On 2019-03-04,the largest induced earthquake(ML4.18)occurred in the East Shale Basin,Alberta,and the underlying physical mechanisms have not been fully understood.This paper proposes a synthetical geoengineering metho...On 2019-03-04,the largest induced earthquake(ML4.18)occurred in the East Shale Basin,Alberta,and the underlying physical mechanisms have not been fully understood.This paper proposes a synthetical geoengineering methodology to comprehensively characterize this earthquake caused by hydraulic fracturing.Based on 3D structural,petrophysical,and geomechanical models,an unconventional fracture model is constructed by considering the stress shadow between adjacent hydraulic fractures and the interactions between hydraulic and natural fractures.Coupled poroelastic simulations are conducted to reveal the triggering mechanisms of induced seismicity.It is found that four vertical basement-rooted faults were identified via focal mechanisms analysis.The brittleness index(BI)along two horizontal wells has a high magnitude(BI>0.5),indicating the potential susceptibility of rock brittleness.Due to the presence of overpressure,pre-existing faults in the Duvernay Formation are highly susceptible to fault reactivation.The occurrence of the earthquake clusters has been attributed to the fracturing fluid injection during the west 38^(th)-39^(th) stage and east 38^(th) stage completions.Rock brittleness,formation overpressure,and large fracturing job size account for the nucleation of earthquake clusters,and unconventional natural-hydraulic fracture networks provide fluid flow pathways to cause fault reactivation.This workflow can be used to mitigate potential seismic risks in unconventional reservoirs in other fields.展开更多
Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complet...Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complete harvesting ban measures in recent decades,the forest tree species and age cohorts have become relatively homogenous,and the biodiversity and ecological functions have been reduced.To design effective forest management options to optimize forest structure and increase carbon sequestration capacity,Mao County in Sichuan Province was selected as the study site and six forest management options(harvesting,planting)of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate(ACSR)between these options and the current management option over the next 100 years.Our results showed that(i)the different harvesting and planting intensities significantly changed the ACSR compared with the current management options;(ii)different communities responded differently to the management options,with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees(P<0.05);and(iii)a comprehensive consideration of forest management options at the species,community and landscape levels was necessary.Our results suggest that implementing a longer harvesting and planting interval(20 years)at the study site can maximize forest ACSR.This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.展开更多
基金This research was supported by Science Foundation of China University of Petroleum,Beijing(No.2462023BJRC001)National Natural Science Foundation of China Project(No.52204039).
文摘On 2019-03-04,the largest induced earthquake(ML4.18)occurred in the East Shale Basin,Alberta,and the underlying physical mechanisms have not been fully understood.This paper proposes a synthetical geoengineering methodology to comprehensively characterize this earthquake caused by hydraulic fracturing.Based on 3D structural,petrophysical,and geomechanical models,an unconventional fracture model is constructed by considering the stress shadow between adjacent hydraulic fractures and the interactions between hydraulic and natural fractures.Coupled poroelastic simulations are conducted to reveal the triggering mechanisms of induced seismicity.It is found that four vertical basement-rooted faults were identified via focal mechanisms analysis.The brittleness index(BI)along two horizontal wells has a high magnitude(BI>0.5),indicating the potential susceptibility of rock brittleness.Due to the presence of overpressure,pre-existing faults in the Duvernay Formation are highly susceptible to fault reactivation.The occurrence of the earthquake clusters has been attributed to the fracturing fluid injection during the west 38^(th)-39^(th) stage and east 38^(th) stage completions.Rock brittleness,formation overpressure,and large fracturing job size account for the nucleation of earthquake clusters,and unconventional natural-hydraulic fracture networks provide fluid flow pathways to cause fault reactivation.This workflow can be used to mitigate potential seismic risks in unconventional reservoirs in other fields.
基金funded by the National Natural Science Foundation of China(41801185,32171550)the Natural Science Foundation of Sichuan Province(2023NSFSC0191)+1 种基金the Strategic Priority Research Program(category A)of Chinese Academy of Sciences(XDA20020302)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2021371).
文摘Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complete harvesting ban measures in recent decades,the forest tree species and age cohorts have become relatively homogenous,and the biodiversity and ecological functions have been reduced.To design effective forest management options to optimize forest structure and increase carbon sequestration capacity,Mao County in Sichuan Province was selected as the study site and six forest management options(harvesting,planting)of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate(ACSR)between these options and the current management option over the next 100 years.Our results showed that(i)the different harvesting and planting intensities significantly changed the ACSR compared with the current management options;(ii)different communities responded differently to the management options,with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees(P<0.05);and(iii)a comprehensive consideration of forest management options at the species,community and landscape levels was necessary.Our results suggest that implementing a longer harvesting and planting interval(20 years)at the study site can maximize forest ACSR.This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.
