Assessment of critically stressed fractures due to water injection — A case study from the Devonian clastic reservoir of the Berkaoui Field, Algeria

Abstract A well-constrained geomechanical model of the Devonian clastic is presented to assess the fracture slip potential due to water injection in the Berkaoui field, Algeria. The study interval indicates a strike-slip tectonic regime with a mean maximum horizontal stress azimuth of 98°N. A total of 131 natural fractures are interpreted from acoustic image logs. These fractures have dominantly east–west strikes, with the true dips ranging between 51° and 80° toward north and south. Critically stressed fracture analysis exhibits the onset of the shear displacement of optimally oriented steeply dipping fractures occurring at 2.7 MPa of the injection-induced pressure buildup. The practical injection threshold was inferred as 7 MPa based on the caprock integrity assessment. A total of 10 out of 131 fractures (with dips ≥ 70°) can experience injection-caused slip within the maximum allowable injection limit. The east–west-oriented fractures, subparallel to the maximum horizontal stress azimuth, have a higher likelihood of being critically stressed during injection and, therefore, can contribute to permeability enhancement.