Production Enhancement of Heavy Oil Reservoir at South of Sultanate of Oman Salt Basin with Implementation of Design and Data Diagnostic Cycle of Hydraulic Fracturing Campaign
Authors: Kindi O. , Al Riyami S. , Hinai S. , Al Busaidi A. , Al Mukhaini S. , Hashmi M. , Sayed M. , Konwar A. , Christiawan A. B. , Yuyan R. 
Published: October 2023

At South of the Sultanate of Oman Salt Basin province, with multiple oilfield cluster such as Asset M, Asset N, and Asset B, the production enhancement method with hydraulic fracturing stimulation technique has grown from just merely 5 treatments on trial basis till 2017 to be favorable completion and production enhancement method with over 20 fracture treatments annually in 2020 onwards.

The basin is predominantly oil reservoir came from Cambro-Ordovician and Carboniforous-Permian era layers, which consist of various sandstone reservoir such as Reservoir H family, Reservoir G family and Reservoir K. Typical characteristic of the Reservoir H within Asset M cluster is relatively shallow depth layer high permeability rock with low current reservoir pressure due to depletion lowering its lithostatic stress value, nevertheless some area in the vicinity of faults are tectonically loaded resulting to formation stress complexity that complicate the process of hydraulic propped fracturing. This fault rich region and close spacing of offset producer and injector wells are major geo-hazards that warrant controlled fracture geometry. In addition, the reservoir fluids properties contribute to further challenges with some area infamously produced high viscous heavy oil that altering the reservoir transmissibility hence the leak off behavior during fracture treatment, also later production period prone to wax and emulsion problems. Both the original formation water and injected water breakthrough from nearby injector wells are prone to scale precipitation that restrict hydrocarbon flow in reservoir and tubular.

New method of calculating reduced pad volume percentage to lower post fracture polymer concentration impact and or to achieve Tip Screen Out fracture placement has been implemented in several treatments. The reduction on fracturing fluid polymer gel fluid concentration (gel loading) has also been implemented on this campaign, resulting in better flowback clean-up process. Scale precipitation study and available inhibition techniques has been evaluated for future strategy. Proppant flowback control were known issues post fracture treatment, study on several proppant flowback control techniques has been done, as the outcome the utilization of self-consolidated proppant tailed-in will be implemented on future treatment.

This paper illustrates the continuous study and meticulous planning of design execution process of hydraulic propped fracturing, offering resolution to multiple challenges as mentioned earlier. Several strategies have been successfully implemented as part of the resolution, while some of the techniques are planned to be deployed in the future as part of continuous learning curve. The general outline of the methodology cycle can be viewed on figure 1 below. The scope of hydraulic propped fracturing campaign is covering both oil producer wells and water injector wells within South Sultanate of Oman Salt Basin to Central platform.