Stress shadow size and aperture of hydraulic fractures in unconventional shales

• Key parameters in optimization of distance between hydraulic fractures are introduced.
• Different stress shadow mechanisms are discussed and their characteristics are presented.
• Simultaneous and standalone fracing are investigated for contained and uncontained fractures.
• Effect of considering different threshold angles in stress shadow calculation is studied.
• A comprehensive set of equations is proposed for stress shadow and aperture of hydraulic fractures.

Multistage hydraulic fracturing completions together with simultaneous fracturing of parallel laterals are central to enhance productivity of horizontal wells completed in shale reservoirs with extremely low permeability. An efficient fracture network in the reservoir with the least number of deviated or collapsed fractures prevents poor connectivity with the surrounding reservoir volume, reduction in reserve estimates per well, loss in well productivity, reduced drainage areas, and higher completion costs associated with the ineffective fractures. Ignoring the local stress redistribution due to the stress shadow effect may cause fracture deviation or collapse. In this work, a comprehensive numerical study of stress shadow and aperture of three-dimensional hydraulic fractures is presented. Four different scenarios consisting of single or simultaneous hydraulic fractures, contained or not contained, are studied. Key influencing parameters are introduced, different shadow mechanisms are discussed, and a comprehensive set of equations is proposed for stress shadow and aperture prediction of hydraulic fractures. The work presented herein is likely to offer several practical benefits: firstly, it enables improved planning and placement of productive hydraulic fracture treatments; secondly, it offers the potential for considerable cost reductions in completion design and implementation; and thirdly, it allows for an optimal multistage hydraulic fracture treatment that drains larger volumes of the reservoir.