The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.T...The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.The dynamic sealing capacity of a caprock-fault system is a critical constraint for safe operation,and is a key factor in determining the maximum operating pressure(MOP).This study proposed an efficient semi-analytical method for calculating changes in the in situ stress within the caprock.Next,the parameters of dynamic pore pressure,in situ stresses,and deformations obtained from reservoir simulations and geomechanical modeling were used for inputs for the analytical solution.Based on the calculated results,an experimental scheme for the coupled cyclic stress-permeability testing of caprock was designed.The stability analysis indicated that the caprock was not prone to fatigue shear failure under the current injection and production strategy,supported by the experimental results.The experimental results further reveal that the sealing capacity of caprock plugs may remain stable.This phenomenon is attributed to cyclic stress causing pore connectivity and microcrack initiation in certain plugs,while leading to pore compaction in others.A comparison between the dynamic pore pressure and the minimum principal stress suggests that the risk of tensile failure is extremely low.Furthermore,although the faults remain stable under the current injection and production strategies,the continuous increase in injection pressure may lead to an increased tendency for fault slip and dilation,which can cause fault slip ultimately.The MOPs corresponding to each failure mode were calculated.The minimum value of approximately 36.5 MPa at capillary sealing failure indicated that the gas breakthrough in the caprock occurred earlier than rock failure.Therefore,this minimumvalue can be used as the MOP for the target UGS.展开更多
Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulat...Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal,and alternating loads.This study detailed the methodology developed by Sinopec.The approach merges disciplines like geology,geomechanics,and hydrodynamics,employing both dynamic-static and qualitative-quantitative analyses.Sinopec's evaluation methods,grounded in the in situ stress analysis,include mechanistic studies,laboratory tests,geological surveys,stress analysis,and fluid-solid interactions.Through tests on the static and dynamic sealing capacity of UGS,alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults,A geomechanics-rock damage-seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity,thereby setting the maximum operational pressures.Utilizing this evaluation technique,Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs,enabling preliminary sealing capacity evaluations at UGS sites.These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.展开更多
In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the op...In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the operation safety of gas storages,this paper takes Xinjiang H gas storage whose storage capacity and peak shaving capacity are the highest in China as the research object to establish a 3D fine geological model and a 3D dynamic geomechanical model in the regional scale of H gas storage based on the alternating change characteristics of geostress field during the high-speed cyclic injection and production of gas storage,combined with the geological,seismic,logging and various laboratory core experiment results.Then,the trap dynamic sealing capacity of H gas storage under the action of alternating stress after 14 years of depletion development of its original gas reservoir and long-term high-speed injection and production after its reconstruction from the gas reservoir was evaluated comprehensively.And the following research results were obtained.First,the change of the formation pressure in H gas storage has a significant effect on the regional geostress field.Second,after the development of the original H gas reservoir,the geostress on the two sides of the fault are greatly different,but the cap rock is not deformed and failed and the reservoir controlling fault as the gas bearing boundary doesn't glide,which ensures the safety of reconstructing H gas reservoir into gas storage.Third,due to the high-speed injection and production of H gas storage,the geostress field becomes more uneven,which has a potential negative impact on the integrity of the injection and production wells of the gas storage.Fourth,during the long-term high-speed injection and production operation of H gas reservoir,the cap rock does not undergo shear and tensile failure,but the numerical simulation of geomechanics shows that the long-term high-speed injection and production of the gas storage results in the relative sliding deformation(maximum about 5 cm)on both sides of H fault in the south of the reservoir,so the sealing capacity of H fault is a weak point impacting the integrity of the gas storage.Fifth,it is recommended to deploy monitoring wells at the upper block of H fault in the south of the gas storage to strengthen the injection and production dynamic monitoring.In conclusion,this study performs a qualitative and quantitative evaluation on the trap dynamic sealing capacity of gas storages rebuilt from gas reservoirs under the action of alternating stress,and it plays an important guiding role in ensuring the long-term injection and production safety of H gas storage.展开更多
Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sands...Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sandstone,Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation,pore structure measurement and diffusion properties determination.Results indicate that with denser structures,lower porosities,much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks;the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds.To further estimate the CBM escape through caprocks,a one-dimensional CBM diffusion model is derived.Modeling calculation result demonstrates that under the same thickness,the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds,and nearly 17 times higher than sandstone,which indicates that the coal seam below caprocks like clayrock,redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone.Such conclusion is verified by the case study from III3 District,Xutuan Colliery,where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone,siltstone and sandstone.展开更多
Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consid...Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consider changes in temperature and pressure conditions,which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling.Triaxial stress-strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperaturepressure action and isothermal-variable pressure action on the basis of sample feasibility analysis.According to research,the gypsum rock's peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions,and it becomes more ductile.This reduces the amount of time it takes for the rock to transition from brittle to plastic.When temperature is taken into account,both the brittle–plastic transformation's depth limit and the lithological transformation of gypsum rocks become shallower,and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization.The sealing ability under the temperature-pressure coupling is more in line with the actual geological context when the application results of the Well#ZS5 are compared.This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved.展开更多
Underground gas storages(UGSs)rebuilt from gas reservoirs is the most popular UGS type in the world.It accounts for 75%of the total active gas of all gas storages.In order to design more scientific and reliable geolog...Underground gas storages(UGSs)rebuilt from gas reservoirs is the most popular UGS type in the world.It accounts for 75%of the total active gas of all gas storages.In order to design more scientific and reliable geological schemes for constructing the underground gas storages rebuilt from gas reservoirs and optimize the UGS operation parameters,we analyzed the UGS basic characteristics of multi-cycle high-rate injection and production.Then,the dynamic sealing capacity of traps and the wateregas high-speed interactive flow mechanism of UGSs rebuilt from gas reservoirs with complex geological conditions were investigated by both physical simulation and numerical simulation.Finally,the key technologies for evaluating the dynamic sealing capacity of caprocks and faults and the storage capacity parameters were developed.Some results were obtained.First,the alternating stress in the process of UGS injection and production weakens the original static capillary sealing capacity and mechanical integrity of caprocks to different extents,and the trap sealing capacity can be quantified and evaluated comprehensively by using dynamic breakthrough pressures,shear safety indexes and other indicators.Second,a UGS capacity design method based on effective gas-bearing pores was developed according to the local pore-based recovery mechanism revealed in the high-speed gasewater mutual flooding test.Field application in the multi-layer UGS of H shows that these technologies provide an effective guidance for the design of geologic schemes.After five cycles of injection and production,its ramp-up ratio reached 91.8%and the peak shaving capacity increased quickly to 36.3×10^(8)m^(3)from 2.7×10^(8)m^(3)in the early stage of production.Moreover,the operation indicators matched well with the design.展开更多
To optimize the magnetic fluid seal design,the single-factor method is usually used to study the e ect of the rectangular pole teeth structure parameters on the sealing capacity of the magnetic fluid seal by current r...To optimize the magnetic fluid seal design,the single-factor method is usually used to study the e ect of the rectangular pole teeth structure parameters on the sealing capacity of the magnetic fluid seal by current research,and the design formula is obtained.However,the supporting data is too few to make the results universalizable.In this paper,to obtain a wider range of applicable design formulas,a large number of modeling and simulation experiments are conducted using the co-simulation analysis experimental method of MATLAB and COMSOL.The influence of structure parameters of rectangular pole teeth and the coupling e ects of the structure parameters on the sealing capacity of sealing devices has been studied under di erent lengths of pole piece(L_(p))and seal gap(L_(g)).The results explain the influences of tooth height(L_(h)),tooth width(L_(t)),groove width(Ls),and their coupling e ects on the theoretical sealing capacity of magnetic fluid seals,and more widely applicable design formulas for pole teeth structure parameters are given.The design formulas can help to obtain good design parameters directly or reduce the optimization range when the magnetic fluid seals need to be optimized to meet the miniaturization and lightweightrequirements of magnetic fluid sealing devices or improve the sealing capacity under the same seal size.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42072166)Natural Science Foundation of Heilongjiang Province of China(Grant No.LH2020D004)Key R&D Program of Heilongjiang Province of China(Grant No.JD2023SJ26)。
文摘The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.The dynamic sealing capacity of a caprock-fault system is a critical constraint for safe operation,and is a key factor in determining the maximum operating pressure(MOP).This study proposed an efficient semi-analytical method for calculating changes in the in situ stress within the caprock.Next,the parameters of dynamic pore pressure,in situ stresses,and deformations obtained from reservoir simulations and geomechanical modeling were used for inputs for the analytical solution.Based on the calculated results,an experimental scheme for the coupled cyclic stress-permeability testing of caprock was designed.The stability analysis indicated that the caprock was not prone to fatigue shear failure under the current injection and production strategy,supported by the experimental results.The experimental results further reveal that the sealing capacity of caprock plugs may remain stable.This phenomenon is attributed to cyclic stress causing pore connectivity and microcrack initiation in certain plugs,while leading to pore compaction in others.A comparison between the dynamic pore pressure and the minimum principal stress suggests that the risk of tensile failure is extremely low.Furthermore,although the faults remain stable under the current injection and production strategies,the continuous increase in injection pressure may lead to an increased tendency for fault slip and dilation,which can cause fault slip ultimately.The MOPs corresponding to each failure mode were calculated.The minimum value of approximately 36.5 MPa at capillary sealing failure indicated that the gas breakthrough in the caprock occurred earlier than rock failure.Therefore,this minimumvalue can be used as the MOP for the target UGS.
文摘Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal,and alternating loads.This study detailed the methodology developed by Sinopec.The approach merges disciplines like geology,geomechanics,and hydrodynamics,employing both dynamic-static and qualitative-quantitative analyses.Sinopec's evaluation methods,grounded in the in situ stress analysis,include mechanistic studies,laboratory tests,geological surveys,stress analysis,and fluid-solid interactions.Through tests on the static and dynamic sealing capacity of UGS,alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults,A geomechanics-rock damage-seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity,thereby setting the maximum operational pressures.Utilizing this evaluation technique,Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs,enabling preliminary sealing capacity evaluations at UGS sites.These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.
基金Project supported by PetroChina’s Major Science and Technology Project“Study and Application of the Key Technologies of UGS Geology and Reservoir Engineering”(No.2015E-4002).
文摘In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the operation safety of gas storages,this paper takes Xinjiang H gas storage whose storage capacity and peak shaving capacity are the highest in China as the research object to establish a 3D fine geological model and a 3D dynamic geomechanical model in the regional scale of H gas storage based on the alternating change characteristics of geostress field during the high-speed cyclic injection and production of gas storage,combined with the geological,seismic,logging and various laboratory core experiment results.Then,the trap dynamic sealing capacity of H gas storage under the action of alternating stress after 14 years of depletion development of its original gas reservoir and long-term high-speed injection and production after its reconstruction from the gas reservoir was evaluated comprehensively.And the following research results were obtained.First,the change of the formation pressure in H gas storage has a significant effect on the regional geostress field.Second,after the development of the original H gas reservoir,the geostress on the two sides of the fault are greatly different,but the cap rock is not deformed and failed and the reservoir controlling fault as the gas bearing boundary doesn't glide,which ensures the safety of reconstructing H gas reservoir into gas storage.Third,due to the high-speed injection and production of H gas storage,the geostress field becomes more uneven,which has a potential negative impact on the integrity of the injection and production wells of the gas storage.Fourth,during the long-term high-speed injection and production operation of H gas reservoir,the cap rock does not undergo shear and tensile failure,but the numerical simulation of geomechanics shows that the long-term high-speed injection and production of the gas storage results in the relative sliding deformation(maximum about 5 cm)on both sides of H fault in the south of the reservoir,so the sealing capacity of H fault is a weak point impacting the integrity of the gas storage.Fifth,it is recommended to deploy monitoring wells at the upper block of H fault in the south of the gas storage to strengthen the injection and production dynamic monitoring.In conclusion,this study performs a qualitative and quantitative evaluation on the trap dynamic sealing capacity of gas storages rebuilt from gas reservoirs under the action of alternating stress,and it plays an important guiding role in ensuring the long-term injection and production safety of H gas storage.
基金Project(2016YFC0801608) supported by the National Key Research and Development Plan,ChinaProject(51574148) supported by the National Natural Science Foundation of China
文摘Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sandstone,Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation,pore structure measurement and diffusion properties determination.Results indicate that with denser structures,lower porosities,much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks;the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds.To further estimate the CBM escape through caprocks,a one-dimensional CBM diffusion model is derived.Modeling calculation result demonstrates that under the same thickness,the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds,and nearly 17 times higher than sandstone,which indicates that the coal seam below caprocks like clayrock,redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone.Such conclusion is verified by the case study from III3 District,Xutuan Colliery,where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone,siltstone and sandstone.
基金funded by the National Natural Science Foundation of China(Grant No.42172147)PetroChina Major Science and Technology Project(Grant No.ZD2019-183-002).
文摘Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consider changes in temperature and pressure conditions,which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling.Triaxial stress-strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperaturepressure action and isothermal-variable pressure action on the basis of sample feasibility analysis.According to research,the gypsum rock's peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions,and it becomes more ductile.This reduces the amount of time it takes for the rock to transition from brittle to plastic.When temperature is taken into account,both the brittle–plastic transformation's depth limit and the lithological transformation of gypsum rocks become shallower,and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization.The sealing ability under the temperature-pressure coupling is more in line with the actual geological context when the application results of the Well#ZS5 are compared.This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved.
基金supported by PetroChina Major Science and Technology Project“Study and application of geological and gas reservoir engineering technologies for underground gas storages”(No.:2015E-4002).
文摘Underground gas storages(UGSs)rebuilt from gas reservoirs is the most popular UGS type in the world.It accounts for 75%of the total active gas of all gas storages.In order to design more scientific and reliable geological schemes for constructing the underground gas storages rebuilt from gas reservoirs and optimize the UGS operation parameters,we analyzed the UGS basic characteristics of multi-cycle high-rate injection and production.Then,the dynamic sealing capacity of traps and the wateregas high-speed interactive flow mechanism of UGSs rebuilt from gas reservoirs with complex geological conditions were investigated by both physical simulation and numerical simulation.Finally,the key technologies for evaluating the dynamic sealing capacity of caprocks and faults and the storage capacity parameters were developed.Some results were obtained.First,the alternating stress in the process of UGS injection and production weakens the original static capillary sealing capacity and mechanical integrity of caprocks to different extents,and the trap sealing capacity can be quantified and evaluated comprehensively by using dynamic breakthrough pressures,shear safety indexes and other indicators.Second,a UGS capacity design method based on effective gas-bearing pores was developed according to the local pore-based recovery mechanism revealed in the high-speed gasewater mutual flooding test.Field application in the multi-layer UGS of H shows that these technologies provide an effective guidance for the design of geologic schemes.After five cycles of injection and production,its ramp-up ratio reached 91.8%and the peak shaving capacity increased quickly to 36.3×10^(8)m^(3)from 2.7×10^(8)m^(3)in the early stage of production.Moreover,the operation indicators matched well with the design.
基金Supported by National Natural Science Foundation of China(Grant No.51927810)。
文摘To optimize the magnetic fluid seal design,the single-factor method is usually used to study the e ect of the rectangular pole teeth structure parameters on the sealing capacity of the magnetic fluid seal by current research,and the design formula is obtained.However,the supporting data is too few to make the results universalizable.In this paper,to obtain a wider range of applicable design formulas,a large number of modeling and simulation experiments are conducted using the co-simulation analysis experimental method of MATLAB and COMSOL.The influence of structure parameters of rectangular pole teeth and the coupling e ects of the structure parameters on the sealing capacity of sealing devices has been studied under di erent lengths of pole piece(L_(p))and seal gap(L_(g)).The results explain the influences of tooth height(L_(h)),tooth width(L_(t)),groove width(Ls),and their coupling e ects on the theoretical sealing capacity of magnetic fluid seals,and more widely applicable design formulas for pole teeth structure parameters are given.The design formulas can help to obtain good design parameters directly or reduce the optimization range when the magnetic fluid seals need to be optimized to meet the miniaturization and lightweightrequirements of magnetic fluid sealing devices or improve the sealing capacity under the same seal size.
