Paleostress plays a significant role in controlling the formation, accumulation, and distribution of reservoirs, and this could be an important factor in controlling the production of hydrocarbons from the unconventio...Paleostress plays a significant role in controlling the formation, accumulation, and distribution of reservoirs, and this could be an important factor in controlling the production of hydrocarbons from the unconventional reservoirs. In this study, we will use 3D seismic reflection data to perform the slip-tendency-based stress inversion to determine the stress field in the basement of the northern slope area in the Bongor Basin. The dataset for this technique is easily available in the oil and gas companies. The stress inversion results from the basement of the northern slope area of Bongor basin show that the maximum principal stress axis (σ1) is oriented vertically, the intermediate principal stress axis (σ2) is oriented N18° and the minimum principal stress axis (σ3) is oriented N105°, and σ2/σ1 = 0.60 and σ3/σ1 = 0.29. The findings of this paper provide significant information to understand the fault reactivation at the critical stage of hydrocarbon accumulation and the regional tectonic evolution.展开更多
The Youngstown earthquake sequence of 2011 is one of the clearest examples of inadvertently induced seismicity for which detailed documentation is available.In this paper,we investigate(i) likely stress states in the ...The Youngstown earthquake sequence of 2011 is one of the clearest examples of inadvertently induced seismicity for which detailed documentation is available.In this paper,we investigate(i) likely stress states in the vicinity of the injection well,(ii) a range of likely permeability scenarios,and(iii) relatively simple methods by which induced seismicity can be evaluated and mitigated.We use relocated hypocenters from the seismic sequence to construct a basement fault structure,which is then used to serve as a reference surface within the basement,and on which we calculate the effects of pore pressure changes induced by the injection activities of the Northstar #1 injection well.We also deduce an in situ(preinjection) strike-slip stress regime,where ρ2≈ρ3,and it is consistent with both recent earthquake data and published stress estimates for the region.If the reactivation characteristics of the basement are known or assumed,a critical or threshold slip tendency can be determined and the basement faults can be analyzed for the likelihood of reactivation in a perturbed pore pressure field.Comparison of well injection pressures and simulated pore pressure perturbations within the basement below the injection well indicates that permeability anisotropy is necessary to generate sufficient pore pressure perturbation to induce fault reactivation.Simulations of the well’s injection history show that our estimate of in situ stress state,coupled with a highly anisotropic permeability structure,can generate sufficient pore pressure perturbation on the inferred basement structure to cause reactivation,potentially slipping an area of approximately 4×10~5 m~2.展开更多
Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries.The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and ha...Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries.The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and has been deformed under the ENE–WSW maximum horizontal compression since the late Pliocene.In this study,we analyzed short-term instrumental seismic(focal mechanism)and long-term paleoseis-mic(Quaternary fault outcrop)data to decipher the neotectonic crustal deformation pattern in the south-eastern Korean Peninsula.Available(paleo-)seismic data acquired from an NNE–SSW trending deformation zone between the Yangsan and Ulleung fault zones indicate spatial partitioning of crustal deformation by NNW–SSE to NNE–SSW striking reverse faults and NNE–SSW striking strike-slip faults,supporting a strike-slip partitioned transpression model.The instantaneous and finite neotectonic strains,estimated from the focal mechanism and Quaternary outcrop data,respectively,show discrepan-cies in their axes,which can be attributed to the switching between extensional and intermediate axes of finite strain during the accumulation of wrench-dominated transpression.Notably,some major faults,including the Yangsan and Ulsan fault zones,are relatively misoriented to slip under the current stress condition but,paradoxically,have more(paleo-)seismic records indicating their role in accommodating the neotectonic transpressional strain.We propose that fluids,heat flow,and lithospheric structure are potential factors affecting the reactivation of the relatively misoriented major faults.Our findings provide insights into the accommodation pattern of strain associated with the neotectonic crustal extrusion in an intraplate region of the eastern Eurasian Plate in response to the collision of the Indian Plate and the sub-duction of the Pacific/Philippine Sea Plates.展开更多
文摘Paleostress plays a significant role in controlling the formation, accumulation, and distribution of reservoirs, and this could be an important factor in controlling the production of hydrocarbons from the unconventional reservoirs. In this study, we will use 3D seismic reflection data to perform the slip-tendency-based stress inversion to determine the stress field in the basement of the northern slope area in the Bongor Basin. The dataset for this technique is easily available in the oil and gas companies. The stress inversion results from the basement of the northern slope area of Bongor basin show that the maximum principal stress axis (σ1) is oriented vertically, the intermediate principal stress axis (σ2) is oriented N18° and the minimum principal stress axis (σ3) is oriented N105°, and σ2/σ1 = 0.60 and σ3/σ1 = 0.29. The findings of this paper provide significant information to understand the fault reactivation at the critical stage of hydrocarbon accumulation and the regional tectonic evolution.
基金supported in part by Southwest Research Institute Internal Research and Development Projects R8456 and R8654provided by NSF grant EAR-0847688USGS NEHRP grant 2016-0172
文摘The Youngstown earthquake sequence of 2011 is one of the clearest examples of inadvertently induced seismicity for which detailed documentation is available.In this paper,we investigate(i) likely stress states in the vicinity of the injection well,(ii) a range of likely permeability scenarios,and(iii) relatively simple methods by which induced seismicity can be evaluated and mitigated.We use relocated hypocenters from the seismic sequence to construct a basement fault structure,which is then used to serve as a reference surface within the basement,and on which we calculate the effects of pore pressure changes induced by the injection activities of the Northstar #1 injection well.We also deduce an in situ(preinjection) strike-slip stress regime,where ρ2≈ρ3,and it is consistent with both recent earthquake data and published stress estimates for the region.If the reactivation characteristics of the basement are known or assumed,a critical or threshold slip tendency can be determined and the basement faults can be analyzed for the likelihood of reactivation in a perturbed pore pressure field.Comparison of well injection pressures and simulated pore pressure perturbations within the basement below the injection well indicates that permeability anisotropy is necessary to generate sufficient pore pressure perturbation to induce fault reactivation.Simulations of the well’s injection history show that our estimate of in situ stress state,coupled with a highly anisotropic permeability structure,can generate sufficient pore pressure perturbation on the inferred basement structure to cause reactivation,potentially slipping an area of approximately 4×10~5 m~2.
基金This research was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant(no.20212010200020)the Energy&Mineral Resources Develop-ment Association of Korea(EMRD)grant(Datascience based oil/gas exploration consortium),funded by the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea.
文摘Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries.The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and has been deformed under the ENE–WSW maximum horizontal compression since the late Pliocene.In this study,we analyzed short-term instrumental seismic(focal mechanism)and long-term paleoseis-mic(Quaternary fault outcrop)data to decipher the neotectonic crustal deformation pattern in the south-eastern Korean Peninsula.Available(paleo-)seismic data acquired from an NNE–SSW trending deformation zone between the Yangsan and Ulleung fault zones indicate spatial partitioning of crustal deformation by NNW–SSE to NNE–SSW striking reverse faults and NNE–SSW striking strike-slip faults,supporting a strike-slip partitioned transpression model.The instantaneous and finite neotectonic strains,estimated from the focal mechanism and Quaternary outcrop data,respectively,show discrepan-cies in their axes,which can be attributed to the switching between extensional and intermediate axes of finite strain during the accumulation of wrench-dominated transpression.Notably,some major faults,including the Yangsan and Ulsan fault zones,are relatively misoriented to slip under the current stress condition but,paradoxically,have more(paleo-)seismic records indicating their role in accommodating the neotectonic transpressional strain.We propose that fluids,heat flow,and lithospheric structure are potential factors affecting the reactivation of the relatively misoriented major faults.Our findings provide insights into the accommodation pattern of strain associated with the neotectonic crustal extrusion in an intraplate region of the eastern Eurasian Plate in response to the collision of the Indian Plate and the sub-duction of the Pacific/Philippine Sea Plates.
