Potential production gains of multi-stage fractured wells in shale plays: sensitivity of well performance to changes in design parameters assessed with fast and accurate Gaussian solutions

Wells drilled and completed in shale acreage are guided by pre-drilling fracturing and reservoir modelling, but commonly exhibit productivity different (usually lower) from what was predicted by the simulations. Additionally, multiple wells completed in the same acreage with identical fracturing schedules will rarely result in identical well performance. Instead, a considerable spread in flow performance appears to be the norm, with some wells only having half the rate, and others twice the rate, of the average (type) well. Adopting a factory model (or cookie-cutter) approach that assumes engineering outcomes involving no uncertainty will not result in optimum field development. Gaussian Pressure-Transient (GPT) solutions (for vertical wells, horizontal wells, with and without hydraulic fractures) of the pressure diffusivity equation can be used to history-match early well-data after drilling and completion to constrain the hydraulic diffusivity of the stimulated reservoir volume and determine the achieved half-length of the hydraulic fractures. Among the principal explanations for the observed variation in well deliverability of numerous study wells are the failing of perforation clusters to produce hydraulic fractures and limited fracture half-lengths from those perforations that succeed to produce hydraulic fractures. This study analyses the sensitivity of well deliverability to variations in bottomhole pressure (controlled by the artificial lift system and choke settings), fracture half-length, fracture spacing and well spacing. Such sensitivity analyses of the impact of well-design parameters on well deliverability can be instantaneously computed (spreadsheet-based) using GPT-solutions, without the need for constructing numerical reservoir simulation models. The application of GPT-methods allows for quick learning, based on production analysis of early wells in the acreage section under development, to then subsequently guide how the productivity of any new wells − prior to their actual drilling and completion − can be improved.