Fully Coupled Finite-Element–Based Numerical Model for Investigation of Interaction between an Induced and a Preexisting Fracture in Naturally Fractured Poroelastic Reservoirs: Fracture Diversion, Arrest, and Breakout

Abstract

This paper investigates the effect of a preexisting natural fracture on hydraulic fracture propagation. A fully coupled numerical poroelastic model, which includes the wellbore, the formation, a hydraulic fracture, and an arbitrarily oriented natural fracture, has been developed and used for this purpose. The possibility of fracture diversion, intersection, opening, and breakout for different angles of approach as well as natural fracture length are investigated. The fully coupled poroelastic model and the improved knowledge derived from this study have beneficial applications in the design and optimization of hydraulic fracture treatments in naturally fractured reservoirs, including tight gas, coal bed methane, and enhanced geothermal reservoirs. Results of this study have shown that the orientation of the natural fracture (penny-shaped, mineralized and/or closed natural fracture is used in this study) and fracture length can severely influence the propagation trajectory of a hydraulically induced fracture. An induced fracture is more likely to cross a natural fracture with a length equal to or less than 10 m if the angle of approach is sufficiently high; otherwise, it intersects and dilates the natural fracture (fracture arrest) and breaks out from one of the tips of the natural fracture. It is also shown that natural fracture length equal to or greater than 20 m is likely to arrest a hydraulically induced fracture.