conditions of CBM reservoirs formation and current distribution of CBM reservoirs in the Qinshui Basin, this paper divides the basin into 5 CBM-enriched areas, that is, the South Qinshui, Eastern Slope, Western Slope, Xishan, and Gaoping-Jincheng CBM-enriched areas. Of those 5 areas, the South Qinshui is most favorable for CBM exploration.
文摘The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are measured and 20 heat flow values are obtained. The estimated heat flow ranges from 44.75 mW7m2 to 101.81 mW/m2, with a mean of 62.69±15.20 mW/m2. The thermal history reconstruction from the inversion of vitrinite data, using Ther-model for Windows 2004, reveals that the average paleo-heat flow at the time of maximum burial in late Jurassic to early Cretaceous is 158.41 mW/m2 for the north part, 119.57 mW/m2 for the central part and 169.43 mW/m2for the south part of the basin respectively. The reconstruction of the buried history of the strata indicates that the age for the end of sedimentation and the beginning of erosion for the basin is 108-156 Ma, and that the eroded thickness of the strata is 2603 m in the north, 2291 m in the central, and 2528.9 m in the south of the basin respectively. The 'higher in the north and the south, lower in the central' distribution pattern of the paleo-heat flow coincides with the distribution of the coal-bed methane spatially and temporally, which shows that the coal-bed methane is controlled by the paleo-geotem-perature field in the basin.
