Due to complex geological structures and a narrow safe mud density window,offshore fractured formations frequently encounter severe lost circulation(LC)during drilling,significantly hindering oil and gas exploration a...Due to complex geological structures and a narrow safe mud density window,offshore fractured formations frequently encounter severe lost circulation(LC)during drilling,significantly hindering oil and gas exploration and development.Predicting LC risks enables the targeted implementation of mitigation strategies,thereby reducing the frequency of such incidents.To address the limitations of existing 3D geomechanical modeling in predicting LC,such as arbitrary factor selection,subjective weight assignment,and the inability to achieve pre-drilling prediction along the entire well section,an improved prediction method is proposed.This method integrates multi-source data and incorporates three LC-related sensitivity factors:fracture characteristics,rock brittleness,and in-situ stress conditions.A quantitative risk assessment model for LC is developed by combining the subjective analytic hierarchy process with the objective entropy weight method(EWM)to assign weights.Subsequently,3D geomechanical modeling is applied to identify regional risk zones,enabling digital visualization for pre-drilling risk prediction.The developed 3D LC risk prediction model was validated using actual LC incidents from drilled wells.Results were generally consistent with field-identified LC zones,with an average relative error of 19.08%,confirming its reliability.This method provides practical guidance for mitigating potential LC risks and optimizing drilling program designs in fractured formations.展开更多
One of the pathways to attain NET ZERO is CO_(2)injection into deep saline aquifers(DSAs),which alters the saturation and pore pressure of the reservoir rocks,hence the effective stress,sʹ.This,in turn,would change th...One of the pathways to attain NET ZERO is CO_(2)injection into deep saline aquifers(DSAs),which alters the saturation and pore pressure of the reservoir rocks,hence the effective stress,sʹ.This,in turn,would change their geomechanical(i.e.peak deviatoric stress,elastic modulus,Poisson's ratio)and petrophysical(porosity and permeability)properties.Such a situation might trigger geo-hazards,like induced seismicity,ground deformation,caprock failure.Hence,reducing the risk of such hazards necessitates quantifying the spatial and temporal changes in sʹ,under specific CO_(2)and/or brine saturation,designated as S_(CO2)and S_(b),respectively,and resultant pore pressure.With this in view,a conceptual model depicting the reservoir,demarcated by five zones based on variations in saturation,pore-pressure,temperature,etc.,and the corresponding effective stress equations have been proposed based on the available literature.Furthermore,a critical review of literature has been carried out to decipher the limitations and contradictions associated with the findings from(i)laboratory studies to estimate S_(CO2)employing pwave velocity and electrical resistivity,(ii)analytical and numerical approaches for estimating the variation of pore-pressure in the reservoir rocks,and(iii)laboratory studies on variation in geomechanical and petrophysical properties under the conditions representative of the above-mentioned zones of the conceptual model.The authors consider that extensive experiments should be conducted on the rocks from different sources and tested under various conditions of the CO_(2)injection to validate the proposed model for the execution of risk-free CO_(2)storage in DSAs.展开更多
Reservoir evaluation is important in identifying oil and gas sweet spots in sedimentary basins.This also holds true in the Tarim Basin,where the ultra-deep oil and gas-bearing formations have high present-day in situ ...Reservoir evaluation is important in identifying oil and gas sweet spots in sedimentary basins.This also holds true in the Tarim Basin,where the ultra-deep oil and gas-bearing formations have high present-day in situ stress and geothermal temperature in addition to their considerable depth as a result of multiple stages of tectonic evolution.Traditional reservoir evaluation methods are based mainly on analyses of reservoir parameters like porosity,permeability,and pore throat structure;these parameters can sometimes vary dramatically in areas with complex Structures.Geomechanics-based reservoir evaluations are favored as they adequately capture the impact of tectonic processes on reservoirs,especially those in the Tarim Basin.This study evaluates the ultra-deep clastic reservoirs in the Kuqa Depression of the Tarim Basin by integrating the geomechanical parameters including elastic modulus,natural fracture density,and present-day in situ stress into a 3D geological modeling-based reservoir evaluation.The entropy weight method is introduced to establish a comprehensive index(Q)for reservoir evaluation.The results show that the positive correlation of the daily gas production rate of representative wells in the study area with this indicator is an effective way of reservoir evaluation in ultra-deep areas with complex structures.展开更多
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
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
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
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
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
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
Among the methods used for evaluating the potential hydraulic erodibility of rock,the most common methods are those based on the correlation between the force of flowing water and the capacity of a rock to resist eros...Among the methods used for evaluating the potential hydraulic erodibility of rock,the most common methods are those based on the correlation between the force of flowing water and the capacity of a rock to resist erosion,such as Annandale’s and Pells’methods.The capacity of a rock to resist erosion is evaluated based on erodibility indices that are determined from specific geomechanical parameters of a rock mass.These indices include unconfined compressive strength(UCS)of rock,rock block size,joint shear strength,a block’s shape and orientation relative to the direction of flow,joint openings,and the nature of the surface to be potentially eroded.However,it is difficult to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock.The assessment of eroded unlined spillways of dams has shown that the capacity of a rock to resist erosion is not accurately evaluated.Using more than 100 case studies,we develop a method to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock in unlined spillways.The UCS of rock is found not to be a relevant parameter for evaluating the hydraulic erodibility of rock.On the other hand,we find that the use of three-dimensional(3D)block volume measurements,instead of the block size factor used in Annandale’s method,improves the rock block size estimation.Furthermore,the parameter representing the effect of a rock block’s shape and orientation relative to the direction of flow,as considered in Pells’method,is more accurate than the parameter adopted by Annandale’s method.展开更多
This paper tries to characterize volcanic rocks through the development and application of an empirical geomechanical system. Geotechnical information was collected from the samples from several Atlantic Ocean islands...This paper tries to characterize volcanic rocks through the development and application of an empirical geomechanical system. Geotechnical information was collected from the samples from several Atlantic Ocean islands including Madeira, Azores and Canarias archipelagos. An empirical rock classification system termed as the volcanic rock system(VRS) is developed and presented in detail. Results using the VRS are compared with those obtained using the traditional rock mass rating(RMR) system. Data mining(DM) techniques are applied to a database of volcanic rock geomechanical information from the islands.Different algorithms were developed and consequently approaches were followed for predicting rock mass classes using the VRS and RMR classification systems. Finally, some conclusions are drawn with emphasis on the fact that a better performance was achieved using attributes from VRS.展开更多
Understanding and predicting the distribution of fractures in the deep tight sandstone reservoir are important for both gas exploration and exploitation activities in Kuqa Depression. We analyzed the characteristics o...Understanding and predicting the distribution of fractures in the deep tight sandstone reservoir are important for both gas exploration and exploitation activities in Kuqa Depression. We analyzed the characteristics of regional structural evolution and paleotectonic stress setting based on acoustic emission tests and structural feature analysis. Several suites of geomechanical models and experiments were developed to analyze how the geological factors influenced and controlled the development and distribution of fractures during folding. The multilayer model used elasto-plastic finite element method to capture the stress variations and slip along bedding surfaces, and allowed large deformation. The simulated results demonstrate that this novel Quasi-Binary Method coupling composite failure criterion and geomechanical model can effectively quantitatively predict the developed area of fracture parameters in fault-related folds. High-density regions of fractures are mainly located in the fold limbs during initial folding stage, then gradually migrate from forelimb to backlimb, from limbs to hinge, from deep to shallow along with the fold uplift. Among these factors, the fold uplift and slip displacement along fault have the most important influence on distributions of fractures and stress field, meanwhile the lithology and distance to fault have also has certain influences. When the uplift height exceeds approximately 55 percent of the total height of fold the facture density reaches a peak, which conforms to typical top-graben fold type with large amplitude and high-density factures in the top. The overall simulated results match well with core observation and FMI results both in the whole geometry and fracture distribution.展开更多
Xigeda formation is a type of hundredmeter-thick lacustrine sediments of being prone to triggering landslides along the trunk channel and tributaries of the upper Yangtze River in China. The Yonglang landslide located...Xigeda formation is a type of hundredmeter-thick lacustrine sediments of being prone to triggering landslides along the trunk channel and tributaries of the upper Yangtze River in China. The Yonglang landslide located near Yonglang Town of Dechang County in Sichuan Province of China, which was a typical Xigeda formation landslide, was stabilized by anti-slide piles. Loading tests on a loading-test pile were conducted to measure the displacements and moments. The uncertainty of the tested geomechanical parameters of the Yonglang landslide over certain ranges would be problematic during the evaluation of the landslide. Thus, uniform design was introduced in the experimental design,and by which, numerical analyses of the loading-test pile were performed using Fast Lagrangian Analysis of Continua(FLAC3D) to acquire a database of the geomechanical parameters of the Yonglang landslide and the corresponding displacements of the loadingtest pile. A three-layer back-propagation neural network was established and trained with the database, and then tested and verified for its accuracy and reliability in numerical simulations. Displacement back analysis was conducted by substituting the displacements of the loading-test pile to the well-trained three-layer back-propagation neural network so as to identify the geomechanical parameters of the Yonglang landslide. The neuralnetwork-based displacement back analysis method with the proposed methodology is verified to be accurate and reliable for the identification of the uncertain geomechanical parameters of landslides.展开更多
New technologies are in urgent need of unconventional hydrocarbon exploration and development in China.This paper provides a brief introduction and analysis of a new three-dimensional(3D)geomechanical restoration meth...New technologies are in urgent need of unconventional hydrocarbon exploration and development in China.This paper provides a brief introduction and analysis of a new three-dimensional(3D)geomechanical restoration method developed in recent years.After an in-depth discussion on the technical principle and specific characteristics of the fields,we designed a feasible workflow for two oil-gas fields with great unconventional oil-gas resource potentials in China(Weiyuan and Jiulongshan oil-gas fields of Sichuan).After discussing the major challenges and limitations of the new technology,we also suggest its research efforts and future application prospect It is shown that the new technology will be an effective method to facilitate the exploration and development of unconventional oil and gas resources in China.展开更多
In Senegal, rock mechanic studies began in last four years and were a very new engineering domain. So, the first stage is to characterize geological materials. It is on this way that this work is done. This paper anal...In Senegal, rock mechanic studies began in last four years and were a very new engineering domain. So, the first stage is to characterize geological materials. It is on this way that this work is done. This paper analyzes geomechanical parameters of sandstones of Dindifélo and basalt of Bafoundou belonging to the Proterozoic rocks domain of eastern Senegal. By Rock Mass Rating (RMR) and Geological Strength Index (GSI), sandstones of the Dindifello Cliff show fair to poor characteristics while basalts of the hills of Bafoundou are fair quality. In addition to the qualities of rock mass, Young moduli, uniaxial compressive strengths and tensile strength of rock mass are also defined using Rock Quality Designation (RQD) GSI, RMR. Hoek-Brown parameters m and a, depend both on the fracturation and the content fine in the rock. Values of mechanical parameters are different when deduced from RMR, GSI and from intact rock laboratory test. Those differences are due to variables taken account. The variation depends also on the quality of the rock. Statistical analysis shows possible unstabilities which depend on rock mass parameters but with acceptable probability of failure. Probability of failure is the highest when deducing from Mohr criterion than from Hoek-Brown criterion.展开更多
Large amounts of carbon dioxide(CO2) should be injected in deep saline formations to mitigate climate change,implying geomechanical challenges that require further understanding.Pressure build-up induced by CO2injecti...Large amounts of carbon dioxide(CO2) should be injected in deep saline formations to mitigate climate change,implying geomechanical challenges that require further understanding.Pressure build-up induced by CO2injection will decrease the effective stresses and may affect fault stability.Geomechanical effects of overpressure induced by CO2injection either in the hanging wall or in the foot wall on fault stability are investigated.CO2injection in the presence of a low-permeable fault induces pressurization of the storage formation between the injection well and the fault.The low permeability of the fault hinders fluid flow across it and leads to smaller overpressure on the other side of the fault.This variability in the fluid pressure distribution gives rise to differential total stress changes around the fault that reduce its stability.Despite a significant pressure build-up induced by the fault,caprock stability around the injection well is not compromised and thus,CO2leakage across the caprock is unlikely to happen.The decrease in fault stability is similar regardless of the side of the fault where CO2is injected.Simulation results show that fault core permeability has a significant effect on fault stability,becoming less affected for high-permeable faults.An appropriate pressure management will allow storing large quantities of CO2without inducing fault reactivation.展开更多
To reduce the emissions of carbon dioxide(CO) into the atmosphere, it is proposed to inject anthropogenic COinto deep geological formations. Deep un-mineable coalbeds are considered to be possible COrepositories becau...To reduce the emissions of carbon dioxide(CO) into the atmosphere, it is proposed to inject anthropogenic COinto deep geological formations. Deep un-mineable coalbeds are considered to be possible COrepositories because coal is able to adsorb a large amount of COinside its microporous structure.However, the response of coalbeds is complex because of coupled flow and mechanical processes. Injection of COcauses coal to swell, which leads to reductions in permeability and hence makes injection more difficult, and at the same time leads to changes in the mechanical properties which can affect the stress state in the coal and overlying strata. The mechanical properties of coal under storage conditions are of importance when assessing the integrity and safety of the storage scheme. On the other hand, the geomechanical response of coalbed will also influence the reservoir performance of coalbed. This paper provides an overview of processes associated with coalbed geosequestration of COwhile the importance of geomechanical characteristics of coalbeds is highlighted. The most recent findings about the interactions between gas transport and geomechanical characteristics of coal will be discussed and the essence will be delivered. The author suggests areas for future research efforts to further improve the understanding of enhanced coalbed methane(ECBM) and coalbed geosequestration of CO.展开更多
We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled sim...We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress,which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load.The elongate reservoir displays significant stress asymmetry,with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link betweenstress path parameters and seismic anisotropy is complex,where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models.展开更多
Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress env...Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress environment in which these are propagating.However,spatial and stratigraphic variations in the stress and geomechanical properties of shales make accurate modelling a challenging task.For the UK Bowland Shale,stacked horizontal wells targeting multiple stratigraphic intervals could be used to avoid large offset faults in a geologically complex area.However,it is not known how these intervals may respond to hydraulic fracturing and predicting the height and length of hydraulic fractures is necessary in order to assess the likelihood of vertical fracture interference across landing zones or propagation towards major faults.In the case of the former,intervals of high effective stress may be key to containing fractures within their desired target.Using a planar hydraulic fracture simulator,and a 3D geomechanical model incorporating dipping stratigraphy,the issue of predicting hydraulic fracture geometry in the Bowland Shale was assessed through a series of modelling exercises using well Preese Hall-1 and horizontal pseudo-wells.When pre-defined landing zones were targeted,narrow and long transverse fractures around 1 km from the well were simulated.When the simulation design mimicked perforation clusters placed at 12 m intervals along horizontal pseudo-wells,the effects of stress shadowing were acute and resulted in irregular fracture geometries.Furthermore,high effective stress intervals performed efficiently as barriers to vertical hydraulic fracture propagation,reinforcing the feasibility of using stacked production for the Bowland Shale.The modelling results were then used to discuss the possible placement of horizontal wells in a mapped,100 km2 region around well Preese Hall-1,where up to 13 sites could be positioned,with a horizontal well length of around 1.5 km.Finally,by drawing on a wellestablished analogue for the Bowland Shale,it was estimated that up to 195 Bcf of gas could be produced from the 13 locations in the area if three stratigraphic intervals are produced from one location.展开更多
The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties ...The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties in the Central Appalachian Basin.Geomechanical properties of the Rose Run sandstone(upper Ordovician Knox group)were tested for its suitability as a storage reservoir.A 9.8-m thick section of the Rose Run was penetrated at 1000 m drilled depth and a whole-diameter core and rotary sidewall cores were taken.Average porosity and permeability measured in core plugs were 9.1%and 44.6 mD,respectively.Maximum vertical stress gradient calculated in the wellbore was 26 MPa/km.Wellbore fractures in dolomites underlying and overlying the Rose Run follow the contemporary N53E Appalachian Basin stress field.The Rose Run elastic geomechanical properties were calibrated to values measured in core plugs to evaluate its fracturing risk as a CO2 storage reservoir.Mean Young’s modulus and Poisson’s ratio values of the Rose Run were 45 GPa and 0.23,respectively,whereas Young’s modulus and Poisson’s ratio values were 77.1 GPa and 0.28,respectively,in the overlying Beekmantown dolomite,suggesting the Rose Run may fracture if overpressured during CO2 injection but be confined by the Beekmantown.Triaxial compressive strength measured in core plugs found the Rose Run and Beekmantown fractured at mean axial stresses of 156.5 MPa and 282.2 MPa,respectively,confirming the Beekmantown as suitable for confining CO2 injected into the Rose Run.A step-rate test was conducted in a mechanically-isolated 18.6-m interval bracketing the Rose Run.Static Rose Run reservoir pressure was 9.3 MPa,and fracture gradient under injection was 13.6 MPa/km,suggesting step-rate testing before CO2 injection,and subsequent pressure monitoring to ensure confinement.As the region around the KGS 1 Hanson Aggregates well is underpressured and adjacent to faulted Precambrian basement,further research is needed to evaluate its induced seismicity risk during CO2 injection.展开更多
基金supported by the National Natural Science Foundation of China(No.52074312)the CNPC Science and Technology Innovation Foundation(No.2021DQ02-0505)+1 种基金the Open Fund Project of the National Key Laboratory for the Enrichment Mechanism and Efficient Development of Shale Oil and Gas(No.36650000-24-ZC0609-0006)the Major Science and Technology Project of Karamay City(No.20232023zdzx0003).
文摘Due to complex geological structures and a narrow safe mud density window,offshore fractured formations frequently encounter severe lost circulation(LC)during drilling,significantly hindering oil and gas exploration and development.Predicting LC risks enables the targeted implementation of mitigation strategies,thereby reducing the frequency of such incidents.To address the limitations of existing 3D geomechanical modeling in predicting LC,such as arbitrary factor selection,subjective weight assignment,and the inability to achieve pre-drilling prediction along the entire well section,an improved prediction method is proposed.This method integrates multi-source data and incorporates three LC-related sensitivity factors:fracture characteristics,rock brittleness,and in-situ stress conditions.A quantitative risk assessment model for LC is developed by combining the subjective analytic hierarchy process with the objective entropy weight method(EWM)to assign weights.Subsequently,3D geomechanical modeling is applied to identify regional risk zones,enabling digital visualization for pre-drilling risk prediction.The developed 3D LC risk prediction model was validated using actual LC incidents from drilled wells.Results were generally consistent with field-identified LC zones,with an average relative error of 19.08%,confirming its reliability.This method provides practical guidance for mitigating potential LC risks and optimizing drilling program designs in fractured formations.
基金The authors would like to acknowledge the grant of fellowship(DST/TMD/EWO/2K21/ACT/2021/02(G))under Project SHARP,received from the Department of Science and Technology,Government of India.
文摘One of the pathways to attain NET ZERO is CO_(2)injection into deep saline aquifers(DSAs),which alters the saturation and pore pressure of the reservoir rocks,hence the effective stress,sʹ.This,in turn,would change their geomechanical(i.e.peak deviatoric stress,elastic modulus,Poisson's ratio)and petrophysical(porosity and permeability)properties.Such a situation might trigger geo-hazards,like induced seismicity,ground deformation,caprock failure.Hence,reducing the risk of such hazards necessitates quantifying the spatial and temporal changes in sʹ,under specific CO_(2)and/or brine saturation,designated as S_(CO2)and S_(b),respectively,and resultant pore pressure.With this in view,a conceptual model depicting the reservoir,demarcated by five zones based on variations in saturation,pore-pressure,temperature,etc.,and the corresponding effective stress equations have been proposed based on the available literature.Furthermore,a critical review of literature has been carried out to decipher the limitations and contradictions associated with the findings from(i)laboratory studies to estimate S_(CO2)employing pwave velocity and electrical resistivity,(ii)analytical and numerical approaches for estimating the variation of pore-pressure in the reservoir rocks,and(iii)laboratory studies on variation in geomechanical and petrophysical properties under the conditions representative of the above-mentioned zones of the conceptual model.The authors consider that extensive experiments should be conducted on the rocks from different sources and tested under various conditions of the CO_(2)injection to validate the proposed model for the execution of risk-free CO_(2)storage in DSAs.
基金founded by China National Petroleum Corporation Major Science and Technology Project“Research and Application of Key Technologies for the Development of Ultra-Deep Oil and Gas Reservoirs”(2023ZZ14-03).
文摘Reservoir evaluation is important in identifying oil and gas sweet spots in sedimentary basins.This also holds true in the Tarim Basin,where the ultra-deep oil and gas-bearing formations have high present-day in situ stress and geothermal temperature in addition to their considerable depth as a result of multiple stages of tectonic evolution.Traditional reservoir evaluation methods are based mainly on analyses of reservoir parameters like porosity,permeability,and pore throat structure;these parameters can sometimes vary dramatically in areas with complex Structures.Geomechanics-based reservoir evaluations are favored as they adequately capture the impact of tectonic processes on reservoirs,especially those in the Tarim Basin.This study evaluates the ultra-deep clastic reservoirs in the Kuqa Depression of the Tarim Basin by integrating the geomechanical parameters including elastic modulus,natural fracture density,and present-day in situ stress into a 3D geological modeling-based reservoir evaluation.The entropy weight method is introduced to establish a comprehensive index(Q)for reservoir evaluation.The results show that the positive correlation of the daily gas production rate of representative wells in the study area with this indicator is an effective way of reservoir evaluation in ultra-deep areas with complex structures.
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.
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.
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.
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the Natural Sciences and Engineering Research Council of Canada(Grant No.498020-16)Hydro-Quebec(NC525700)the Mitacs Accelerate Program(Grant Ref.IT10008)
文摘Among the methods used for evaluating the potential hydraulic erodibility of rock,the most common methods are those based on the correlation between the force of flowing water and the capacity of a rock to resist erosion,such as Annandale’s and Pells’methods.The capacity of a rock to resist erosion is evaluated based on erodibility indices that are determined from specific geomechanical parameters of a rock mass.These indices include unconfined compressive strength(UCS)of rock,rock block size,joint shear strength,a block’s shape and orientation relative to the direction of flow,joint openings,and the nature of the surface to be potentially eroded.However,it is difficult to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock.The assessment of eroded unlined spillways of dams has shown that the capacity of a rock to resist erosion is not accurately evaluated.Using more than 100 case studies,we develop a method to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock in unlined spillways.The UCS of rock is found not to be a relevant parameter for evaluating the hydraulic erodibility of rock.On the other hand,we find that the use of three-dimensional(3D)block volume measurements,instead of the block size factor used in Annandale’s method,improves the rock block size estimation.Furthermore,the parameter representing the effect of a rock block’s shape and orientation relative to the direction of flow,as considered in Pells’method,is more accurate than the parameter adopted by Annandale’s method.
文摘This paper tries to characterize volcanic rocks through the development and application of an empirical geomechanical system. Geotechnical information was collected from the samples from several Atlantic Ocean islands including Madeira, Azores and Canarias archipelagos. An empirical rock classification system termed as the volcanic rock system(VRS) is developed and presented in detail. Results using the VRS are compared with those obtained using the traditional rock mass rating(RMR) system. Data mining(DM) techniques are applied to a database of volcanic rock geomechanical information from the islands.Different algorithms were developed and consequently approaches were followed for predicting rock mass classes using the VRS and RMR classification systems. Finally, some conclusions are drawn with emphasis on the fact that a better performance was achieved using attributes from VRS.
文摘Understanding and predicting the distribution of fractures in the deep tight sandstone reservoir are important for both gas exploration and exploitation activities in Kuqa Depression. We analyzed the characteristics of regional structural evolution and paleotectonic stress setting based on acoustic emission tests and structural feature analysis. Several suites of geomechanical models and experiments were developed to analyze how the geological factors influenced and controlled the development and distribution of fractures during folding. The multilayer model used elasto-plastic finite element method to capture the stress variations and slip along bedding surfaces, and allowed large deformation. The simulated results demonstrate that this novel Quasi-Binary Method coupling composite failure criterion and geomechanical model can effectively quantitatively predict the developed area of fracture parameters in fault-related folds. High-density regions of fractures are mainly located in the fold limbs during initial folding stage, then gradually migrate from forelimb to backlimb, from limbs to hinge, from deep to shallow along with the fold uplift. Among these factors, the fold uplift and slip displacement along fault have the most important influence on distributions of fractures and stress field, meanwhile the lithology and distance to fault have also has certain influences. When the uplift height exceeds approximately 55 percent of the total height of fold the facture density reaches a peak, which conforms to typical top-graben fold type with large amplitude and high-density factures in the top. The overall simulated results match well with core observation and FMI results both in the whole geometry and fracture distribution.
基金supported by the "Light of West China" Program of Chinese Academy of Sciences (Grant No.Y6R2250250)the National Basic Research Program of China (973 Program, Grant No.2013CB733201)+2 种基金the One-Hundred Talents Program of Chinese Academy of Sciences (LijunSu)the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant No.QYZDB-SSW-DQC010)the Youth Fund of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences (Grant No. Y6K2110110)
文摘Xigeda formation is a type of hundredmeter-thick lacustrine sediments of being prone to triggering landslides along the trunk channel and tributaries of the upper Yangtze River in China. The Yonglang landslide located near Yonglang Town of Dechang County in Sichuan Province of China, which was a typical Xigeda formation landslide, was stabilized by anti-slide piles. Loading tests on a loading-test pile were conducted to measure the displacements and moments. The uncertainty of the tested geomechanical parameters of the Yonglang landslide over certain ranges would be problematic during the evaluation of the landslide. Thus, uniform design was introduced in the experimental design,and by which, numerical analyses of the loading-test pile were performed using Fast Lagrangian Analysis of Continua(FLAC3D) to acquire a database of the geomechanical parameters of the Yonglang landslide and the corresponding displacements of the loadingtest pile. A three-layer back-propagation neural network was established and trained with the database, and then tested and verified for its accuracy and reliability in numerical simulations. Displacement back analysis was conducted by substituting the displacements of the loading-test pile to the well-trained three-layer back-propagation neural network so as to identify the geomechanical parameters of the Yonglang landslide. The neuralnetwork-based displacement back analysis method with the proposed methodology is verified to be accurate and reliable for the identification of the uncertain geomechanical parameters of landslides.
文摘New technologies are in urgent need of unconventional hydrocarbon exploration and development in China.This paper provides a brief introduction and analysis of a new three-dimensional(3D)geomechanical restoration method developed in recent years.After an in-depth discussion on the technical principle and specific characteristics of the fields,we designed a feasible workflow for two oil-gas fields with great unconventional oil-gas resource potentials in China(Weiyuan and Jiulongshan oil-gas fields of Sichuan).After discussing the major challenges and limitations of the new technology,we also suggest its research efforts and future application prospect It is shown that the new technology will be an effective method to facilitate the exploration and development of unconventional oil and gas resources in China.
文摘In Senegal, rock mechanic studies began in last four years and were a very new engineering domain. So, the first stage is to characterize geological materials. It is on this way that this work is done. This paper analyzes geomechanical parameters of sandstones of Dindifélo and basalt of Bafoundou belonging to the Proterozoic rocks domain of eastern Senegal. By Rock Mass Rating (RMR) and Geological Strength Index (GSI), sandstones of the Dindifello Cliff show fair to poor characteristics while basalts of the hills of Bafoundou are fair quality. In addition to the qualities of rock mass, Young moduli, uniaxial compressive strengths and tensile strength of rock mass are also defined using Rock Quality Designation (RQD) GSI, RMR. Hoek-Brown parameters m and a, depend both on the fracturation and the content fine in the rock. Values of mechanical parameters are different when deduced from RMR, GSI and from intact rock laboratory test. Those differences are due to variables taken account. The variation depends also on the quality of the rock. Statistical analysis shows possible unstabilities which depend on rock mass parameters but with acceptable probability of failure. Probability of failure is the highest when deducing from Mohr criterion than from Hoek-Brown criterion.
基金the support from the"EPFL Fellows"fellowship program co-funded by Marie Curie,FP7(Grant No.291771)partial support from the"TRUST"project of the European Community's Seventh Framework Programme FP7/2007-2013(Grant No.309607)+2 种基金the"FracRisk"project of the European Community's Horizon 2020 Framework Programme H2020-EU.3.3.2.3(Grant No.640979)sponsored by SCCER-SoE(Switzerland)(Grant No.KTI.2013.288)Swiss Federal Office of Energy(SFOE)project CAPROCK(Grant No.810008154)
文摘Large amounts of carbon dioxide(CO2) should be injected in deep saline formations to mitigate climate change,implying geomechanical challenges that require further understanding.Pressure build-up induced by CO2injection will decrease the effective stresses and may affect fault stability.Geomechanical effects of overpressure induced by CO2injection either in the hanging wall or in the foot wall on fault stability are investigated.CO2injection in the presence of a low-permeable fault induces pressurization of the storage formation between the injection well and the fault.The low permeability of the fault hinders fluid flow across it and leads to smaller overpressure on the other side of the fault.This variability in the fluid pressure distribution gives rise to differential total stress changes around the fault that reduce its stability.Despite a significant pressure build-up induced by the fault,caprock stability around the injection well is not compromised and thus,CO2leakage across the caprock is unlikely to happen.The decrease in fault stability is similar regardless of the side of the fault where CO2is injected.Simulation results show that fault core permeability has a significant effect on fault stability,becoming less affected for high-permeable faults.An appropriate pressure management will allow storing large quantities of CO2without inducing fault reactivation.
文摘To reduce the emissions of carbon dioxide(CO) into the atmosphere, it is proposed to inject anthropogenic COinto deep geological formations. Deep un-mineable coalbeds are considered to be possible COrepositories because coal is able to adsorb a large amount of COinside its microporous structure.However, the response of coalbeds is complex because of coupled flow and mechanical processes. Injection of COcauses coal to swell, which leads to reductions in permeability and hence makes injection more difficult, and at the same time leads to changes in the mechanical properties which can affect the stress state in the coal and overlying strata. The mechanical properties of coal under storage conditions are of importance when assessing the integrity and safety of the storage scheme. On the other hand, the geomechanical response of coalbed will also influence the reservoir performance of coalbed. This paper provides an overview of processes associated with coalbed geosequestration of COwhile the importance of geomechanical characteristics of coalbeds is highlighted. The most recent findings about the interactions between gas transport and geomechanical characteristics of coal will be discussed and the essence will be delivered. The author suggests areas for future research efforts to further improve the understanding of enhanced coalbed methane(ECBM) and coalbed geosequestration of CO.
基金the sponsors of the IPEGG project, BG, BP, Statoilthe Research Council UK (EP/K035878/1+1 种基金 EP/K021869/1 NE/L000423/1) for financial support
文摘We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress,which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load.The elongate reservoir displays significant stress asymmetry,with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link betweenstress path parameters and seismic anisotropy is complex,where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models.
基金a James Watt Scholarship from Heriot-Watt University(HWU)and the receipt of a British University Funding Initiative(BUFI)studentship award(grant number GA/16S/024)from the British Geological Survey(BGS)which provides the funding for the PhD project upon which this work is based.The PhD forms part of the Natural Environment Research Council(NERC)Centre for Doctoral Training(CDT)in Oil and Gas(grant number NE/M00578X/1)The BGS is thanked for providing access to well data,Schlumberger are thanked for the provision of Techlog software and Halliburton are thanked for the provision of GOHFER software under academic license to HWU.Jingsheng Ma acknowledges NERC grant number NE/R018022/1 for financial support.
文摘Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress environment in which these are propagating.However,spatial and stratigraphic variations in the stress and geomechanical properties of shales make accurate modelling a challenging task.For the UK Bowland Shale,stacked horizontal wells targeting multiple stratigraphic intervals could be used to avoid large offset faults in a geologically complex area.However,it is not known how these intervals may respond to hydraulic fracturing and predicting the height and length of hydraulic fractures is necessary in order to assess the likelihood of vertical fracture interference across landing zones or propagation towards major faults.In the case of the former,intervals of high effective stress may be key to containing fractures within their desired target.Using a planar hydraulic fracture simulator,and a 3D geomechanical model incorporating dipping stratigraphy,the issue of predicting hydraulic fracture geometry in the Bowland Shale was assessed through a series of modelling exercises using well Preese Hall-1 and horizontal pseudo-wells.When pre-defined landing zones were targeted,narrow and long transverse fractures around 1 km from the well were simulated.When the simulation design mimicked perforation clusters placed at 12 m intervals along horizontal pseudo-wells,the effects of stress shadowing were acute and resulted in irregular fracture geometries.Furthermore,high effective stress intervals performed efficiently as barriers to vertical hydraulic fracture propagation,reinforcing the feasibility of using stacked production for the Bowland Shale.The modelling results were then used to discuss the possible placement of horizontal wells in a mapped,100 km2 region around well Preese Hall-1,where up to 13 sites could be positioned,with a horizontal well length of around 1.5 km.Finally,by drawing on a wellestablished analogue for the Bowland Shale,it was estimated that up to 195 Bcf of gas could be produced from the 13 locations in the area if three stratigraphic intervals are produced from one location.
基金the Commonwealth of Kentucky,USA through the Energy Independence and Incentives Act of 2007the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,China(Grant No.Z018004).
文摘The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties in the Central Appalachian Basin.Geomechanical properties of the Rose Run sandstone(upper Ordovician Knox group)were tested for its suitability as a storage reservoir.A 9.8-m thick section of the Rose Run was penetrated at 1000 m drilled depth and a whole-diameter core and rotary sidewall cores were taken.Average porosity and permeability measured in core plugs were 9.1%and 44.6 mD,respectively.Maximum vertical stress gradient calculated in the wellbore was 26 MPa/km.Wellbore fractures in dolomites underlying and overlying the Rose Run follow the contemporary N53E Appalachian Basin stress field.The Rose Run elastic geomechanical properties were calibrated to values measured in core plugs to evaluate its fracturing risk as a CO2 storage reservoir.Mean Young’s modulus and Poisson’s ratio values of the Rose Run were 45 GPa and 0.23,respectively,whereas Young’s modulus and Poisson’s ratio values were 77.1 GPa and 0.28,respectively,in the overlying Beekmantown dolomite,suggesting the Rose Run may fracture if overpressured during CO2 injection but be confined by the Beekmantown.Triaxial compressive strength measured in core plugs found the Rose Run and Beekmantown fractured at mean axial stresses of 156.5 MPa and 282.2 MPa,respectively,confirming the Beekmantown as suitable for confining CO2 injected into the Rose Run.A step-rate test was conducted in a mechanically-isolated 18.6-m interval bracketing the Rose Run.Static Rose Run reservoir pressure was 9.3 MPa,and fracture gradient under injection was 13.6 MPa/km,suggesting step-rate testing before CO2 injection,and subsequent pressure monitoring to ensure confinement.As the region around the KGS 1 Hanson Aggregates well is underpressured and adjacent to faulted Precambrian basement,further research is needed to evaluate its induced seismicity risk during CO2 injection.
