A novel laboratory simulation method for modeling multi-staged fracturing in a horizontal well was established based on a true tri-axial hydraulic fracturing simulation system. Using this method, the influences of net...A novel laboratory simulation method for modeling multi-staged fracturing in a horizontal well was established based on a true tri-axial hydraulic fracturing simulation system. Using this method, the influences of net pressure in hydraulic fracture, stage spacing, perforation parameter, horizontal stress bias and well cementation quality on the propagation geometry of multiple fractures in a tight sandstone formation were studied in detail. The specimen splitting and analogy analysis of fracturing curve patterns reveals: Multiple fractures tend to merge under the condition of high horizontal stress bias and short stage spacing with pre-existing hydraulic fractures under critical closure situation, and the propagation of subsequent fractures is possibly suppressed because of high net pressure in pre-created fractures and asymmetric distribution of fracture width. And the subsequently created fractures are situated in the induced stress decreasing zone due to long stage spacing, leading to weak stress interference, and perforation with intense density and deep penetration facilitates the decrease of initiation fracture pressure. The deflection angle of subsequent fracture and horizontal stress variation tend to be amplified under low horizontal bias with constant net pressure in fractures. The longitudinal fracture is likely to be initiated at the interface of wellbore and concrete sample with poor cementation quality. The initiation fracture pressure of the different stages increases in turn, with the largest increase of 30%. Pressure quickly declines after initiation with low propagation pressure when the transverse hydraulic fracture is formed. The pressure reduces with fluctuation after the initiation of fracture when the fracture deflects, the extension pressure is high, and the fracture formed is tortuous and narrow. There is a violently fluctuant rise of pressure with multiple peak values when longitudinal fracture created, and it is hard to distinguish the features between the initiation stage and propagati展开更多
A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analyti...A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.展开更多
文摘A novel laboratory simulation method for modeling multi-staged fracturing in a horizontal well was established based on a true tri-axial hydraulic fracturing simulation system. Using this method, the influences of net pressure in hydraulic fracture, stage spacing, perforation parameter, horizontal stress bias and well cementation quality on the propagation geometry of multiple fractures in a tight sandstone formation were studied in detail. The specimen splitting and analogy analysis of fracturing curve patterns reveals: Multiple fractures tend to merge under the condition of high horizontal stress bias and short stage spacing with pre-existing hydraulic fractures under critical closure situation, and the propagation of subsequent fractures is possibly suppressed because of high net pressure in pre-created fractures and asymmetric distribution of fracture width. And the subsequently created fractures are situated in the induced stress decreasing zone due to long stage spacing, leading to weak stress interference, and perforation with intense density and deep penetration facilitates the decrease of initiation fracture pressure. The deflection angle of subsequent fracture and horizontal stress variation tend to be amplified under low horizontal bias with constant net pressure in fractures. The longitudinal fracture is likely to be initiated at the interface of wellbore and concrete sample with poor cementation quality. The initiation fracture pressure of the different stages increases in turn, with the largest increase of 30%. Pressure quickly declines after initiation with low propagation pressure when the transverse hydraulic fracture is formed. The pressure reduces with fluctuation after the initiation of fracture when the fracture deflects, the extension pressure is high, and the fracture formed is tortuous and narrow. There is a violently fluctuant rise of pressure with multiple peak values when longitudinal fracture created, and it is hard to distinguish the features between the initiation stage and propagati
基金Supported by the China National Science and Technology Major Project(2016ZX05037,2017ZX05063).
文摘A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.
