An approach for the performance-impact of parent-child wellbores spacing and hydraulic fractures cluster spacing in conventional and unconventional reservoirs

Abstract

The objective of this paper is focusing deep insights on the impacts of the spacing between parent and child wellbores and between hydraulic fractures on the performance of conventional and unconventional reservoirs. The target is developing a quantitative approach for determining these impacts on pressure responses, flow regimes, and productivity indices during the entire production life of these reservoirs. The motivation of this study is the willing to set-up and define clearly the criteria for the optimum spacing between wellbores and fractures that could give the maximum productivity considering different reservoir configurations and wellbore types.The methodology used in this study consists of four tasks. The first includes developing several analytical models for pressure behavior, and productivity index of reservoirs depleted by multilateral wells intersected by multiple hydraulic fractures. These models are applicable for conventional and unconventional reservoirs. The second demonstrates the solutions of these models using a state of the art computational tools and considering different spacings between these laterals and different spacings between fractures. The third concentrates on characterizing the production interference caused by the narrow spacing between fractures and short spacing between wellbores. This interference can be predicted from the changes in the flow regimes seen on pressure derivative curves. The last task focuses on proposing a quantitative measure for the optimum spacing between parent-child wellbores and optimum spacing between hydraulic fractures that could give the maximum productivity during the entire production life of the reservoirs.The observations are summarized in: 1) The impact of parent-child spacing is more influential than the impact of hydraulic fracture spacing. A significant increase in the productivity index is pointed out by increasing the number of the wellbore and decreasing the spacing between them while a very slight increase is seen in spite of the large increase in the number of hydraulic fractures. 2) The interference caused by parent-child spacing is seen after the interference of fracture spacing. The first one impacts linear flow regime when reservoir fluids flow from the drainage area beyond fracture tips to the area between hydraulic fractures while the second one impacts bilinear flow regime when reservoir fluids move toward hydraulic fractures. 3) The Frac-Hit, represented by the direct contact between hydraulic fractures of two adjacent wellbores, could cause a significant decline in the total productivity index of the production system. 4) The optimum wellbore spacing in fractured reservoirs depends on the number of hydraulic fractures propagated from these wellbores.The novel points presented in this study are: 1) New approach for estimating the optimum wellbore spacing and fracture spacing in conventional and unconventional reservoirs. 2) The possibilities for predicting the starting time of production interference caused by narrow spacings between fractures and wellbores. 3) The optimum spacing between hydraulic fractures is in the range of (10−30acres) for each fracture.