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Summary This paper summarizes the integrated technical learnings from success with unconventional hydraulically fractured producers in a tight silicate reservoir located in Southern Oman. It shows the results and development challenges from a project to extend the proof of concept into further field development, maturing commercial volumes, and meeting the project’s value drivers. The producing reservoir is more than 3,000 m deep, encapsulated in salt and over-pressured. It contains light, sour oil with H2S/CO2 contents of 1 and 2 mol%, respectively. Two wells were fracked with unconventional fracs as a new trail to the field. Previous wells were completed with conventional fracs. The result was used to formulate a phased development plan and define optimum subsurface decisions. Frac parameters were matched in Ghofer using actual pumping data. Dynamic Compute Modelling Group models with frac models were then used to match well test and PLT results. These models were subsequently used to generate production forecasts and defining the optimum subsurface decisions such that the project remains cost-competitive within the company’s project portfolio. The two first unconventionally fracked wells show promising results in this tight sour reservoir. Unconventional fracking created longer fractures than conventional frac mainly due to less fracture damage and proves to deliver economic and competitive oil rates. Guar-based gel creates thicker shorter fractures. High-Viscosity-Frication-Reducer (HVFR) creates thinner and longer fractures. With unconventional fracs, the number stages were increased versus conventionally fracked wells, increasing reservoir coverage by factor three compared to conventionally fracked wells, and producing five times more oil rate at higher Tubing-Head- Pressures. Optimal Unconventional frac design and well spacing and number were evaluated jointly. To further optimize frac design, along term trial plan will be implemented. The study shows that factors such as matrix permeability, frac heigh and half- length mainly impact recovery. The project went through multiple project milestones to evaluate and optimize the development and select optimum project decisions that best meet the project’s value drivers. The team optimized well number, placement & frac design, material, and completion. This paper discusses the unconventional frac result in a sour reservoir with all related challenges and project decisions. The authors have summarized the results from the successful unconventional frac, and field development decision related to the subsurface, frac and well designs that should be taken in an integration way. The study outcomes can be learnt from and replicated in similar sour tight reservoir fields.
Harrasi et al. (Mon,) studied this question.