Hydraulic Fracturing Design and Optimization: A Modification to Zipper Frac

TLDR

Recent advances in hydraulic fracturing, such as zipper frac, aim to reduce stress contrast, increase stimulated reservoir volume, and simultaneously stimulate two parallel wells, yet optimal design remains debated by the industry. The paper proposes a new design to optimize fracturing of two laterals from both rock‑mechanics and fluid‑production perspectives. The modified zipper frac initiates fractures in a staggered pattern, causing them to propagate toward each other and redirect stress to propagate perpendicularly, with well spacing analytically evaluated to optimize normal‑stress changes. The modified zipper frac increases contact area and fluid production, outperforming the original design.

Abstract

Abstract In recent years, new fracturing designs and techniques have been developed to enhance production of trapped hydrocarbons. The new techniques focus on reducing stress contrast during fracture propagation while enhancing far field complexity and maximizing the stimulated reservoir volume. Zipper frac is one of these techniques, which involves simultaneous stimulation of two parallel horizontal wells from toe to heel. In this technique, created fractures in each cluster propagate toward each other so that the induced stresses near the tips force fracture propagation to a direction perpendicular to the main fracture. The effectiveness of zipper frac has been approved by the industry; however, the treatment's optimization is still under discussion. In this paper, we present a new design to optimize fracturing of two laterals from both rock mechanic and fluid production aspects. The new design is a modification to zipper frac, where fractures are initiated in a staggered pattern. The effect of well spacing on the changes in normal stress has been evaluated analytically to optimize the design. Results demonstrate that the modified zipper frac improves the performance of fracturing treatment when compared to the original zipper frac by means of increasing contact area and eventually enhancing fluid production.