With the advancement of drilling and fracturing technology in recent years, multi-stage fractured horizontal wells have become a norm in the development of unconventional oil and gas reservoirs in North America. This has created a renewed interest in major formations of the Western Canadian Sedimentary Basin. Due to higher completion cost, it is crucial to find an optimal fracture size and spacing as well as wellbore spacing for these horizontal wells. Acid Fracturing is a stimulation process in which acid is used to enhance the conductivity of a hydraulic fracture through differential etching of the fracture face. The effectiveness of acid fracturing depends on retaining fracture conductivity under closure stress after treatment. Fracture face roughness created by the acid etching and mechanical properties of rock after acid treatment are two important factors that play a vital role in retaining conductivity after fracture closure. Acid fracturing treatments of carbonate reservoirs have yielded an increase in production in many areas of the world. The Swan Hills Formation (a member of Beaverhill Lake group) in Alberta, Canada, a carbonate oil play, is the focus of this paper.

A dual porosity model was employed to integrate core, rock mechanics, PVT, stimulation, and production data. Acid treatment data was used to estimate the fracture geometry and conductivity which was then incorporated into a three dimensional reservoir simulation model. A multi-layer, single-wellbore reservoir model of horizontal heterogeneities across the study area was built based on core calibrated formation and geomechanical log data. The model input parameters were further fine-tuned using production history matching.

The calibrated reservoir parameters, based on a history matched model, were used for initial fluid in-place estimation, production forecasting and to investigate the fracture and wellbore interference. Interference analysis was performed based on reservoir pressure depletion and decline in cumulative production. A sensitivity study of fracture density, wellbore spacing, and lateral length of wellbore was carried out and their effects on oil and gas production are discussed. Recommendations on optimal fracture and wellbore spacing for the Swan Hills Formation are also provided.

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