Rockburst hazard in mining industry all over the world is one of the most severe hazards. It is becoming increasingly common because of the ever-growing depths of mining operations accompanied by the increasing streng...Rockburst hazard in mining industry all over the world is one of the most severe hazards. It is becoming increasingly common because of the ever-growing depths of mining operations accompanied by the increasing strength of rocks. One of the most difficult issues is to predict this hazard before the mining operations, whether geophysical investigations have been conducted or not. Polish experience in this field shows that in such cases an effective solution can be the geomechanical method. Therefore, extensive studies on rockburst hazard should focus on three main aspects:(1) rock mass and rock(and coal)predisposition to rockburst–laboratory tests and empirical analyses based on lithology,(2) identification of the potential places with stress and elastic energy concentration in the rock mass within the area planned for exploitation, and(3) the assessment of the impact of mining tremors on the surface. This preliminary geomechanical analysis assesses the propensity of the rock mass to dynamic breakage and provides quantitatively the level of rockburst hazard. The paper presents Polish experience in rockburst hazard assessment with the use of geomechanical method, as well as some solutions and examples of such analyses.展开更多
In open-pit mines,pit slope as one of the important parameters affects the mine economy and total minable reserve,and it is also affected by different uncertainties which arising from many sources.One of the most crit...In open-pit mines,pit slope as one of the important parameters affects the mine economy and total minable reserve,and it is also affected by different uncertainties which arising from many sources.One of the most critical sources of uncertainty effects on the pit slope design is rock mass geomechanical properties.By comparing the probability of failure resulted from deterministic procedure and probabilistic one,this paper investigated the effects of aforesaid uncertainties on open-pit slope stability in metal mines.In this way,to reduce the effect of variance,it implemented Latin Hypercube Sampling(LHS)technique.Furthermore,a hypothesis test was exerted to compare the effects on two cases in Middle East.Subsequently,the investigation approved high influence of geomechanical uncertainties on overall pit steepness and stability in both iron and copper mines,though on the first case the effects were just over.展开更多
It is shown that modern achievements in the field of experimental and theoretical researches and developments of innovative measuring systems for monitoring of non-linear dynamic and kinematic characteristics allow to...It is shown that modern achievements in the field of experimental and theoretical researches and developments of innovative measuring systems for monitoring of non-linear dynamic and kinematic characteristics allow to formulate basics of new academic discipline,designated as“geomechanical thermodynamics”.The following circumstances can be considered as the most important prerequisites for development of this new discipline.(1)Practical completeness of the classical thermodynamics,based on kinetic gas theory and molecular movements in solid bodies;(2)Creation of“formular construction tool”for the description of dynamic and kinematic characteristics of pendulum waves and energy conditions of their occurrence and propagation from dynamic sources,located in multi-phased stressed rock mass and geomaterials with block-hierarchical structure;(3)Principal opportunity to establish formal relations between substantial energy carriers of“packages”of nonlinear pendulum waves(geoblocks of certain hierarchical levels according to their diameters)and“molecules”:their movement,velocity and acceleration of the“molecules”↔“geoblock”;“force interactions between molecules”↔“non-linear elastic interaction between geoblocks”,etc.The term of“geomechanical temperature”is introduced and its analytical expression,which is proportional to kinetic energy of movement of geoblocks with defined volume for their hierarchical subsequence at“confined”conditions of the stressed rock mass,is shown.The similar aspects are discussed,when emission acousticelectromagnetic fields are fixed using corresponding coefficients of mechanical-electrical and mechanicalacoustic transformations.In order to quantitively describe the evolution of energy state of local zones of stressstrain concentration and surroundings of their non-linear influence from catastrophic events at the natural and mine-engineering systems(earthquakes,rock bursts,etc.),the terms of their geomechanical and thermodynamic stages are introduced and展开更多
Static Poisson’s ratio(vs)is crucial for determining geomechanical properties in petroleum applications,namely sand production.Some models have been used to predict vs;however,the published models were limited to spe...Static Poisson’s ratio(vs)is crucial for determining geomechanical properties in petroleum applications,namely sand production.Some models have been used to predict vs;however,the published models were limited to specific data ranges with an average absolute percentage relative error(AAPRE)of more than 10%.The published gated recurrent unit(GRU)models do not consider trend analysis to show physical behaviors.In this study,we aim to develop a GRU model using trend analysis and three inputs for predicting n s based on a broad range of data,n s(value of 0.1627-0.4492),bulk formation density(RHOB)(0.315-2.994 g/mL),compressional time(DTc)(44.43-186.9 μs/ft),and shear time(DTs)(72.9-341.2μ s/ft).The GRU model was evaluated using different approaches,including statistical error an-alyses.The GRU model showed the proper trends,and the model data ranges were wider than previous ones.The GRU model has the largest correlation coefficient(R)of 0.967 and the lowest AAPRE,average percent relative error(APRE),root mean square error(RMSE),and standard deviation(SD)of 3.228%,1.054%,4.389,and 0.013,respectively,compared to other models.The GRU model has a high accuracy for the different datasets:training,validation,testing,and the whole datasets with R and AAPRE values were 0.981 and 2.601%,0.966 and 3.274%,0.967 and 3.228%,and 0.977 and 2.861%,respectively.The group error analyses of all inputs show that the GRU model has less than 5% AAPRE for all input ranges,which is superior to other models that have different AAPRE values of more than 10% at various ranges of inputs.展开更多
Slope failure triggered by heavy rainfall is very common in tropical and subtropical regions and a cause of major social and economic damage.Landslide susceptibility maps can be generated using geographical informatio...Slope failure triggered by heavy rainfall is very common in tropical and subtropical regions and a cause of major social and economic damage.Landslide susceptibility maps can be generated using geographical information systems(GIS)and limit equilibrium slope stability models coupled or not to hydrological equations.This study investigated the efficacy of four models used for slope stability analysis in predicting landslide-susceptible areas in a GIS environment.The selected models are the infinite slope,the shallow slope stability model(SHALSTAB),the stability index mapping(SINMAP),and the transient rainfall infiltration and grid-based regional slope-stability(TRIGRS).For comparisons,the authors(a)included the infinite slope equation in all models,(b)clearly defined input parameters and failure triggering mechanisms for each simulation(soil depth,water table height,rainfall intensity),(c)determined appropriate values for each model to obtain stability levels that represented similar hydrogeotechnical conditions,and(d)considered upper-third areas of landslide scars to estimate the reliability of susceptibility maps using validation indices.An intense rainfall event occurred in Serra do Mar,Brazil in January 2014 triggered hundreds of landslides and was used for back analysis and evaluation of the slope stability analysis models.When rainfall intensity is not considered,the four models produced very similar results.The most reliable landslide susceptibility map was generated using TRIGRS and considering the granite residual granite soils geological-geotechnical unit,subjected to a rainfall intensity of 210 mm for 2 h under unsaturated conditions.展开更多
Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.U...Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.Using this knowledge the JTech bolt was developed and subjected to a thorough program to test,gather data and validate the bolt performance in varying domains.By conducting FE(finite element)modeling,the simulation reviews the JTech bolt design evaluating the effects of threadbar geometric variation,threadbar and nut engagement results under high stress,coating friction response and effects of thread tolerance extremes on the failure mode.These results determine safety factors,tolerances and quality management criteria.Once manufactured,in-situ system testing,laboratory and underground short encapsulation testing,resin mixing testing,double shear testing and dynamic testing at varying velocity and mass,determine the system’s capacity and effectiveness in static,quasi-static and dynamic mining environments.In this paper,the process and results are described.展开更多
A simplified geomechanical model was proposed by considering three typical neckingtype slopes;this model lays a foundation for the further investigation of the deformation behaviors of such slopes.Three physical model...A simplified geomechanical model was proposed by considering three typical neckingtype slopes;this model lays a foundation for the further investigation of the deformation behaviors of such slopes.Three physical models of necking-type slopes were built according to the geomechanical model with slope evolution stages.Finally,preliminary calculations related to the arching effect in the physical model were conducted.Three evolution stages of necking-type slopes,namely,the initial stage,compression stage,and failure stage,were presented based on the formation and disappearance of the arching effect within the slope.The specific parameters of the geomechanical model were given.In the setup of the tilting test,the failure angle of the necking-type slope model was calculated to be approximately 50°with a large lateral resistance coefficient.The proposed geomechanical model and physical models of necking-type slopes provide guidance for the establishment of geomechanical and physical models of landslides at specific sites.展开更多
Hydropower projects are rapidly developing in China at present, and a number of high daras and large reservoirs are currently under construction or will soon be built. These large projects are mainly located on the gr...Hydropower projects are rapidly developing in China at present, and a number of high daras and large reservoirs are currently under construction or will soon be built. These large projects are mainly located on the great rivers in West China with complicated topographical and geological conditions. Evaluation of stability and safety of these high dam projects is an important topic. Geomechanical model test is one of the main methods to study the global stability of high dam and foundation. In this paper, a comprehensive testing method that combines overloading and strength reduction in a model is proposed. In this method, both the influence of excessive flooding and the effects of strength reduction of rock masses and weak structural planes on dam stability are considered. Thus, the comprehensive testing method can accurately incorporate multiple factors that affect the global stability of high dam and its foundation. Based on the failure testing principle and model similarity theory, a similarity relation formula for safety evaluation through comprehensive test is established. A new model material, temperature-dependent analogous material, is also developed. By rising the temperature and reducing the strength of the mod,~l material, the mechanical behaviors resulting from gradual strength reduction can be simulated. Thus, the comprehensive testing method is realized in a single model. For case studies, the comprehensive geomechanical model test is conducted for Jinpinlg I and Xiaowan high arch dam projects.展开更多
This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on...This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on the geological data in Horn River Basin,Northeast British Columbia,Canada.The modeling results indicate that the maximum magnitude of seismic events appears at the fracturing stage.The increment of fluid volume in the fault determines the cumulative moment and maximum fault slippage,both of which are essentially proportional to the fluid volume.After backflow starts,the fluid near the joint intersection keeps flowing into the critically stressed fault,rather than backflows to the wellbore.Although fault slippage is affected by the changes of both pore pressure and ambient rock stress,their contributions are different at fracturing and backflow stages.At fracturing stage,pore pressure change shows a dominant effect on induced fault slippage.While at backflow stage,because the fault plane is under a critical stress state,any minor disturbance would trigger a fault slippage.The energy analysis indicates that aseismic deformation takes up a majority of the total deformation energy during hydraulic fracturing.A common regularity is found in both fracturing-and backflow-induced seismicity that the cumulative moment and maximum fault slippage are nearly proportional to the injected fluid volume.This study shows some novel insights into interpreting fracturing-and backflowinduced seismicity,and provides useful information for controlling and mitigating seismic hazards due to hydraulic fracturing.展开更多
In order to investigate the influence of face instability for tunnels with different burial depths in sandy cobble strata on earth pressure and the instability region,geomechanical model tests and numerical simulation...In order to investigate the influence of face instability for tunnels with different burial depths in sandy cobble strata on earth pressure and the instability region,geomechanical model tests and numerical simulations were performed.The continuous excavation method was adopted to reduce the pressure of the soil bin and restore the real engineering situation.Earth pressure in three directions of the obser-vation section in front of the tunnel face was monitored during the tunneling of the shield.Evolutions of the lateral stress ratios at dif-ferent stages were also investigated.The instability area of the shield tunnel face in sandy cobble strata with different burial depth ratios during the instability stage was obtained based on the change ratio of earth pressure and compared with existing researches.The earth pressure began to change when the excavation was one shield diameter away from the observation section,and when the excavation reached the observation section,the earth pressure decreased significantly.The burial depth of shield tunnel in the sandy cobble strata has a significant impact on the evolution of soil arch and the size of the failure area.The numerical simulation of the continuum medium cannot reflect the stress redistribution characteristics of the granular body like sandy cobble strata,and the failure area or stress distur-bance area obtained by the model test is larger than the numerical simulation result.Existing methods have deviations in analyzing the failure area of shield tunnel face in sandy cobble strata.It provides not only guidance for shield tunnel excavation engineering in sandy cobble strata,but also a reference for the theoretical research on failure areas.展开更多
The wellbore stability of a vertical well through the sandstone reservoir layers of the Asmari oil-bearing formation in south-west Iran is investigated.The safe drilling-fluid density range for maintaining wellbore st...The wellbore stability of a vertical well through the sandstone reservoir layers of the Asmari oil-bearing formation in south-west Iran is investigated.The safe drilling-fluid density range for maintaining wellbore stability is determined and simulated using FLAC3 D software and a finite volume model established with drilled strata geomechanical features.The initiation of plastic condition is used to determine the safe mud weight window(SMWW)in specific sandstone layers.The effects of rock strength parameters,major stresses around the wellbore and pore pressure on the SMWW are investigated for this wellbore.Sensitivity analysis reveals that a reduction in cohesion and internal friction angle values leads to a significant narrowing of the SMWW.On the other hand,the reduction of pore pressure and the ratio between maximum and minimum horizontal stresses causes the SMWW to widen significantly.The ability to readily quantify changes in SMWW indicates that the developed model is suitable as a well planning and monitoring tool.展开更多
This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground d...This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground deformation,fault reactivation,induced seismicity and crack propagation,is presented.It is indicated that although all the processes involved are not fully understood,integration of all available data,such as ground survey,geological conditions,microseismicity and ground level deformation,has led to many new insights into the rock mechanical response to CO2injection.The review also shows that in geomechanical modeling,continuum modeling methods are predominant compared with discontinuum methods.It is recommended to develop continuum-discontinuum numerical methods since they are more convenient for geomechanical modeling of CO2geological storage,especially for fracture propagation simulation.The Mohr-Coulomb criterion is widely used in prediction of rock mass mechanical behavior.It would be better to use a criterion considering the effect of the intermediate principal stress on rock mechanical behavior,especially for the stability analysis of deeply seated rock engineering.Some challenges related to geomechanical modeling of CO2geological storage are also discussed.展开更多
Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, ea...Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(Vp) and S-wave(Vs) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in Vpand Vsare estimated to be <1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson’s ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.展开更多
The landslide hazards occurring in the complex geological genesis accumulation body are usually controlled by the coupling action of many internal and external factors.Therefore,this paper takes the dam-front Danbo ac...The landslide hazards occurring in the complex geological genesis accumulation body are usually controlled by the coupling action of many internal and external factors.Therefore,this paper takes the dam-front Danbo accumulation body landslide of Yangfanggou hydropower station on the Yalong River as the geological prototype,and discusses the process and mechanism of slope stability degradation under the combined action of rainfall and slope construction.Based on the detailed understanding of the basic characteristics of the accumulation body,the development characteristics of the landslide and the construction situation of the slope engineering,the study conducted correlation analysis between rainfall and landslide displacement,the physical and mechanical tests of all types of rocksoil masses,and the numerical simulation testing of seepage field variation of the landslide section.It is found that the special slope structure and material composition of the old landslide accumulation layer on the upper part of the Danbo accumulation body are the internal factors for the occurrence of thrust loadinduced landslide,and the construction of the slope engineering not only creates free space conditions for sliding,but also provides channels for the infiltration of rainfall into the slope after confluence,which is an external factor that caused the mechanical properties of the sliding zone soil to gradually weaken from the trailing edge to the leading edge.The geomechanical model of such landslide is that the active section of the trailing edge produces the"source of force",the transition section of the middle section affects the occurrence of sliding,and the anti-sliding section of the leading edge controls the occurrence of landslide hazards.The results of this research provide not only a useful supplement to the theory of landslide formation mechanisms but also a scientific basis for guiding the prevention and control of similar hazards.展开更多
The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining un...The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.展开更多
Displacement-monitoring-based back analysis is a popular method for geomechanical parameter estimation.However,due to the delayed installation of multi-point extensometers,the monitoring curve is only a part of the ov...Displacement-monitoring-based back analysis is a popular method for geomechanical parameter estimation.However,due to the delayed installation of multi-point extensometers,the monitoring curve is only a part of the overall one,leading to displacement loss.Besides,the monitoring and construction time on the monitoring curve is difficult to determine.In the literature,the final displacement was selected for the back analysis,which could induce unreliable results.In this paper,a displacement-based back analysis method to mitigate the influence of displacement loss is developed.A robust hybrid optimization algorithm is proposed as a substitute for time-consuming numerical simulation.It integrates the strengths of the nonlinear mapping and prediction capability of the support vector machine(SVM)algorithm,the global searching and optimization characteristics of the optimized particle swarm optimization(OPSO)algorithm,and the nonlinear numerical simulation capability of ABAQUS.To avoid being trapped in the local optimum and to improve the efficiency of optimization,the standard PSO algorithm is improved and is compared with other three algorithms(genetic algorithm(GA),simulated annealing(SA),and standard PSO).The results indicate the superiority of OPSO algorithm.Finally,the hybrid optimization algorithm is applied to an engineering project.The back-analyzed parameters are submitted to numerical analysis,and comparison between the calculated and monitoring displacement curve shows that this hybrid algorithm can offer a reasonable reference for geomechanical parameters estimation.展开更多
Geomechanics as the knowledge of rock deformation and stability is an indispensable part of all field development plans.Conducting geomechanical analyses leads to a safer and more efficient operation otherwise differe...Geomechanics as the knowledge of rock deformation and stability is an indispensable part of all field development plans.Conducting geomechanical analyses leads to a safer and more efficient operation otherwise different kinds of instability and distortion might occur.In this study,the geomechanical behavior of Ilam and Sarvak formations of an oil field in southwest of Iran was investigated.The research objectives can be summarized as wellbore stability evaluation and predicting the value of reservoir subsidence due to pressure drop as a result of reservoir fluid production.To fulfill these,a set of petrophysical logs run in the exploration well of this green field were collected.Next,using empirical correlations and statistical methods,required data for evaluating wellbore stability during drilling,specifying safe mud window to discover reservoir breakdown pressure,predicting the possibility of wellbore collapse in field lifetime,and assessing reservoir subsidence were determined.The results revealed that the average subsidence value as the consequence of production within 21 years is 0.275 ft Which is not significant.In terms of wellbore stability,it was concluded that all horizontal and vertical wells remain stable during this time period.Briefly to conclude,field development is not associated with alarming incidents from geomechanical aspect.展开更多
This work develops a three-dimensional(3D) multiscale model to analyze a complex carbon dioxide(CO_2) faulted reservoir that includes some key geologic features of the San Andreas and nearby faults southwest of the Ki...This work develops a three-dimensional(3D) multiscale model to analyze a complex carbon dioxide(CO_2) faulted reservoir that includes some key geologic features of the San Andreas and nearby faults southwest of the Kimberlina site.The model uses the STOMP-CO2 code for flow modeling that is coupled to the ABAQUS~ finite element package for geomechanical analysis.A 3D ABAQUS~ finite element model is developed that contains a large number of 3D solid elements with two nearly parallel faults whose damage zones and cores are discretized using the same continuum elements.Five zones with different mineral compositions are considered:shale,sandstone,fault damaged sandstone,fault damaged shale,and fault core.Rocks' elastic properties that govern their poroelastic behavior are modeled by an Eshelby-Mori-Tanaka approach(EMTA).which can account for up to 15 mineral phases.The permeability of fault damage zones affected by crack density and orientations is also predicted by an EMTA formulation.A STOMP-CO2 grid that exactly maps the ABAQUS~ finite element model is built for coupled hydromechanical analyses.Simulations of the reservoir assuming three different crack pattern situations(including crack volume fraction and orientation) for the fault damage zones are performed to predict the potential leakage of CO_2 due to cracks that enhance the permeability of the fault damage zones.The results illustrate the important effect of the crack orientation on fault permeability that can lead to substantial leakage along the fault attained by the expansion of the CO_2 plume.Potential hydraulic fracture and tendency for the faults to slip are also examined and discussed in terms of stress distributions and geomechanical properties.展开更多
In this paper,the geomechanical impact of large-scale carbon dioxide(CO) storage in depleted Dutch gas fields is compared with the impact of COstorage in saline aquifers.The geomechanical behaviour of four potential C...In this paper,the geomechanical impact of large-scale carbon dioxide(CO) storage in depleted Dutch gas fields is compared with the impact of COstorage in saline aquifers.The geomechanical behaviour of four potential COstorage sites is examined using flow and geomechanical simulations.Many gas reservoirs in the Netherlands are found in fault blocks,one to a few kilometres wide,laterally bounded by sealing faults.Aquifer depletion or re-pressurization in the lateral direction is seldom an issue because of a lack of active aquifers.Reservoir pressure changes are therefore limited to a gas-bearing fault block,while the induced stress changes affect the gas reservoir and extend 1-3 km away into the surrounding rock.Arguments in favour of COstorage in depleted gas fields are:proven seal quality,availability of field data,no record of seal integrity failure by fault reactivation from the seismically active producing Dutch gas fields,and the potential benefits of restoring the virgin formation pressure and stress state to geomechanical stability.On the other hand,COinjection in saline aquifers causes pressure build-up that exceeds the virgin hydrostatic pressure.Stress perturbations resulting from pressure build-up affect large areas,extending tens of kilometres away from the injection wells.Induced stresses in top seals are.however,small and do not exceed a few tenths of megapascal for a pressure build-up of a few megapascals in the storage formation.Geomechanical effects on top seals are weak,but could be enhanced close to the injection zone by the thermal effects of injection.Uncertainties related to characterisation of large areas affected by pressure build-up are significant,and seal quality and continuity are more difficult to be demonstrated for aquifers than for depleted gas reservoirs that have held hydrocarbons for millions of years.展开更多
文摘Rockburst hazard in mining industry all over the world is one of the most severe hazards. It is becoming increasingly common because of the ever-growing depths of mining operations accompanied by the increasing strength of rocks. One of the most difficult issues is to predict this hazard before the mining operations, whether geophysical investigations have been conducted or not. Polish experience in this field shows that in such cases an effective solution can be the geomechanical method. Therefore, extensive studies on rockburst hazard should focus on three main aspects:(1) rock mass and rock(and coal)predisposition to rockburst–laboratory tests and empirical analyses based on lithology,(2) identification of the potential places with stress and elastic energy concentration in the rock mass within the area planned for exploitation, and(3) the assessment of the impact of mining tremors on the surface. This preliminary geomechanical analysis assesses the propensity of the rock mass to dynamic breakage and provides quantitatively the level of rockburst hazard. The paper presents Polish experience in rockburst hazard assessment with the use of geomechanical method, as well as some solutions and examples of such analyses.
文摘In open-pit mines,pit slope as one of the important parameters affects the mine economy and total minable reserve,and it is also affected by different uncertainties which arising from many sources.One of the most critical sources of uncertainty effects on the pit slope design is rock mass geomechanical properties.By comparing the probability of failure resulted from deterministic procedure and probabilistic one,this paper investigated the effects of aforesaid uncertainties on open-pit slope stability in metal mines.In this way,to reduce the effect of variance,it implemented Latin Hypercube Sampling(LHS)technique.Furthermore,a hypothesis test was exerted to compare the effects on two cases in Middle East.Subsequently,the investigation approved high influence of geomechanical uncertainties on overall pit steepness and stability in both iron and copper mines,though on the first case the effects were just over.
基金support of Russian Foundation for Basic Research(project No.20-05-00051).
文摘It is shown that modern achievements in the field of experimental and theoretical researches and developments of innovative measuring systems for monitoring of non-linear dynamic and kinematic characteristics allow to formulate basics of new academic discipline,designated as“geomechanical thermodynamics”.The following circumstances can be considered as the most important prerequisites for development of this new discipline.(1)Practical completeness of the classical thermodynamics,based on kinetic gas theory and molecular movements in solid bodies;(2)Creation of“formular construction tool”for the description of dynamic and kinematic characteristics of pendulum waves and energy conditions of their occurrence and propagation from dynamic sources,located in multi-phased stressed rock mass and geomaterials with block-hierarchical structure;(3)Principal opportunity to establish formal relations between substantial energy carriers of“packages”of nonlinear pendulum waves(geoblocks of certain hierarchical levels according to their diameters)and“molecules”:their movement,velocity and acceleration of the“molecules”↔“geoblock”;“force interactions between molecules”↔“non-linear elastic interaction between geoblocks”,etc.The term of“geomechanical temperature”is introduced and its analytical expression,which is proportional to kinetic energy of movement of geoblocks with defined volume for their hierarchical subsequence at“confined”conditions of the stressed rock mass,is shown.The similar aspects are discussed,when emission acousticelectromagnetic fields are fixed using corresponding coefficients of mechanical-electrical and mechanicalacoustic transformations.In order to quantitively describe the evolution of energy state of local zones of stressstrain concentration and surroundings of their non-linear influence from catastrophic events at the natural and mine-engineering systems(earthquakes,rock bursts,etc.),the terms of their geomechanical and thermodynamic stages are introduced and
基金The authors thank the Yayasan Universiti Teknologi PETRONAS(YUTP FRG Grant No.015LC0-428)at Universiti Teknologi PETRO-NAS for supporting this study.
文摘Static Poisson’s ratio(vs)is crucial for determining geomechanical properties in petroleum applications,namely sand production.Some models have been used to predict vs;however,the published models were limited to specific data ranges with an average absolute percentage relative error(AAPRE)of more than 10%.The published gated recurrent unit(GRU)models do not consider trend analysis to show physical behaviors.In this study,we aim to develop a GRU model using trend analysis and three inputs for predicting n s based on a broad range of data,n s(value of 0.1627-0.4492),bulk formation density(RHOB)(0.315-2.994 g/mL),compressional time(DTc)(44.43-186.9 μs/ft),and shear time(DTs)(72.9-341.2μ s/ft).The GRU model was evaluated using different approaches,including statistical error an-alyses.The GRU model showed the proper trends,and the model data ranges were wider than previous ones.The GRU model has the largest correlation coefficient(R)of 0.967 and the lowest AAPRE,average percent relative error(APRE),root mean square error(RMSE),and standard deviation(SD)of 3.228%,1.054%,4.389,and 0.013,respectively,compared to other models.The GRU model has a high accuracy for the different datasets:training,validation,testing,and the whole datasets with R and AAPRE values were 0.981 and 2.601%,0.966 and 3.274%,0.967 and 3.228%,and 0.977 and 2.861%,respectively.The group error analyses of all inputs show that the GRU model has less than 5% AAPRE for all input ranges,which is superior to other models that have different AAPRE values of more than 10% at various ranges of inputs.
基金supported by grants2017/26081-8,S?o Paulo Research Foundation(FAPESP)130594/2017-2,Brazilian National Council for Scientific and Technological Development(CNPq)。
文摘Slope failure triggered by heavy rainfall is very common in tropical and subtropical regions and a cause of major social and economic damage.Landslide susceptibility maps can be generated using geographical information systems(GIS)and limit equilibrium slope stability models coupled or not to hydrological equations.This study investigated the efficacy of four models used for slope stability analysis in predicting landslide-susceptible areas in a GIS environment.The selected models are the infinite slope,the shallow slope stability model(SHALSTAB),the stability index mapping(SINMAP),and the transient rainfall infiltration and grid-based regional slope-stability(TRIGRS).For comparisons,the authors(a)included the infinite slope equation in all models,(b)clearly defined input parameters and failure triggering mechanisms for each simulation(soil depth,water table height,rainfall intensity),(c)determined appropriate values for each model to obtain stability levels that represented similar hydrogeotechnical conditions,and(d)considered upper-third areas of landslide scars to estimate the reliability of susceptibility maps using validation indices.An intense rainfall event occurred in Serra do Mar,Brazil in January 2014 triggered hundreds of landslides and was used for back analysis and evaluation of the slope stability analysis models.When rainfall intensity is not considered,the four models produced very similar results.The most reliable landslide susceptibility map was generated using TRIGRS and considering the granite residual granite soils geological-geotechnical unit,subjected to a rainfall intensity of 210 mm for 2 h under unsaturated conditions.
文摘Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.Using this knowledge the JTech bolt was developed and subjected to a thorough program to test,gather data and validate the bolt performance in varying domains.By conducting FE(finite element)modeling,the simulation reviews the JTech bolt design evaluating the effects of threadbar geometric variation,threadbar and nut engagement results under high stress,coating friction response and effects of thread tolerance extremes on the failure mode.These results determine safety factors,tolerances and quality management criteria.Once manufactured,in-situ system testing,laboratory and underground short encapsulation testing,resin mixing testing,double shear testing and dynamic testing at varying velocity and mass,determine the system’s capacity and effectiveness in static,quasi-static and dynamic mining environments.In this paper,the process and results are described.
基金funded by the National Nature Science Foundation of China(No.42207216)the National Major Scientific Instruments and Equipment Development Projects of China(No.41827808)the National Key Research and Development Program of China(No.2017YFC1501305)。
文摘A simplified geomechanical model was proposed by considering three typical neckingtype slopes;this model lays a foundation for the further investigation of the deformation behaviors of such slopes.Three physical models of necking-type slopes were built according to the geomechanical model with slope evolution stages.Finally,preliminary calculations related to the arching effect in the physical model were conducted.Three evolution stages of necking-type slopes,namely,the initial stage,compression stage,and failure stage,were presented based on the formation and disappearance of the arching effect within the slope.The specific parameters of the geomechanical model were given.In the setup of the tilting test,the failure angle of the necking-type slope model was calculated to be approximately 50°with a large lateral resistance coefficient.The proposed geomechanical model and physical models of necking-type slopes provide guidance for the establishment of geomechanical and physical models of landslides at specific sites.
基金Supported by the National Natural Science Foundation of China (51109152)the National Basic Research Program of China (973 Program) (2010CB226802)the Doctoral Programs Foundation of the Ministry of Education of China (20100181110077)
文摘Hydropower projects are rapidly developing in China at present, and a number of high daras and large reservoirs are currently under construction or will soon be built. These large projects are mainly located on the great rivers in West China with complicated topographical and geological conditions. Evaluation of stability and safety of these high dam projects is an important topic. Geomechanical model test is one of the main methods to study the global stability of high dam and foundation. In this paper, a comprehensive testing method that combines overloading and strength reduction in a model is proposed. In this method, both the influence of excessive flooding and the effects of strength reduction of rock masses and weak structural planes on dam stability are considered. Thus, the comprehensive testing method can accurately incorporate multiple factors that affect the global stability of high dam and its foundation. Based on the failure testing principle and model similarity theory, a similarity relation formula for safety evaluation through comprehensive test is established. A new model material, temperature-dependent analogous material, is also developed. By rising the temperature and reducing the strength of the mod,~l material, the mechanical behaviors resulting from gradual strength reduction can be simulated. Thus, the comprehensive testing method is realized in a single model. For case studies, the comprehensive geomechanical model test is conducted for Jinpinlg I and Xiaowan high arch dam projects.
基金supported by the Key Innovation Team Program of Innovation Talents Promotion Plan by Ministry of Science and Technology of China(Grant No.2016RA4059)National Natural Science Foundation of China(Grant Nos.41672268 and 41772286)。
文摘This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on the geological data in Horn River Basin,Northeast British Columbia,Canada.The modeling results indicate that the maximum magnitude of seismic events appears at the fracturing stage.The increment of fluid volume in the fault determines the cumulative moment and maximum fault slippage,both of which are essentially proportional to the fluid volume.After backflow starts,the fluid near the joint intersection keeps flowing into the critically stressed fault,rather than backflows to the wellbore.Although fault slippage is affected by the changes of both pore pressure and ambient rock stress,their contributions are different at fracturing and backflow stages.At fracturing stage,pore pressure change shows a dominant effect on induced fault slippage.While at backflow stage,because the fault plane is under a critical stress state,any minor disturbance would trigger a fault slippage.The energy analysis indicates that aseismic deformation takes up a majority of the total deformation energy during hydraulic fracturing.A common regularity is found in both fracturing-and backflow-induced seismicity that the cumulative moment and maximum fault slippage are nearly proportional to the injected fluid volume.This study shows some novel insights into interpreting fracturing-and backflowinduced seismicity,and provides useful information for controlling and mitigating seismic hazards due to hydraulic fracturing.
基金the financial support provided by Natural Science Foundation of China(Grant Nos.51978019,52278382)Beijing Natural Science Foundation,China(Grant No.8222004).
文摘In order to investigate the influence of face instability for tunnels with different burial depths in sandy cobble strata on earth pressure and the instability region,geomechanical model tests and numerical simulations were performed.The continuous excavation method was adopted to reduce the pressure of the soil bin and restore the real engineering situation.Earth pressure in three directions of the obser-vation section in front of the tunnel face was monitored during the tunneling of the shield.Evolutions of the lateral stress ratios at dif-ferent stages were also investigated.The instability area of the shield tunnel face in sandy cobble strata with different burial depth ratios during the instability stage was obtained based on the change ratio of earth pressure and compared with existing researches.The earth pressure began to change when the excavation was one shield diameter away from the observation section,and when the excavation reached the observation section,the earth pressure decreased significantly.The burial depth of shield tunnel in the sandy cobble strata has a significant impact on the evolution of soil arch and the size of the failure area.The numerical simulation of the continuum medium cannot reflect the stress redistribution characteristics of the granular body like sandy cobble strata,and the failure area or stress distur-bance area obtained by the model test is larger than the numerical simulation result.Existing methods have deviations in analyzing the failure area of shield tunnel face in sandy cobble strata.It provides not only guidance for shield tunnel excavation engineering in sandy cobble strata,but also a reference for the theoretical research on failure areas.
文摘The wellbore stability of a vertical well through the sandstone reservoir layers of the Asmari oil-bearing formation in south-west Iran is investigated.The safe drilling-fluid density range for maintaining wellbore stability is determined and simulated using FLAC3 D software and a finite volume model established with drilled strata geomechanical features.The initiation of plastic condition is used to determine the safe mud weight window(SMWW)in specific sandstone layers.The effects of rock strength parameters,major stresses around the wellbore and pore pressure on the SMWW are investigated for this wellbore.Sensitivity analysis reveals that a reduction in cohesion and internal friction angle values leads to a significant narrowing of the SMWW.On the other hand,the reduction of pore pressure and the ratio between maximum and minimum horizontal stresses causes the SMWW to widen significantly.The ability to readily quantify changes in SMWW indicates that the developed model is suitable as a well planning and monitoring tool.
基金finically supported by the National Natural Science Foundation of China(Grant Nos.41272349 and 51322906)Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDB-SSW-DQC029)
文摘This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground deformation,fault reactivation,induced seismicity and crack propagation,is presented.It is indicated that although all the processes involved are not fully understood,integration of all available data,such as ground survey,geological conditions,microseismicity and ground level deformation,has led to many new insights into the rock mechanical response to CO2injection.The review also shows that in geomechanical modeling,continuum modeling methods are predominant compared with discontinuum methods.It is recommended to develop continuum-discontinuum numerical methods since they are more convenient for geomechanical modeling of CO2geological storage,especially for fracture propagation simulation.The Mohr-Coulomb criterion is widely used in prediction of rock mass mechanical behavior.It would be better to use a criterion considering the effect of the intermediate principal stress on rock mechanical behavior,especially for the stability analysis of deeply seated rock engineering.Some challenges related to geomechanical modeling of CO2geological storage are also discussed.
文摘Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(Vp) and S-wave(Vs) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in Vpand Vsare estimated to be <1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson’s ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.
基金funded by the National Natural Science Foundation of China(Grant Nos.41572308 and 41977226)Power China Huadong Engineering Corporation Limited。
文摘The landslide hazards occurring in the complex geological genesis accumulation body are usually controlled by the coupling action of many internal and external factors.Therefore,this paper takes the dam-front Danbo accumulation body landslide of Yangfanggou hydropower station on the Yalong River as the geological prototype,and discusses the process and mechanism of slope stability degradation under the combined action of rainfall and slope construction.Based on the detailed understanding of the basic characteristics of the accumulation body,the development characteristics of the landslide and the construction situation of the slope engineering,the study conducted correlation analysis between rainfall and landslide displacement,the physical and mechanical tests of all types of rocksoil masses,and the numerical simulation testing of seepage field variation of the landslide section.It is found that the special slope structure and material composition of the old landslide accumulation layer on the upper part of the Danbo accumulation body are the internal factors for the occurrence of thrust loadinduced landslide,and the construction of the slope engineering not only creates free space conditions for sliding,but also provides channels for the infiltration of rainfall into the slope after confluence,which is an external factor that caused the mechanical properties of the sliding zone soil to gradually weaken from the trailing edge to the leading edge.The geomechanical model of such landslide is that the active section of the trailing edge produces the"source of force",the transition section of the middle section affects the occurrence of sliding,and the anti-sliding section of the leading edge controls the occurrence of landslide hazards.The results of this research provide not only a useful supplement to the theory of landslide formation mechanisms but also a scientific basis for guiding the prevention and control of similar hazards.
基金support of Russian Science Foundation (Project No.23-17-00148)as a part of R&D project (State registry No.121062200075-4).
文摘The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.
基金by the National Natural Science Foundation of China(Grant No.51991392)the National Natural Science Foundation of China(Grant No.51922104).
文摘Displacement-monitoring-based back analysis is a popular method for geomechanical parameter estimation.However,due to the delayed installation of multi-point extensometers,the monitoring curve is only a part of the overall one,leading to displacement loss.Besides,the monitoring and construction time on the monitoring curve is difficult to determine.In the literature,the final displacement was selected for the back analysis,which could induce unreliable results.In this paper,a displacement-based back analysis method to mitigate the influence of displacement loss is developed.A robust hybrid optimization algorithm is proposed as a substitute for time-consuming numerical simulation.It integrates the strengths of the nonlinear mapping and prediction capability of the support vector machine(SVM)algorithm,the global searching and optimization characteristics of the optimized particle swarm optimization(OPSO)algorithm,and the nonlinear numerical simulation capability of ABAQUS.To avoid being trapped in the local optimum and to improve the efficiency of optimization,the standard PSO algorithm is improved and is compared with other three algorithms(genetic algorithm(GA),simulated annealing(SA),and standard PSO).The results indicate the superiority of OPSO algorithm.Finally,the hybrid optimization algorithm is applied to an engineering project.The back-analyzed parameters are submitted to numerical analysis,and comparison between the calculated and monitoring displacement curve shows that this hybrid algorithm can offer a reasonable reference for geomechanical parameters estimation.
文摘Geomechanics as the knowledge of rock deformation and stability is an indispensable part of all field development plans.Conducting geomechanical analyses leads to a safer and more efficient operation otherwise different kinds of instability and distortion might occur.In this study,the geomechanical behavior of Ilam and Sarvak formations of an oil field in southwest of Iran was investigated.The research objectives can be summarized as wellbore stability evaluation and predicting the value of reservoir subsidence due to pressure drop as a result of reservoir fluid production.To fulfill these,a set of petrophysical logs run in the exploration well of this green field were collected.Next,using empirical correlations and statistical methods,required data for evaluating wellbore stability during drilling,specifying safe mud window to discover reservoir breakdown pressure,predicting the possibility of wellbore collapse in field lifetime,and assessing reservoir subsidence were determined.The results revealed that the average subsidence value as the consequence of production within 21 years is 0.275 ft Which is not significant.In terms of wellbore stability,it was concluded that all horizontal and vertical wells remain stable during this time period.Briefly to conclude,field development is not associated with alarming incidents from geomechanical aspect.
基金provided by the National Energy Technology Laboratory and U.S.DOE,Office of Fossil Energy as part of the National Risk Assessment Partnershipfunded by the U.S.DOE Office of Vehicle Technologies
文摘This work develops a three-dimensional(3D) multiscale model to analyze a complex carbon dioxide(CO_2) faulted reservoir that includes some key geologic features of the San Andreas and nearby faults southwest of the Kimberlina site.The model uses the STOMP-CO2 code for flow modeling that is coupled to the ABAQUS~ finite element package for geomechanical analysis.A 3D ABAQUS~ finite element model is developed that contains a large number of 3D solid elements with two nearly parallel faults whose damage zones and cores are discretized using the same continuum elements.Five zones with different mineral compositions are considered:shale,sandstone,fault damaged sandstone,fault damaged shale,and fault core.Rocks' elastic properties that govern their poroelastic behavior are modeled by an Eshelby-Mori-Tanaka approach(EMTA).which can account for up to 15 mineral phases.The permeability of fault damage zones affected by crack density and orientations is also predicted by an EMTA formulation.A STOMP-CO2 grid that exactly maps the ABAQUS~ finite element model is built for coupled hydromechanical analyses.Simulations of the reservoir assuming three different crack pattern situations(including crack volume fraction and orientation) for the fault damage zones are performed to predict the potential leakage of CO_2 due to cracks that enhance the permeability of the fault damage zones.The results illustrate the important effect of the crack orientation on fault permeability that can lead to substantial leakage along the fault attained by the expansion of the CO_2 plume.Potential hydraulic fracture and tendency for the faults to slip are also examined and discussed in terms of stress distributions and geomechanical properties.
文摘In this paper,the geomechanical impact of large-scale carbon dioxide(CO) storage in depleted Dutch gas fields is compared with the impact of COstorage in saline aquifers.The geomechanical behaviour of four potential COstorage sites is examined using flow and geomechanical simulations.Many gas reservoirs in the Netherlands are found in fault blocks,one to a few kilometres wide,laterally bounded by sealing faults.Aquifer depletion or re-pressurization in the lateral direction is seldom an issue because of a lack of active aquifers.Reservoir pressure changes are therefore limited to a gas-bearing fault block,while the induced stress changes affect the gas reservoir and extend 1-3 km away into the surrounding rock.Arguments in favour of COstorage in depleted gas fields are:proven seal quality,availability of field data,no record of seal integrity failure by fault reactivation from the seismically active producing Dutch gas fields,and the potential benefits of restoring the virgin formation pressure and stress state to geomechanical stability.On the other hand,COinjection in saline aquifers causes pressure build-up that exceeds the virgin hydrostatic pressure.Stress perturbations resulting from pressure build-up affect large areas,extending tens of kilometres away from the injection wells.Induced stresses in top seals are.however,small and do not exceed a few tenths of megapascal for a pressure build-up of a few megapascals in the storage formation.Geomechanical effects on top seals are weak,but could be enhanced close to the injection zone by the thermal effects of injection.Uncertainties related to characterisation of large areas affected by pressure build-up are significant,and seal quality and continuity are more difficult to be demonstrated for aquifers than for depleted gas reservoirs that have held hydrocarbons for millions of years.
