It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes t...It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes to use packers,sealing cannula and other tools in the same horizontal well to inject water in some fractures and produce oil from other fractures.This new energy supplement method forms a segmental synchronous injection-production system in a horizontal well.The method can reduce the distance between the injection end and the production end,and quickly establish an effective displacement system.Changing the displacement between wells to displacement between horizontal well sections,and point water flooding to linear uniform water flooding,the method can enhance water sweeping volume and shorten waterflooding response period.The research shows that:(1)In the synchronous injection and production of horizontal well in an ultra-low-permeability sandstone reservoir,the water injection section should select the section where the natural fractures and artificial fractures are in the same direction or the section with no natural fractures,and the space between two sections should be 60?80 m.(2)In addition to controlling injection pressure,periodic water injection can be taken to reduce the risk of re-opening and growth of natural fractures or formation fracture caused by the gradual increase of water injection pressure with water injection going on.(3)Field tests have verified that this method can effectively improve the output of single well and achieve good economic benefits,so it can be widely used in the development of ultra-low permeability sandstone reservoirs.展开更多
基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值...基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值的电流/电压超调。为了解决超调问题,保证电池充电稳定性,提出了一种抗饱和控制策略。首先,基于WPT系统的等效电路模型分析最大效率点跟踪的工作原理;然后,结合WPT系统两侧控制量的协同工作过程,解析系统启动及电池恒流恒压充电切换时的超调现象,给出恒流恒压控制器设计方法,将反计算抗饱和算法与控制器设计相结合,提出抗饱和控制策略;最后,搭建了仿真模型,验证所提出的抗饱和策略能够有效抑制控制器饱和导致的超调,减少系统到达稳态的时间,降低电流/电压的超调带来的元器件应力。展开更多
A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress ...A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.展开更多
基金Supported by the China National Science and Technology Major Project(2016ZX05050)
文摘It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes to use packers,sealing cannula and other tools in the same horizontal well to inject water in some fractures and produce oil from other fractures.This new energy supplement method forms a segmental synchronous injection-production system in a horizontal well.The method can reduce the distance between the injection end and the production end,and quickly establish an effective displacement system.Changing the displacement between wells to displacement between horizontal well sections,and point water flooding to linear uniform water flooding,the method can enhance water sweeping volume and shorten waterflooding response period.The research shows that:(1)In the synchronous injection and production of horizontal well in an ultra-low-permeability sandstone reservoir,the water injection section should select the section where the natural fractures and artificial fractures are in the same direction or the section with no natural fractures,and the space between two sections should be 60?80 m.(2)In addition to controlling injection pressure,periodic water injection can be taken to reduce the risk of re-opening and growth of natural fractures or formation fracture caused by the gradual increase of water injection pressure with water injection going on.(3)Field tests have verified that this method can effectively improve the output of single well and achieve good economic benefits,so it can be widely used in the development of ultra-low permeability sandstone reservoirs.
文摘基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值的电流/电压超调。为了解决超调问题,保证电池充电稳定性,提出了一种抗饱和控制策略。首先,基于WPT系统的等效电路模型分析最大效率点跟踪的工作原理;然后,结合WPT系统两侧控制量的协同工作过程,解析系统启动及电池恒流恒压充电切换时的超调现象,给出恒流恒压控制器设计方法,将反计算抗饱和算法与控制器设计相结合,提出抗饱和控制策略;最后,搭建了仿真模型,验证所提出的抗饱和策略能够有效抑制控制器饱和导致的超调,减少系统到达稳态的时间,降低电流/电压的超调带来的元器件应力。
基金Supported by the Joint Fund Project of the National Natural Science Foundation of China(U22B2075).
文摘A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.
