High permeability hydraulic fracturing in Nimr cluster of oil fields within the Sultanate of Oman has been gaining momentum in recent years. This is despite of the inherent resistance towards deferring producing wells for a typically long intervention such as hydraulic fracturing. In part, that is due to the required pre fracturing preparation which ranges from removing low grade existing completion, removal of artificial lift pumps, installing fracturing completion, and finally post fracturing recompletion. This is in addition to damage presented by less-than-optimal fracturing fluids which may impair well productivity, especially in cases where oil is of moderate to high viscosity.
Hence hydraulic fracturing of high permeability formations within Nimr fields dictated an optimal candidate selection process. This paper presents well-defined candidate selection criteria derived from regression modelling, in addition to design related optimizations such as the utilization of reduced gel loading designs and enhancing oxidizing breaker concentration for better cleanup and flowback.
As part of the study within this paper, fracturing water injectors presented a less risky endeavor due to a shorter turnaround time from pre to post fracturing. It also presented an opportunity to enhance sweep efficiency in fields where water injectors are underperforming.
Injector wells within the Nimr cluster of fields generally target high permeability formations (10-200 mD), however due to the quality of injected water and the degree of self-scaling due to temperature and pressure changes, skin build up is common. Hence the introduction of fracturing presented an efficient technique to bypass damage and generate larger conductive effective wellbore radii.
This paper describes the restoration of several poorly performing producer and injectors that were treated between 2021 and 2022 using hydraulic fracturing. Injection results as well as post fracturing sweep efficiencies were compared to those prior to fracturing. These wells were also assessed in perspective of their injection patterns where results have shown substantial pressure support to nearby wells without fast-tracking water breakthrough. This resulted in the revival of some producer wells that were previously closed in due to poor aquifer pressure support.