In order to obtain a gas seepage law of deep mined coal seams, according to the properties of coalbed methane seepage in in-situ stress and geothermal temperature fields, the gas seepage equation of deep mined coal se...In order to obtain a gas seepage law of deep mined coal seams, according to the properties of coalbed methane seepage in in-situ stress and geothermal temperature fields, the gas seepage equation of deep mined coal seams with the Klinkenberg effect was obtained by confirming the coatbed methane permeability in in-situ stress and geothermal temperature fields. Aimed at the condition in which the coal seams have or do not have an outcrop and outlet on the ground, the application of the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields on the gas pressure calculation of deep mined coal seams was investigated. The comparison between calculated and measured results indicates that the calculation method of gas pressure, based on the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields can accu- rately be identical with the measured values and theoretically perfect the calculation method of gas pressure of deep mined coal seams.展开更多
In underground engineering,such as geological CO2 sequestration,unconventional oil and gas exploration,and radioactive waste storage,permeability of rock is important to evaluate the potential CO2 storage capacity,imp...In underground engineering,such as geological CO2 sequestration,unconventional oil and gas exploration,and radioactive waste storage,permeability of rock is important to evaluate the potential CO2 storage capacity,improve oil and gas production,and prevent leakage of radioactive waste.In this study,hydrostatic stress tests and triaxial compression tests with gas permeability measurements were carried out on intact and damaged sandstone specimens.Three series of experiment were designed to evaluate the permeability evolution laws of sandstone under different testing conditions.They included triaxial seepage tests on intact specimens under different confining pressures,triaxial seepage tests on damaged specimens with different extents of damage,and hydrostatic seepage tests on damaged specimens under increasing and decreasing gas pressures.Based on the experimental results,the effects of effective confining pressure,extent of damage and increasing and decreasing gas pressure on permeability of sandstone were investigated.It shows that the permeability of the intact sandstone specimens first decreased and then increased,followed by a constant value with increase in axial strain.The permeability of the sandstone specimens was observed to decrease with increase in effective confining pressure.The extent of damage affects the permeability evolution,but does not influence the failure patterns of damaged sandstone.As the gas pressure increased,the permeability of the damaged sandstone specimen increased.Under the same gas pressure condition,the permeability during the decreasing process is generally higher than that during the increasing process.These experiments are expected to enhance our understanding of seepage behavior in underground rock masses.展开更多
To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom s...To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation: to help gather enough methane into a small area and to modulate the thermal regime.展开更多
The seepage evolution characteristic of brittle rock materials is very significant for the stability and safety of rock engineering. In this research, a series of conventional triaxial compression and gas seepage test...The seepage evolution characteristic of brittle rock materials is very significant for the stability and safety of rock engineering. In this research, a series of conventional triaxial compression and gas seepage tests were carded out on sandstone specimens with a rock mechanics servo-controlled testing system. Based on the experimental results, the relationship between permeability and deformation is firstly analyzed in detail. The results show that the permeabilityaxial strain curve can be divided into the following five phases: the phase of micro-defects closure, the phase of linear elastic deformation, the phase of nonlinear deformation, the phase of post-peak stress softening and the phase of residual strength. The seepage evolution characteristic is also closely correlated with the volumetric deformation according to the relationship between permeability and volumetric strain. It is found that the gas seepage pressure has a great effect on the permeability evolution, i.e. permeability coefficients increase with increasing gas seepage pressures. Finally, the influence of gas seepage pressures on the failure behavior of brittle sandstone specimens is discussed.展开更多
Tight sandstone gas(hereafter"tight gas")has become a subject of unconventional gas exploration globally.The large-scale development and use of tight gas resources in the USA,in particular,facilitated the ra...Tight sandstone gas(hereafter"tight gas")has become a subject of unconventional gas exploration globally.The large-scale development and use of tight gas resources in the USA,in particular,facilitated the rapid rebound of natural gas production in the USA,in addition to driving the rapid development of tight gas worldwide.In the eastern Ordos Basin,the Upper Paleozoic feature includes multiple layers of gas,a shallow depth,and notable potential for exploration and development.However,the reservoirs in the area are relatively tight,exhibit strong heterogeneity,and possess a complex micropore structure,thus restricting the eff ective economic development of oil and gas.Thus,research on the primary parameters controlling pore throat structure and the seepage capability of low-permeability reservoirs will be beneficial for the effcient exploration and development of natural gas in the eastern Ordos Basin.The parameters of reservoir porosity and percolation ability,as well as permeability,were analyzed using systematic sampling of the of the Upper Paleozoic Benxi,Taiyuan,and Shanxi Formations in the eastern Ordos Basin,constant-rate mercury injection experiments,nuclear magnetic resonance analysis,and gas–water-phase experimental studies.The results indicate that reservoir porosity is controlled by the effective pore volume and number,whereas permeability is controlled by the largest throat radius,rather than the average.The effective pore volume controls the movable fluid saturation,while reservoir percolation capability is controlled by the effective pore volume,irreducible water saturation,and size of the gas–water two-phase seepage zone.展开更多
Dynamics of gas seepage as a borderline subject of geosciences mainly studies the flow and distribution of gas in coalseams or gas-bearing strata. In this paper new dynamic models for coal gas flow are developed.Using...Dynamics of gas seepage as a borderline subject of geosciences mainly studies the flow and distribution of gas in coalseams or gas-bearing strata. In this paper new dynamic models for coal gas flow are developed.Using in-situ measured parameters of coal gas dynamics, the new models are tested with three existing dynamic models in the world. The results show that the new models approach the reality more cIose than the other three models.In addition, the other relations or indices helped to evaluate gas flow in coalseam are proposed.展开更多
A gas–solid coupling model involving coal seam deformation,gas diffusion and seepage,gas adsorption and desorption was built to study the gas transport rule under the effect of protective coal seam mining.The researc...A gas–solid coupling model involving coal seam deformation,gas diffusion and seepage,gas adsorption and desorption was built to study the gas transport rule under the effect of protective coal seam mining.The research results indicate:(1) The depressurization effect changes the stress state of an overlying coal seam and causes its permeability to increase,thus gas in the protected coal seam will be desorbed and transported under the effect of a gas pressure gradient,which will cause a decrease in gas pressure.(2) Gas pressure can be further decreased by setting out gas extraction boreholes in the overlying coal seam,which can effectively reduce the coal and gas outburst risk.The research is of important engineering significance for studying the gas transport rule in protected coal seam and providing important reference for controlling coal and gas outbursts in deep mining in China.展开更多
According to the cover rock caving features,the gob of fully mechanized caving face was divided into 3 zones: natural collected zone,pressure effecting zone and press stable zone.Based on these and the gob gas flow co...According to the cover rock caving features,the gob of fully mechanized caving face was divided into 3 zones: natural collected zone,pressure effecting zone and press stable zone.Based on these and the gob gas flow control equation,and considered the in- fluence to the mining fissured zone of gas drainage,also made use of CFD software,we found an not uniform 3D numerical model of gob gas seepage and got the gas emission law in gob of fully mechanized caving face (with or without discharge measures),and this can guide the engineering practice in some aspects.展开更多
Great advancement has been made on natural gas hydrates exploration and test production in the northern South China Sea.However,there remains a lot of key questions yet to be resolved,particularly about the mechanisms...Great advancement has been made on natural gas hydrates exploration and test production in the northern South China Sea.However,there remains a lot of key questions yet to be resolved,particularly about the mechanisms and the controls of gas hydrates enrichment.Numerical simulaution would play signficant role in addressing these questions.This study focused on the gas hydrate exploration in the Shenhu Area,Northern South China Sea.Based on the newly obtained borehole and multichannel reflection seismic data,the authors conducted an integrated 3D basin modeling study on gas hydrate.The results indicate that the Shenhu Area has favorable conditions for gas hydrate accumulation,such as temperature,pressure,hydrocarbon source,and tectonic setting.Gas hydrates are most concentrated in the Late Miocene strata,particularly in the structual highs between the Baiyun Sag and the Liwan Sag,and area to the south of it.It also proved the existence of overpressure in the main sag of source rocks,which was subject to compaction disequilibrium and hydrocarbon generation.It also shown that the regional fault activity is not conducive to gas hydrate accumulation due to excess gas seepage.The authors conjecture that fault activity may slightly weaken overpressure for the positive effect of hydrocarbon expulsion and areas lacking regional fault activity have better potential.展开更多
基金support of the Open Fund of State Key Laboratory of Oil and Gas Reser-voir Geology and Exploitation (Southwest Petroleum University) (PLN0610)the Opening Project of He-nan Key Laboratory of Coal Mine Methane and Fire Prevention (HKLGF200706)+3 种基金 the National Natural Science Foundation of China (No. 50334060, 50474025, 50774106)the National Key Fundamental Research and Development Program of China (No. 2005CB221502)the Natural Science Innovation Group Foundation of China (No. 50621403)the Natural Science Foundation of Chongqing of China(No. CSTC, 2006BB7147, 2006AA7002).
文摘In order to obtain a gas seepage law of deep mined coal seams, according to the properties of coalbed methane seepage in in-situ stress and geothermal temperature fields, the gas seepage equation of deep mined coal seams with the Klinkenberg effect was obtained by confirming the coatbed methane permeability in in-situ stress and geothermal temperature fields. Aimed at the condition in which the coal seams have or do not have an outcrop and outlet on the ground, the application of the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields on the gas pressure calculation of deep mined coal seams was investigated. The comparison between calculated and measured results indicates that the calculation method of gas pressure, based on the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields can accu- rately be identical with the measured values and theoretically perfect the calculation method of gas pressure of deep mined coal seams.
基金supported by the National Natural Science Foundation of China(Grant Nos.41272344 and 51909260)the Fundamental Research Funds for the Central Universities(Grant No.2020ZDPYMS34)。
文摘In underground engineering,such as geological CO2 sequestration,unconventional oil and gas exploration,and radioactive waste storage,permeability of rock is important to evaluate the potential CO2 storage capacity,improve oil and gas production,and prevent leakage of radioactive waste.In this study,hydrostatic stress tests and triaxial compression tests with gas permeability measurements were carried out on intact and damaged sandstone specimens.Three series of experiment were designed to evaluate the permeability evolution laws of sandstone under different testing conditions.They included triaxial seepage tests on intact specimens under different confining pressures,triaxial seepage tests on damaged specimens with different extents of damage,and hydrostatic seepage tests on damaged specimens under increasing and decreasing gas pressures.Based on the experimental results,the effects of effective confining pressure,extent of damage and increasing and decreasing gas pressure on permeability of sandstone were investigated.It shows that the permeability of the intact sandstone specimens first decreased and then increased,followed by a constant value with increase in axial strain.The permeability of the sandstone specimens was observed to decrease with increase in effective confining pressure.The extent of damage affects the permeability evolution,but does not influence the failure patterns of damaged sandstone.As the gas pressure increased,the permeability of the damaged sandstone specimen increased.Under the same gas pressure condition,the permeability during the decreasing process is generally higher than that during the increasing process.These experiments are expected to enhance our understanding of seepage behavior in underground rock masses.
基金the National Natural Science Foundation of China (No.40776032)Key Discipline Program of Chinese Academy of Sciences (No.KZCX2-211-01)National Basic Research Program of China (973 Program,No.207CB411702)
文摘To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation: to help gather enough methane into a small area and to modulate the thermal regime.
基金supported by the National Natural Science Foundation of China (Grant 41272344)the National Basic Research Program (973) of China (Grant 2014CB046905)+3 种基金the Natural Science Foundation of Jiangsu Province of China (Grant BK2012568)the Team Project Funded by 2014 Jiangsu Innovation and Entrepreneurship Programthe Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grants 2014YC10 and 2014XT03)Outstanding Innovation Team Project in China University of Mining and Technology (Grant 2014QN002)
文摘The seepage evolution characteristic of brittle rock materials is very significant for the stability and safety of rock engineering. In this research, a series of conventional triaxial compression and gas seepage tests were carded out on sandstone specimens with a rock mechanics servo-controlled testing system. Based on the experimental results, the relationship between permeability and deformation is firstly analyzed in detail. The results show that the permeabilityaxial strain curve can be divided into the following five phases: the phase of micro-defects closure, the phase of linear elastic deformation, the phase of nonlinear deformation, the phase of post-peak stress softening and the phase of residual strength. The seepage evolution characteristic is also closely correlated with the volumetric deformation according to the relationship between permeability and volumetric strain. It is found that the gas seepage pressure has a great effect on the permeability evolution, i.e. permeability coefficients increase with increasing gas seepage pressures. Finally, the influence of gas seepage pressures on the failure behavior of brittle sandstone specimens is discussed.
基金supported by the National Natural Science Foundation of China(Grants Nos.41390451 and 41172101)the National Key Research Project of China(No.2016YFC0601003)
文摘Tight sandstone gas(hereafter"tight gas")has become a subject of unconventional gas exploration globally.The large-scale development and use of tight gas resources in the USA,in particular,facilitated the rapid rebound of natural gas production in the USA,in addition to driving the rapid development of tight gas worldwide.In the eastern Ordos Basin,the Upper Paleozoic feature includes multiple layers of gas,a shallow depth,and notable potential for exploration and development.However,the reservoirs in the area are relatively tight,exhibit strong heterogeneity,and possess a complex micropore structure,thus restricting the eff ective economic development of oil and gas.Thus,research on the primary parameters controlling pore throat structure and the seepage capability of low-permeability reservoirs will be beneficial for the effcient exploration and development of natural gas in the eastern Ordos Basin.The parameters of reservoir porosity and percolation ability,as well as permeability,were analyzed using systematic sampling of the of the Upper Paleozoic Benxi,Taiyuan,and Shanxi Formations in the eastern Ordos Basin,constant-rate mercury injection experiments,nuclear magnetic resonance analysis,and gas–water-phase experimental studies.The results indicate that reservoir porosity is controlled by the effective pore volume and number,whereas permeability is controlled by the largest throat radius,rather than the average.The effective pore volume controls the movable fluid saturation,while reservoir percolation capability is controlled by the effective pore volume,irreducible water saturation,and size of the gas–water two-phase seepage zone.
文摘Dynamics of gas seepage as a borderline subject of geosciences mainly studies the flow and distribution of gas in coalseams or gas-bearing strata. In this paper new dynamic models for coal gas flow are developed.Using in-situ measured parameters of coal gas dynamics, the new models are tested with three existing dynamic models in the world. The results show that the new models approach the reality more cIose than the other three models.In addition, the other relations or indices helped to evaluate gas flow in coalseam are proposed.
基金supported by the National Natural Science Foundation of China (Nos.51304072,51574112 and 51404100)the Excellent Youth Foundation of Henan Scientific Committee (No.164100510013)+2 种基金the Key Scientific Research Project of Colleges and Universities of Henan Province (No.15A440010)the Chinese Ministry of Education Science and Technology Research Project (No.213022A)the Doctoral Foundation of Henan Polytechnic University (No.B2013-007)
文摘A gas–solid coupling model involving coal seam deformation,gas diffusion and seepage,gas adsorption and desorption was built to study the gas transport rule under the effect of protective coal seam mining.The research results indicate:(1) The depressurization effect changes the stress state of an overlying coal seam and causes its permeability to increase,thus gas in the protected coal seam will be desorbed and transported under the effect of a gas pressure gradient,which will cause a decrease in gas pressure.(2) Gas pressure can be further decreased by setting out gas extraction boreholes in the overlying coal seam,which can effectively reduce the coal and gas outburst risk.The research is of important engineering significance for studying the gas transport rule in protected coal seam and providing important reference for controlling coal and gas outbursts in deep mining in China.
基金the National Natural Science Foundation Project of China(505740720)the Natural Science Foundation Project of Shaanxi Province(2006E203)
文摘According to the cover rock caving features,the gob of fully mechanized caving face was divided into 3 zones: natural collected zone,pressure effecting zone and press stable zone.Based on these and the gob gas flow control equation,and considered the in- fluence to the mining fissured zone of gas drainage,also made use of CFD software,we found an not uniform 3D numerical model of gob gas seepage and got the gas emission law in gob of fully mechanized caving face (with or without discharge measures),and this can guide the engineering practice in some aspects.
基金funded by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0201,GML2019ZD0104)Finance Science and Technology Project of Hainan Province(ZDKJ202019).
文摘Great advancement has been made on natural gas hydrates exploration and test production in the northern South China Sea.However,there remains a lot of key questions yet to be resolved,particularly about the mechanisms and the controls of gas hydrates enrichment.Numerical simulaution would play signficant role in addressing these questions.This study focused on the gas hydrate exploration in the Shenhu Area,Northern South China Sea.Based on the newly obtained borehole and multichannel reflection seismic data,the authors conducted an integrated 3D basin modeling study on gas hydrate.The results indicate that the Shenhu Area has favorable conditions for gas hydrate accumulation,such as temperature,pressure,hydrocarbon source,and tectonic setting.Gas hydrates are most concentrated in the Late Miocene strata,particularly in the structual highs between the Baiyun Sag and the Liwan Sag,and area to the south of it.It also proved the existence of overpressure in the main sag of source rocks,which was subject to compaction disequilibrium and hydrocarbon generation.It also shown that the regional fault activity is not conducive to gas hydrate accumulation due to excess gas seepage.The authors conjecture that fault activity may slightly weaken overpressure for the positive effect of hydrocarbon expulsion and areas lacking regional fault activity have better potential.