Novel Redevelopment and Economically Promising Approach Doubled the Recovery for a Carbonate Reservoir Unit in Abu Dhabi Field

Abstract

Abstract Objectives/Scope One of the reservoir units producing from a carbonate reservoir in Abu Dhabi field since 1980 is characterized by having relatively good rock quality to the South with deterioration in rock quality towards North. Inverted nine spot gas injection pattern started for this unit since 1992. Despite all the efforts to improve the recovery from this reservoir unit, still the recovery factor after 40 years of production did not exceed 15 %. This is in addition to the inability of the unit to sustain its production target. Methods, Procedures, Process A novel mixed pattern gas and water injection scheme proposed to improve this reservoir unit recovery. First, replace the existing gas injectors by water and add new water injectors in good-quality area to ensure good water injectivity. Second, reduce gas injection or add new gas injectors if needed in the poor-quality area to keep a minimum VRR of one splitting equally between water and gas injection. We developed a novel line drive pattern approach for locating the new water and gas injectors which we call it "Produce Shallow and Inject Water Deep (PSIWD)" for water injectors and "Produce Deep and Inject Gas Shallow (PDIGS)" for gas injectors. All the injectors are horizontal to imitate bottom aquifer for PSIWD in the good-quality area and gas cap for PDIGS in the poor area. Similarly, all the producers are horizontal located at the top of the reservoir in the good-quality area and at the bottom in the poor-quality area to reduce the water and gas early breakthrough. Results, Observations, Conclusions This approach simulated on a full field scale and proved its efficiency in increasing the recovery factor to 40 % and maintaining longer plateau for 18 years. On top of this, it is economically promising by reducing the OPEX for gas injection to 1.2 Billion USD savings that can reach to 2.4 Billion USD savings in the next 30 years with the application of full water injection (PSIWD) in both good and poor-quality areas. Novel/Additive Information Unlike the conventional line drive pattern with injecting and producing within the oil column, our proposed mixed line drive pattern water and gas injection with the application of PSIWD in the good-quality area and PDIGS in the poor-quality area has tendency to reduce the gas and water breakthrough thus ensure better sweep efficiency and higher pressure support. On top of this, the proposed development approach shows 40 % reduction in the cost per barrel compared to the current development approach due mainly to the OPEX reduction for the gas injection and the incremental increase in recovery.