In this study,we numerically investigate the influence of hysteretic stress path behavior on the seal integrity during underground gas storage operations in a depleted reservoir.Our study area is the Honor Rancho Unde...In this study,we numerically investigate the influence of hysteretic stress path behavior on the seal integrity during underground gas storage operations in a depleted reservoir.Our study area is the Honor Rancho Underground Storage Facility in Los Angeles County(California,USA),which was converted into an underground gas storage facility in 1975 after 20 years of oil and gas production.In our simulations,the geomechanical behavior of the sand reservoir is modeled using two models:(1)a linear elastic model(non-hysteretic stress path)that does not take into consideration irreversible deformation,and(2)a plastic cap mechanical model which considers changes in rock elastic properties due to irreversible deformations caused by plastic reservoir compaction(hysteretic stress path).It shows that the irreversible compaction of the geological layer over geologic time and during the reservoir depletion can have important consequences on stress tensor orientation and magnitude.Ignoring depletion-induced irreversible compaction can lead to an over-estimation of the calculation of the maximum working reservoir pressure.Moreover,this irreversible compaction may bring the nearby faults closer to reactivation.However,regardless of the two models applied,the geomechanical analysis shows that for the estimated stress conditions applied in this study,the Honor Rancho Underground Storage Facility is being safely operated at pressures much below what would be required to compromise the seal integrity.展开更多
Carbon capture and storage(CCS) in geologic formations has been recognized as a promising option for reducing carbon dioxide(CO) emissions from large stationary sources.However,the pressure buildup inside the storage ...Carbon capture and storage(CCS) in geologic formations has been recognized as a promising option for reducing carbon dioxide(CO) emissions from large stationary sources.However,the pressure buildup inside the storage formation can potentially induce slip along preexisting faults,which could lead to felt seismic ground motion and also provide pathways for brine/COleakage into shallow drinking water aquifers.To assess the geomechanical stability of faults,it is of crucial importance to know the in situ state of stress.In situ stress measurements can provide some information on the stresses acting on faults but with considerable uncertainties.In this paper,we investigate how such uncertainties,as defined by the variation of stress measurements obtained within the study area,could influence the assessment of the geomechanical stability of faults and the characteristics of potential injection-induced seismic events.Our modeling study is based on a hypothetical industrial-scale carbon sequestration project assumed to be located in the Southern San Joaquin Basin in California,USA.We assess the stability on the major(25 km long) fault that bounds the sequestration site and is subjected to significant reservoir pressure changes as a result of 50 years of COinjection.We present a series of geomechanical simulations in which the resolved stresses on the fault were varied over ranges of values corresponding to various stress measurements performed around the study area.The simulation results are analyzed by a statistical approach.Our main results are that the variations in resolved stresses as defined by the range of stress measurements had a negligible effect on the prediction of the seismic risk(maximum magnitude),but an important effect on the timing,the seismicity rate(number of seismic events) and the location of seismic activity.展开更多
The Asmari Formation in the G oilfield on the Iran-Iraq border is a fractured-porous multi-lithology mixed reservoir, for which fracture is an important factor affecting oil productivity and water cut. The characteriz...The Asmari Formation in the G oilfield on the Iran-Iraq border is a fractured-porous multi-lithology mixed reservoir, for which fracture is an important factor affecting oil productivity and water cut. The characterization and modeling of fractures in the carbonate reservoir of G oilfield are challenging due to weak conventional well log responses of fractures and a lack of specific logs, such as image logs. This study proposes an integrated approach for characterizing and modeling fractures in the carbonate reservoir. The features, formation mechanism, influencing factors, and prediction methods of fractures in the Asmari Formation carbonate reservoirs of G oilfield were studied using core observation, thin section, image log, cross-dipole acoustic log (CDAL), geomechanics numerical simulation (GNS), and production data. According to CDAL-based fracture density interpretation, GNS-based fracture intensity prediction between wells, and DFN-based rock fracture properties modeling, the quantitative fracture characterization for G oilfield was realized. This research shows that the fractures in the Asamri Formation are mainly medium-to high-angle shear fractures. The substantial compression stress during the Miocene played a major role in the formation of the prominent fractures and determined their trend in the region, with primary trends of NNW-SSE and NNE-SSW. The fracture distribution has regularity, and the fractures in zone A dolomites are more highly developed than that in zone B limestones vertically. Horizontally, fractures intensity is mainly controlled by faults and structural location. The results of this study may benefit the optimization of well design during field development. From 2019 to 2021, three horizontal wells pilot tests were deployed in the fractures belt in zone A, and these fractures prominently increased the permeability of tight dolomite reservoirs. The initial production of the wells is four to five times the average production of other wells in the area, showing a good development effect. Meanwhile, the updated numerical simulation validates that the history match accuracy of water cut based on the dual-porosity model is significantly improved, proving the fracture evaluation and prediction results to be relatively reliable and applicable.展开更多
基金conducted with funding provided by the California Energy Commission under the contract PIR-16-027 for Research on Risk Management Framework for Underground Natural Gas infrastructure in California。
文摘In this study,we numerically investigate the influence of hysteretic stress path behavior on the seal integrity during underground gas storage operations in a depleted reservoir.Our study area is the Honor Rancho Underground Storage Facility in Los Angeles County(California,USA),which was converted into an underground gas storage facility in 1975 after 20 years of oil and gas production.In our simulations,the geomechanical behavior of the sand reservoir is modeled using two models:(1)a linear elastic model(non-hysteretic stress path)that does not take into consideration irreversible deformation,and(2)a plastic cap mechanical model which considers changes in rock elastic properties due to irreversible deformations caused by plastic reservoir compaction(hysteretic stress path).It shows that the irreversible compaction of the geological layer over geologic time and during the reservoir depletion can have important consequences on stress tensor orientation and magnitude.Ignoring depletion-induced irreversible compaction can lead to an over-estimation of the calculation of the maximum working reservoir pressure.Moreover,this irreversible compaction may bring the nearby faults closer to reactivation.However,regardless of the two models applied,the geomechanical analysis shows that for the estimated stress conditions applied in this study,the Honor Rancho Underground Storage Facility is being safely operated at pressures much below what would be required to compromise the seal integrity.
基金funded by the Assistant Secretary for Fossil Energy,National Energy Technology Laboratory,National Risk Assessment Partnership of the U.S.Department of Energy under Contract No.DEAC02-05CH11231Swiss National Science Foundation Ambizione Energy grant(PZENP2_160555)
文摘Carbon capture and storage(CCS) in geologic formations has been recognized as a promising option for reducing carbon dioxide(CO) emissions from large stationary sources.However,the pressure buildup inside the storage formation can potentially induce slip along preexisting faults,which could lead to felt seismic ground motion and also provide pathways for brine/COleakage into shallow drinking water aquifers.To assess the geomechanical stability of faults,it is of crucial importance to know the in situ state of stress.In situ stress measurements can provide some information on the stresses acting on faults but with considerable uncertainties.In this paper,we investigate how such uncertainties,as defined by the variation of stress measurements obtained within the study area,could influence the assessment of the geomechanical stability of faults and the characteristics of potential injection-induced seismic events.Our modeling study is based on a hypothetical industrial-scale carbon sequestration project assumed to be located in the Southern San Joaquin Basin in California,USA.We assess the stability on the major(25 km long) fault that bounds the sequestration site and is subjected to significant reservoir pressure changes as a result of 50 years of COinjection.We present a series of geomechanical simulations in which the resolved stresses on the fault were varied over ranges of values corresponding to various stress measurements performed around the study area.The simulation results are analyzed by a statistical approach.Our main results are that the variations in resolved stresses as defined by the range of stress measurements had a negligible effect on the prediction of the seismic risk(maximum magnitude),but an important effect on the timing,the seismicity rate(number of seismic events) and the location of seismic activity.
基金supported by the National Science and Technology Major Project“Reservoir Characterization of Typical Thick Carbonate Reservoirs in the Middle East”(Grant No.2017ZX05032004-001).
文摘The Asmari Formation in the G oilfield on the Iran-Iraq border is a fractured-porous multi-lithology mixed reservoir, for which fracture is an important factor affecting oil productivity and water cut. The characterization and modeling of fractures in the carbonate reservoir of G oilfield are challenging due to weak conventional well log responses of fractures and a lack of specific logs, such as image logs. This study proposes an integrated approach for characterizing and modeling fractures in the carbonate reservoir. The features, formation mechanism, influencing factors, and prediction methods of fractures in the Asmari Formation carbonate reservoirs of G oilfield were studied using core observation, thin section, image log, cross-dipole acoustic log (CDAL), geomechanics numerical simulation (GNS), and production data. According to CDAL-based fracture density interpretation, GNS-based fracture intensity prediction between wells, and DFN-based rock fracture properties modeling, the quantitative fracture characterization for G oilfield was realized. This research shows that the fractures in the Asamri Formation are mainly medium-to high-angle shear fractures. The substantial compression stress during the Miocene played a major role in the formation of the prominent fractures and determined their trend in the region, with primary trends of NNW-SSE and NNE-SSW. The fracture distribution has regularity, and the fractures in zone A dolomites are more highly developed than that in zone B limestones vertically. Horizontally, fractures intensity is mainly controlled by faults and structural location. The results of this study may benefit the optimization of well design during field development. From 2019 to 2021, three horizontal wells pilot tests were deployed in the fractures belt in zone A, and these fractures prominently increased the permeability of tight dolomite reservoirs. The initial production of the wells is four to five times the average production of other wells in the area, showing a good development effect. Meanwhile, the updated numerical simulation validates that the history match accuracy of water cut based on the dual-porosity model is significantly improved, proving the fracture evaluation and prediction results to be relatively reliable and applicable.
