Optimized Water Management Life Cycle Strategy for a Giant Offshore Field

Water management plays a vital role in the oil and gas industry since it is an important injectant to maintain reservoir pressure in addition to being a by-product of oil crude production which needs to be separated. Optimal water management is critical for maximizing production profitability and hence minimizing total water life-cycle costs. This paper presents an integrated water management life cycle strategy for one of the largest offshore oilfields in the world. The subject field is currently injecting seawater under matrix injection mode. Reservoir souring, scale modelling, core-flood tests, etc. were conducted to evaluate water compatibility, scaling risk and water specification required for properly designing the surface facilities to process raw seawater for injection without negatively affecting reservoir performance. The field's rock quality varies in different regions: permeability is higher in the east region and gradually deteriorates towards the west area. Different water injection strategies are applied to address the variance based on lab study results: in the east part, sea water is filtered down to 2µm before injecting to subsurface to avoid formation damage. Whereas in the west part average permeability is around 1mD which poses huge difficulties in terms of water injectivity and its development. The traditional approach of wellbore cleaning and stimulation coupled with an innovative solution of removing sulphate from the seawater to reduce SrSO4 scale risk are implemented to address these sea water injection complications.