This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reser...This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reservoir conditions after shale hydration.Stress-strain data and mechanical parameters of shale after hydration under high temperature and high pressure were obtained to investigate the effects of reservoir temperature,hydration time and horizontal stress difference on the mechanical strength of shale after hydration.By using nonlinear regression and interpolation methods,a prediction model for the mechanical strength of shale after hydration was constructed,and the mechanical strength chart of deep shale under high stress difference was plotted.First,higher hydration temperature,longer hydration reaction time,and greater horizontal stress difference cause shale to enter the yield stage earlier during the compression process after hydration and to exhibit more prominent plastic characteristics,lower peak strength,peak strain,residual strength and elastic modulus,and higher Poisson's ratio.Second,the longer the hydration time,the smaller the impact of hydration temperature on the mechanical strength of deep shale is.As the horizontal stress difference increases,the peak strength and residual strength weaken intensely,and the peak strain,elastic modulus and Poisson's ratio deteriorate slowly.Third,the mechanical strength of shale decreases significantly in the first 5 days of hydration,but gradually stabilizes as the hydration time increases.Fourth,the visual mechanical strength chart helps to understand the post-fracturing dynamics in deep shale gas reservoir fracturing site and adjust the drainage and production plan in time.展开更多
基金Supported by the National Natural Science Foundation of China(U24A2084,U21B2071)Science and Technology Cooperation Project of CNPC-Southwest Petroleum University Innovation Consortium(2020CX030201)。
文摘This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reservoir conditions after shale hydration.Stress-strain data and mechanical parameters of shale after hydration under high temperature and high pressure were obtained to investigate the effects of reservoir temperature,hydration time and horizontal stress difference on the mechanical strength of shale after hydration.By using nonlinear regression and interpolation methods,a prediction model for the mechanical strength of shale after hydration was constructed,and the mechanical strength chart of deep shale under high stress difference was plotted.First,higher hydration temperature,longer hydration reaction time,and greater horizontal stress difference cause shale to enter the yield stage earlier during the compression process after hydration and to exhibit more prominent plastic characteristics,lower peak strength,peak strain,residual strength and elastic modulus,and higher Poisson's ratio.Second,the longer the hydration time,the smaller the impact of hydration temperature on the mechanical strength of deep shale is.As the horizontal stress difference increases,the peak strength and residual strength weaken intensely,and the peak strain,elastic modulus and Poisson's ratio deteriorate slowly.Third,the mechanical strength of shale decreases significantly in the first 5 days of hydration,but gradually stabilizes as the hydration time increases.Fourth,the visual mechanical strength chart helps to understand the post-fracturing dynamics in deep shale gas reservoir fracturing site and adjust the drainage and production plan in time.
文摘研究伴自杀意念(suicidal ideation,SI)的抑郁症患者、不伴自杀意念(no suicidal ideation,NSI)的抑郁症患者、健康对照(healthy controls,HC)的静息态功能性核磁共振(resting-state functional magnetic resonance imaging,rs-fMRI)低频振幅(amplitude of low frequency fluctuations,ALFF)的活动差异,通过对患者rs-fMRI的脑功能进行Meta分析。在Pubmed、Embase、Web of Science、Cochrane Library、中国知网、万方数据库中搜索关于伴SI的抑郁患者rs-fMRI的相关文献。依据系统评价的方法,对纳入文献进行筛选、质量评价、提取特征、激活似然估计法(activation likelihood estimation,ALE)Meta分析,汇总了既往文献的SI抑郁症患者、NSI抑郁症患者与HC之间的ALFF的收敛脑区。共纳入6篇文献,提取SI组患者175例,NSI组患者137例,HC组125名,其中SI组和NSI组之间的差异脑区共有18个。将差异脑区纳入ALE Meta分析,结果显示:SI组相较于NSI组ALFF增高的脑区有左侧枕叶舌回(ALE=1.859×10^(-2),P<0.01,Z=5.688)、右侧枕中回(ALE=1.823×10^(-2),P<0.01,Z=5.562)。左侧枕叶舌回及右侧枕中回异常激活与抑郁症患者的自杀意念可能相关。
