In the design of a shale-gas cluster horizontal well,it is necessary to consider the bypass of the fracturing influence domains of existing wells and the interference between fracturing influence domains when the well...In the design of a shale-gas cluster horizontal well,it is necessary to consider the bypass of the fracturing influence domains of existing wells and the interference between fracturing influence domains when the wellbore trajectories of infill adjustment wells in the fracturing areas are designed.In order to quickly evaluate the rationality of the design scheme of fracturing wellbore trajectory in an infill adjustment well,this paper adopted the vector algebra method to build a geometric model of the obstacles in the shale gas fracturing area.In this geometric model,the influence domains of hydraulic fractures are taken into account.Then,based on this geometric model,the optimization design model of bypass trajectory in the shale gas fracturing area was established by taking the minimization of total trajectory length and trajectory potential energy as the optimization objective and the anti-collision between trajectories as the constraint.Besides,the geometric check method to judge if there is any interference between fracturing influence domains was provided.Finally,the established optimization design model was verified based on the actual drilling data of Fuling Shale Gas Field in the Sichuan Basin.And the following research results were obtained.First,the obstacle sizes in fracturing areas will be seriously underestimated if the fracturing influence domains are neglected.Second,if the fracturing influence domains are neglected,the designed bypass trajectory can bypass the wellbore trajectories of old wells,but may intersect the fracturing influence domains of existing wells,thus inducing drilling accidents.In conclusion,the proposed optimization design model of bypass trajectory in the shale gas fracturing area can satisfy the constraint of anti-collision and bypass and achieve the optimization objective of minimizing total trajectory length and trajectory potential energy,and the corresponding design calculation avoids complex calculation and check.展开更多
To evaluate the fracturing effect and dynamic change process after volume fracturing with vertical wells in low permeability oil reservoirs, an oil-water two-phase flow model and a well model are built. On this basis,...To evaluate the fracturing effect and dynamic change process after volume fracturing with vertical wells in low permeability oil reservoirs, an oil-water two-phase flow model and a well model are built. On this basis, an evaluation method of fracturing effect based on production data and fracturing fluid backflow data is established, and the method is used to analyze some field cases. The vicinity area of main fracture after fracturing is divided into different stimulated regions. The permeability and area of different regions are used to characterize the stimulation strength and scale of the fracture network. The conductivity of stimulated region is defined as the product of the permeability and area of the stimulated region. Through parameter sensitivity analysis, it is found that half-length of the fracture and the permeability of the core area mainly affect the flow law near the well, that is, the early stage of production;while matrix permeability mainly affects the flow law at the far end of the fracture. Taking a typical old well in Changqing Oilfield as an example, the fracturing effect and its changes after two rounds of volume fracturing in this well are evaluated. It is found that with the increase of production time after the first volume fracturing, the permeability and conductivity of stimulated area gradually decreased, and the fracturing effect gradually decreased until disappeared;after the second volume fracturing, the permeability and conductivity of stimulated area increased significantly again.展开更多
文摘In the design of a shale-gas cluster horizontal well,it is necessary to consider the bypass of the fracturing influence domains of existing wells and the interference between fracturing influence domains when the wellbore trajectories of infill adjustment wells in the fracturing areas are designed.In order to quickly evaluate the rationality of the design scheme of fracturing wellbore trajectory in an infill adjustment well,this paper adopted the vector algebra method to build a geometric model of the obstacles in the shale gas fracturing area.In this geometric model,the influence domains of hydraulic fractures are taken into account.Then,based on this geometric model,the optimization design model of bypass trajectory in the shale gas fracturing area was established by taking the minimization of total trajectory length and trajectory potential energy as the optimization objective and the anti-collision between trajectories as the constraint.Besides,the geometric check method to judge if there is any interference between fracturing influence domains was provided.Finally,the established optimization design model was verified based on the actual drilling data of Fuling Shale Gas Field in the Sichuan Basin.And the following research results were obtained.First,the obstacle sizes in fracturing areas will be seriously underestimated if the fracturing influence domains are neglected.Second,if the fracturing influence domains are neglected,the designed bypass trajectory can bypass the wellbore trajectories of old wells,but may intersect the fracturing influence domains of existing wells,thus inducing drilling accidents.In conclusion,the proposed optimization design model of bypass trajectory in the shale gas fracturing area can satisfy the constraint of anti-collision and bypass and achieve the optimization objective of minimizing total trajectory length and trajectory potential energy,and the corresponding design calculation avoids complex calculation and check.
基金Supported by the China National Science and Technology Major Project (2017ZX05013-001)CNPC Science and Technology Major Research Project (2018B-4907)
文摘To evaluate the fracturing effect and dynamic change process after volume fracturing with vertical wells in low permeability oil reservoirs, an oil-water two-phase flow model and a well model are built. On this basis, an evaluation method of fracturing effect based on production data and fracturing fluid backflow data is established, and the method is used to analyze some field cases. The vicinity area of main fracture after fracturing is divided into different stimulated regions. The permeability and area of different regions are used to characterize the stimulation strength and scale of the fracture network. The conductivity of stimulated region is defined as the product of the permeability and area of the stimulated region. Through parameter sensitivity analysis, it is found that half-length of the fracture and the permeability of the core area mainly affect the flow law near the well, that is, the early stage of production;while matrix permeability mainly affects the flow law at the far end of the fracture. Taking a typical old well in Changqing Oilfield as an example, the fracturing effect and its changes after two rounds of volume fracturing in this well are evaluated. It is found that with the increase of production time after the first volume fracturing, the permeability and conductivity of stimulated area gradually decreased, and the fracturing effect gradually decreased until disappeared;after the second volume fracturing, the permeability and conductivity of stimulated area increased significantly again.
