A recent series of tight gas discoveries in the Amin Formation of the greater Fahud area represents some of the most exciting exploration success of this decade in the Sultanate of Oman. Since discovery the two primary challenges have always been difficult breakdown and limited fracture propagation during stimulation. The early experience in the exploration and appraisal campaigns from 2009 to 2014 has led to fracture designs with conservative proppant amounts that could limit the full potential of the field. Several geomechanical studies have been commissioned in the past to guide completion strategies in well placement, perforation and fracture stimulation design. The current study focuses on hydraulic fracture breakdown and propagation pressure computations. The model employed includes initiation and propagation of a plane-strain fracture from a vertical borehole and fully coupled with viscous fluid flow. It honors key aspects of physics such as size effects of the wellbore, fracturing fluid viscosity, injection rates and injection system compressibility. The model will be introduced in the paper. Actual field experience validates results of the model. Current best practices include formation breakdown and hydraulic fracture propagation with low viscosity fluids, followed by proppant placement with high viscosity fluids. This so-called hybrid type of frac schedule has a different purpose from the widely used hybrid fracs in North America for theorized increases in fracture complexity. When applied to tight gas formations in the Sultanate of Oman, hybrid fracturing evolves from conventional designs for the purpose of successful fracture initiation, while still placing a successful job. Difficulties and similarities between North America and the Sultanate of Oman experience with hybrid type frac jobs are discussed. An overview of fracture placements showing gradual evolution from impossible-to-place to fully successful treatments is presented in the paper along with a theoretical justification from the model.
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