In Belgium,the Boom clay was selected as a potential host formation for the disposal of high-level radioactive waste（HLW）.To demonstrate the suitability of Boom clay for bearing thermal load induced by the HLW,a lar...In Belgium,the Boom clay was selected as a potential host formation for the disposal of high-level radioactive waste（HLW）.To demonstrate the suitability of Boom clay for bearing thermal load induced by the HLW,a large-scale in-situ heater test,called PRACLAY heater test,will be conducted in the underground research laboratory（URL） in Mol.Owing to the limitations of the test（a short period of time compared with that considered in a real repository,different boundary conditions,etc.）,the test is designed to simulate,in a conservative way,the most critical state and phenomena that could occur in the host rock.The PRACLAY gallery was excavated at the end of 2007;the heating phase will begin in 2010 and will last for at least 10 years.The PRACLAY gallery itself leaves an opportunity to study the possibilities of sealing a disposal drift in Boom clay and testing the feasibility of hydraulic cut-off of any preferential pathway to the main access gallery through the excavation damage zone（EDZ） and the lining with a seal in a horizontal drift（horizontal seal）.Indeed,this is a generic problem for all deep geological disposal facilities for HLW.An annular seal made of compacted swelling bentonite will be installed in the front of the heated part of the PRACLAY gallery for these purposes.This paper provides detailed considerations on the thermo-hydro-mechanical（THM） boundary conditions for the design of the PRACLAY heater test and the seal test with the support of numerical calculations.It is believed that these important items considered in the PRACLAY heater test design also constitute key issues for the repository design.The outcome of the PRACLAY heater test will be an important milestone for the Belgian repository design.展开更多
In the context of radioactive waste disposal,an underground research laboratory(URL)is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste dis...In the context of radioactive waste disposal,an underground research laboratory(URL)is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility within a geological formation.The Meuse/Haute-Marne URL is a sitespecific facility planned to study the feasibility of a radioactive waste disposal in the Callovo-Oxfordian(COx)claystone.The thermo-hydro-mechanical(THM)behaviour of the host rock is significant for the design of the underground nuclear waste disposal facility and for its long-term safety.The French National Radioactive Waste Management Agency(Andra)has begun a research programme aiming to demonstrate the relevancy of the French high-level waste(HLW)concept.This paper presents the programme implemented from small-scale(small diameter)boreholes to full-scale demonstration experiments to study the THM effects of the thermal transient on the COx claystone and the strategy implemented in this new programme to demonstrate and optimise current disposal facility components for HLW.It shows that the French high-level waste concept is feasible and working in the COx claystone.It also exhibits that,as for other plastic clay or claystone,heating-induced pore pressure increases and that the THM behaviour is anisotropic.展开更多
Repositories for deep geological disposal of radioactive waste rely on multi-barrier systems to isolate waste from the biosphere.A multi-barrier system typically comprises the natural geological barrier provided by th...Repositories for deep geological disposal of radioactive waste rely on multi-barrier systems to isolate waste from the biosphere.A multi-barrier system typically comprises the natural geological barrier provided by the repository host rock e in our case the Opalinus Clay e and an engineered barrier system(EBS).The Swiss repository concept for spent fuel and vitrified high-level waste(HLW)consists of waste canisters,which are emplaced horizontally in the middle of an emplacement gallery and are separated from the gallery wall by granular backfill material(GBM).We describe here a selection of five in-situ experiments where characteristic hydro-mechanical(HM)and thermo-hydro-mechanical(THM)processes have been observed.The first example is a coupled HM and mine-by test where the evolution of the excavation damaged zone(EDZ)was monitored around a gallery in the Opalinus Clay(ED-B experiment).Measurements of pore-water pressures and convergences due to stress redistribution during excavation highlighted the HM behaviour.The same measurements were subsequently carried out in a heater test(HE-D)where we were able to characterise the Opalinus Clay in terms of its THM behaviour.These yielded detailed data to better understand the THM behaviours of the granular backfill and the natural host rock.For a presentation of the Swiss concept for HLW storage,we designed three demonstration experiments that were subsequently implemented in the Mont Terri rock laboratory:(1)the engineered barrier(EB)experiment,(2)the in-situ heater test on key-THM processes and parameters(HE-E)experiment,and(3)the full-scale emplacement(FE)experiment.The first demonstration experiment has been dismantled,but the last two ones are on-going.展开更多
The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical（THM） coupling phenomena and their influences on the repository safety.In this paper,the high-level waste（HLW） disposal con...The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical（THM） coupling phenomena and their influences on the repository safety.In this paper,the high-level waste（HLW） disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE BRIGHT developed by the Technical University of Catalonia in Barcelona.The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments.The calculation results are presented to show the hydro-mechanical（HM） processes during the operation phase and the THM processes in the after-closure phase.According to the simulation results,the most probable critical processes for the disposal project have been represented and analyzed.The work also provides an input for additional development regarding the design,assessment and validation of the HLW disposal concept.展开更多
As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In hi...As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In highly consolidated clayey rocks, thermal effects are particularly significantbecause of their very low permeability and water-saturated state. Thermal impact on the integrity of thegeological barriers is of most importance with regard to the long-term safety of repositories. This studyfocuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using acoupled thermo-mechanical multiphase flow （TH2M） model which is implemented in the finite elementprogramme OpenGeoSys （OGS）. The material properties of the numerical model are characterised by atransversal isotropic elastic model based on Hooke＇s law, a non-isothermal multiphase flow model basedon van Genuchten function and Darcy＇s law, and a transversal isotropic heat transport model based onFourier＇s law. In the numerical approaches, special attention has been paid to the thermal expansion ofthree different phases： gas, fluid and solid, which could induce changes in pore pressure and porosity.Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in thepresent model. The model has been applied to simulate a laboratory heating experiment on claystone.The numerical model gives a satisfactory representation of the observed material behaviour in thelaboratory experiment. The comparison of the calculated results with the laboratory findings verifies thatthe simulation with the present numerical model could provide a deeper understanding of the observedeffects. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
A formulation for the coupled analysis of thermo-hydro-mechanical （THM） problems in joints is first presented. The work involves the establishment of equilibrium and mass and energy balance equations. Balance equati...A formulation for the coupled analysis of thermo-hydro-mechanical （THM） problems in joints is first presented. The work involves the establishment of equilibrium and mass and energy balance equations. Balance equations were formulated taking into account two phases： water and air. The joint element developed was implemented in a general purpose finite element computer code for THM analysis of porous media （Code_Bright）. The program was then used to study a number of cases ranging from laboratory tests to large scale in situ tests. A numerical simulation of coupled hydraulic shear tests of rough granite joints is first presented. The tests as well as the model show the coupling between permeability and the deformation of thejoints. The experimental investigation was focused on the effects of suction on the mechanical behaviour of rock joints. Laboratory tests were performed in a direct shear cell equipped with suction control. Suction was imposed using a vapour forced convection circuit connected to the cell and controlled by an air pump. Artificial joints of Lilla claystone were prepared.Joint roughness of varying intensity was created by carving the surfaces in contact in such a manner that rock ridges of different tip angles were formed. These angles ranged from 0° （smooth joint） to 45° （very rough joint profile）. The geometric profiles of the two surfaces in contact were initially positioned in a ＂matching＂ situation. Several tests were performed for different values of suctions （200, 100, and 20 MPa） and for different values of vertical stresses （30, 60, and 150 kPa）. A constitutive model including the effects of suction and joint roughness is proposed to simulate the unsaturated behaviour of rock joints. The new constitutive law was incorporated in the code and experimental results were numerically simulated.展开更多
In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numer...In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numerical simulations are performed by using a coupled THM finite element code and two different constitutive models:a visco-elastoplastic model for geological formation and a von Mises type model for steel liner.The mechanical properties and deformation behavior of corroded steel are described in a conceptual model.Finally,a disposal tunnel supported by a steel liner is studied and a series of parametric studies is defined to demonstrate the corrosion effects of steel liner on the THM response of the claystone.The comparison of different numerical calculations exhibits that the volumetric expansion related to corrosion products has an important impact on the stress and displacement fields in the claystone surrounding the disposal tunnel.However,the evolutions of temperature and liquid pressure in the claystone are essentially controlled by its THM properties and independent of the steel corrosion.展开更多
One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) coupl...One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) coupled processes associated with an HLW disposal repository. Non-linear coupled equations, which are used to describe the THM coupled process and are suited to saturated-unsaturated porous media, are presented in this paper. A numerical method to solve these equations is put forward, and a finite element code is developed. This code is suited to the plane strain or axis-symmetry problem. Then this code is used to simulate the THM coupled process in the near field of an ideal disposal repository. The temperature vs. time, hydraulic head vs. time and stress vs. time results show that, in this assumed condition, the impact of temperature is very long (over 10 000 a) and the impact of the water head is short (about 90 d). Since the stress is induced by temperature and hydraulic head in this condition, the impact time of stress is the same as that of temperature. The results show that THM coupled processes are very important in the safety analysis of an HLW deep geological disposal repository.展开更多
To investigate and analyze the thermo-hydro-mechanical(THM) coupling phenomena of a surrounding rock mass in an argillaceous formation, a nuclear waste disposal concept in drifts was represented physically in an in-si...To investigate and analyze the thermo-hydro-mechanical(THM) coupling phenomena of a surrounding rock mass in an argillaceous formation, a nuclear waste disposal concept in drifts was represented physically in an in-situ test way. A transversely isotropic model was employed to reproduce the whole test process numerically. Parameters of the rock mass were determined by laboratory and in-situ experiments. Based on the numerical simulation results and in-situ test data, the variation processes of pore water pressure, temperature and deformation of surrounding rock were analyzed. Both the measured data and numerical results reveal that the thermal perturbation is the principal driving force which leads to the variation of pore water pressure and deformations in the surrounding rock. The temperature, pore pressure and deformation of rock mass change rapidly at each initial heating stage with a constant heating power. The temperature field near the heater borehole is relatively steady in the subsequent stages of the heating phase. However, the pore pressure and deformation fields decrease gradually with temperature remaining unchanged condition. It also shows that a transversely isotropic model can reproduce the THM coupling effects generating in the near-field of a nuclear waste repository in an argillaceous formation.展开更多
Geo-energy and geo-engineering applications,such as improved oil recovery(IOR),geologic carbon storage,and enhanced geothermal systems(EGSs),involve coupled thermo-hydro-mechanical(THM)processes that result from fluid...Geo-energy and geo-engineering applications,such as improved oil recovery(IOR),geologic carbon storage,and enhanced geothermal systems(EGSs),involve coupled thermo-hydro-mechanical(THM)processes that result from fluid injection and production.In some cases,reservoirs are highly fractured and the geomechanical response is controlled by fractures.Therefore,fractures should explicitly be included into numerical models to realistically simulate the THM responses of the subsurface.In this study,we perform coupled THM numerical simulations of water injection into naturally fractured reservoirs(NFRs)using CODE_BRIGHT and TOUGH-UDEC codes.CODE_BRIGHT is a finite element method(FEM)code that performs fully coupled THM analysis in geological media and TOUGH-UDEC sequentially solves coupled THM processes by combining a finite volume method(FVM)code that solves nonisothermal multiphase flow(TOUGH2)with a distinct element method(DEM)code that solves the mechanical problem(UDEC).First,we validate the two codes against a semi-analytical solution for water injection into a single deformable fracture considering variable permeability based on the cubic law.Then,we compare simulation results of the two codes in an idealized conceptual model that includes one horizontal fracture and in a more realistic model with multiple fractures.Each code models fractures differently.UDEC calculates fracture deformation from the fracture normal and shear stiffnesses,while CODE_BRIGHT treats fractures as equivalent porous media and uses the equivalent Young’s modulus and Poisson’s ratio of the fracture.Finally,we obtain comparable results of pressure,temperature,stress and displacement distributions and evolutions for the single horizontal fracture model.Despite some similarities,the two codes provide increasingly different results as model complexity increases.These differences highlight the challenging task of accurately modeling coupled THM processes in fractured media given their high nonlinearity.展开更多
In this paper,a coupled thermo-hydro-mechanical(THM)simulation in a faulted deformable porous medium is presented.This model involves solving the mass conservation,linear momentum balance,and energy balance equations ...In this paper,a coupled thermo-hydro-mechanical(THM)simulation in a faulted deformable porous medium is presented.This model involves solving the mass conservation,linear momentum balance,and energy balance equations which are derived from the Biot’s consolidation theory.Fluid pore pressure,solid displacement,and temperature are chosen as initial variables in these equations,and the finite element method in combination with the interface element is used for spatial discretization of continuous and discontinuities(fault)parts of the medium to solve the equations.The main purpose of this study is providing precise formulations,applicability,and ability of the triple-node zero-thickness interface element in THM modeling of faults.It should be noted that the system of equations is solved using a computer code written in Matlab program.In order to verify the developed method,simulations of index problems such as Mandel’s problem,and coupled modeling of a faulted porous medium and a faulted aquifer are presented.The modeling results obtained from the developed method show a very good agreement with those by other modeling methods,which indicates its accuracy.展开更多
文摘In Belgium,the Boom clay was selected as a potential host formation for the disposal of high-level radioactive waste（HLW）.To demonstrate the suitability of Boom clay for bearing thermal load induced by the HLW,a large-scale in-situ heater test,called PRACLAY heater test,will be conducted in the underground research laboratory（URL） in Mol.Owing to the limitations of the test（a short period of time compared with that considered in a real repository,different boundary conditions,etc.）,the test is designed to simulate,in a conservative way,the most critical state and phenomena that could occur in the host rock.The PRACLAY gallery was excavated at the end of 2007;the heating phase will begin in 2010 and will last for at least 10 years.The PRACLAY gallery itself leaves an opportunity to study the possibilities of sealing a disposal drift in Boom clay and testing the feasibility of hydraulic cut-off of any preferential pathway to the main access gallery through the excavation damage zone（EDZ） and the lining with a seal in a horizontal drift（horizontal seal）.Indeed,this is a generic problem for all deep geological disposal facilities for HLW.An annular seal made of compacted swelling bentonite will be installed in the front of the heated part of the PRACLAY gallery for these purposes.This paper provides detailed considerations on the thermo-hydro-mechanical（THM） boundary conditions for the design of the PRACLAY heater test and the seal test with the support of numerical calculations.It is believed that these important items considered in the PRACLAY heater test design also constitute key issues for the repository design.The outcome of the PRACLAY heater test will be an important milestone for the Belgian repository design.
文摘In the context of radioactive waste disposal,an underground research laboratory(URL)is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility within a geological formation.The Meuse/Haute-Marne URL is a sitespecific facility planned to study the feasibility of a radioactive waste disposal in the Callovo-Oxfordian(COx)claystone.The thermo-hydro-mechanical(THM)behaviour of the host rock is significant for the design of the underground nuclear waste disposal facility and for its long-term safety.The French National Radioactive Waste Management Agency(Andra)has begun a research programme aiming to demonstrate the relevancy of the French high-level waste(HLW)concept.This paper presents the programme implemented from small-scale(small diameter)boreholes to full-scale demonstration experiments to study the THM effects of the thermal transient on the COx claystone and the strategy implemented in this new programme to demonstrate and optimise current disposal facility components for HLW.It shows that the French high-level waste concept is feasible and working in the COx claystone.It also exhibits that,as for other plastic clay or claystone,heating-induced pore pressure increases and that the THM behaviour is anisotropic.
文摘Repositories for deep geological disposal of radioactive waste rely on multi-barrier systems to isolate waste from the biosphere.A multi-barrier system typically comprises the natural geological barrier provided by the repository host rock e in our case the Opalinus Clay e and an engineered barrier system(EBS).The Swiss repository concept for spent fuel and vitrified high-level waste(HLW)consists of waste canisters,which are emplaced horizontally in the middle of an emplacement gallery and are separated from the gallery wall by granular backfill material(GBM).We describe here a selection of five in-situ experiments where characteristic hydro-mechanical(HM)and thermo-hydro-mechanical(THM)processes have been observed.The first example is a coupled HM and mine-by test where the evolution of the excavation damaged zone(EDZ)was monitored around a gallery in the Opalinus Clay(ED-B experiment).Measurements of pore-water pressures and convergences due to stress redistribution during excavation highlighted the HM behaviour.The same measurements were subsequently carried out in a heater test(HE-D)where we were able to characterise the Opalinus Clay in terms of its THM behaviour.These yielded detailed data to better understand the THM behaviours of the granular backfill and the natural host rock.For a presentation of the Swiss concept for HLW storage,we designed three demonstration experiments that were subsequently implemented in the Mont Terri rock laboratory:(1)the engineered barrier(EB)experiment,(2)the in-situ heater test on key-THM processes and parameters(HE-E)experiment,and(3)the full-scale emplacement(FE)experiment.The first demonstration experiment has been dismantled,but the last two ones are on-going.
基金financed and supported by the German research institute "Gesellschaft für Anlagen-und Reaktorsicherheit (GRS) mbH"
文摘The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical（THM） coupling phenomena and their influences on the repository safety.In this paper,the high-level waste（HLW） disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE BRIGHT developed by the Technical University of Catalonia in Barcelona.The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments.The calculation results are presented to show the hydro-mechanical（HM） processes during the operation phase and the THM processes in the after-closure phase.According to the simulation results,the most probable critical processes for the disposal project have been represented and analyzed.The work also provides an input for additional development regarding the design,assessment and validation of the HLW disposal concept.
基金supported by BMWi (Bundesministerium für Wirtschaft und Energie,Berlin)
文摘As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In highly consolidated clayey rocks, thermal effects are particularly significantbecause of their very low permeability and water-saturated state. Thermal impact on the integrity of thegeological barriers is of most importance with regard to the long-term safety of repositories. This studyfocuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using acoupled thermo-mechanical multiphase flow （TH2M） model which is implemented in the finite elementprogramme OpenGeoSys （OGS）. The material properties of the numerical model are characterised by atransversal isotropic elastic model based on Hooke＇s law, a non-isothermal multiphase flow model basedon van Genuchten function and Darcy＇s law, and a transversal isotropic heat transport model based onFourier＇s law. In the numerical approaches, special attention has been paid to the thermal expansion ofthree different phases： gas, fluid and solid, which could induce changes in pore pressure and porosity.Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in thepresent model. The model has been applied to simulate a laboratory heating experiment on claystone.The numerical model gives a satisfactory representation of the observed material behaviour in thelaboratory experiment. The comparison of the calculated results with the laboratory findings verifies thatthe simulation with the present numerical model could provide a deeper understanding of the observedeffects. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘A formulation for the coupled analysis of thermo-hydro-mechanical （THM） problems in joints is first presented. The work involves the establishment of equilibrium and mass and energy balance equations. Balance equations were formulated taking into account two phases： water and air. The joint element developed was implemented in a general purpose finite element computer code for THM analysis of porous media （Code_Bright）. The program was then used to study a number of cases ranging from laboratory tests to large scale in situ tests. A numerical simulation of coupled hydraulic shear tests of rough granite joints is first presented. The tests as well as the model show the coupling between permeability and the deformation of thejoints. The experimental investigation was focused on the effects of suction on the mechanical behaviour of rock joints. Laboratory tests were performed in a direct shear cell equipped with suction control. Suction was imposed using a vapour forced convection circuit connected to the cell and controlled by an air pump. Artificial joints of Lilla claystone were prepared.Joint roughness of varying intensity was created by carving the surfaces in contact in such a manner that rock ridges of different tip angles were formed. These angles ranged from 0° （smooth joint） to 45° （very rough joint profile）. The geometric profiles of the two surfaces in contact were initially positioned in a ＂matching＂ situation. Several tests were performed for different values of suctions （200, 100, and 20 MPa） and for different values of vertical stresses （30, 60, and 150 kPa）. A constitutive model including the effects of suction and joint roughness is proposed to simulate the unsaturated behaviour of rock joints. The new constitutive law was incorporated in the code and experimental results were numerically simulated.
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No. 51609081)
文摘In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numerical simulations are performed by using a coupled THM finite element code and two different constitutive models:a visco-elastoplastic model for geological formation and a von Mises type model for steel liner.The mechanical properties and deformation behavior of corroded steel are described in a conceptual model.Finally,a disposal tunnel supported by a steel liner is studied and a series of parametric studies is defined to demonstrate the corrosion effects of steel liner on the THM response of the claystone.The comparison of different numerical calculations exhibits that the volumetric expansion related to corrosion products has an important impact on the stress and displacement fields in the claystone surrounding the disposal tunnel.However,the evolutions of temperature and liquid pressure in the claystone are essentially controlled by its THM properties and independent of the steel corrosion.
文摘One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) coupled processes associated with an HLW disposal repository. Non-linear coupled equations, which are used to describe the THM coupled process and are suited to saturated-unsaturated porous media, are presented in this paper. A numerical method to solve these equations is put forward, and a finite element code is developed. This code is suited to the plane strain or axis-symmetry problem. Then this code is used to simulate the THM coupled process in the near field of an ideal disposal repository. The temperature vs. time, hydraulic head vs. time and stress vs. time results show that, in this assumed condition, the impact of temperature is very long (over 10 000 a) and the impact of the water head is short (about 90 d). Since the stress is induced by temperature and hydraulic head in this condition, the impact time of stress is the same as that of temperature. The results show that THM coupled processes are very important in the safety analysis of an HLW deep geological disposal repository.
基金Project(41272287)supported by the National Natural Science Foundation of China
文摘To investigate and analyze the thermo-hydro-mechanical(THM) coupling phenomena of a surrounding rock mass in an argillaceous formation, a nuclear waste disposal concept in drifts was represented physically in an in-situ test way. A transversely isotropic model was employed to reproduce the whole test process numerically. Parameters of the rock mass were determined by laboratory and in-situ experiments. Based on the numerical simulation results and in-situ test data, the variation processes of pore water pressure, temperature and deformation of surrounding rock were analyzed. Both the measured data and numerical results reveal that the thermal perturbation is the principal driving force which leads to the variation of pore water pressure and deformations in the surrounding rock. The temperature, pore pressure and deformation of rock mass change rapidly at each initial heating stage with a constant heating power. The temperature field near the heater borehole is relatively steady in the subsequent stages of the heating phase. However, the pore pressure and deformation fields decrease gradually with temperature remaining unchanged condition. It also shows that a transversely isotropic model can reproduce the THM coupling effects generating in the near-field of a nuclear waste repository in an argillaceous formation.
基金financial support received from the“Iran’s Ministry of Science Research and Technology”(PhD students’sabbatical grants)funding from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program through the Starting Grant GEoREST(www.georest.eu)(Grant Agreement No.801809)+1 种基金support by the Korea-EU Joint Research Program of the National Research Foundation of Korea through Grant No.NRF2015K1A3A7A03074226funded by the Korean Government’s Ministry of Science and Information and Communication Technology(ICT)in the framework of the European Union’s Horizon 2020 Research and Innovation Program(Grant No.691728)。
文摘Geo-energy and geo-engineering applications,such as improved oil recovery(IOR),geologic carbon storage,and enhanced geothermal systems(EGSs),involve coupled thermo-hydro-mechanical(THM)processes that result from fluid injection and production.In some cases,reservoirs are highly fractured and the geomechanical response is controlled by fractures.Therefore,fractures should explicitly be included into numerical models to realistically simulate the THM responses of the subsurface.In this study,we perform coupled THM numerical simulations of water injection into naturally fractured reservoirs(NFRs)using CODE_BRIGHT and TOUGH-UDEC codes.CODE_BRIGHT is a finite element method(FEM)code that performs fully coupled THM analysis in geological media and TOUGH-UDEC sequentially solves coupled THM processes by combining a finite volume method(FVM)code that solves nonisothermal multiphase flow(TOUGH2)with a distinct element method(DEM)code that solves the mechanical problem(UDEC).First,we validate the two codes against a semi-analytical solution for water injection into a single deformable fracture considering variable permeability based on the cubic law.Then,we compare simulation results of the two codes in an idealized conceptual model that includes one horizontal fracture and in a more realistic model with multiple fractures.Each code models fractures differently.UDEC calculates fracture deformation from the fracture normal and shear stiffnesses,while CODE_BRIGHT treats fractures as equivalent porous media and uses the equivalent Young’s modulus and Poisson’s ratio of the fracture.Finally,we obtain comparable results of pressure,temperature,stress and displacement distributions and evolutions for the single horizontal fracture model.Despite some similarities,the two codes provide increasingly different results as model complexity increases.These differences highlight the challenging task of accurately modeling coupled THM processes in fractured media given their high nonlinearity.
文摘In this paper,a coupled thermo-hydro-mechanical(THM)simulation in a faulted deformable porous medium is presented.This model involves solving the mass conservation,linear momentum balance,and energy balance equations which are derived from the Biot’s consolidation theory.Fluid pore pressure,solid displacement,and temperature are chosen as initial variables in these equations,and the finite element method in combination with the interface element is used for spatial discretization of continuous and discontinuities(fault)parts of the medium to solve the equations.The main purpose of this study is providing precise formulations,applicability,and ability of the triple-node zero-thickness interface element in THM modeling of faults.It should be noted that the system of equations is solved using a computer code written in Matlab program.In order to verify the developed method,simulations of index problems such as Mandel’s problem,and coupled modeling of a faulted porous medium and a faulted aquifer are presented.The modeling results obtained from the developed method show a very good agreement with those by other modeling methods,which indicates its accuracy.
