Optimization workflow for stimulation-well spacing design in a multiwell pad

Abstract

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. Key words: horizontal well, multi-staged fracturing, fracture flow capacity, fracture length, well space, fracture space, parameters optimization