Reservoir management of the mature Windalia waterflood field by optimising water injection allocation

Abstract

Barrow Island’s Windalia reservoir is Australia’s largest onshore waterflooding operation, developed in 1965 with waterflooding starting in 1967. The Windalia reservoir is highly heterogeneous and geologically complex, showing low permeabilities and extensive fault networks. Presently, injection rates are constrained by water availability because of aging source water facilities and increased injector failures because of high integrity risks, highlighting the importance of optimised distribution of injection volumes. Static allocation of injection water has historically been conducted on a pattern basis. This approach, however, is not grounded on the relationships between injection and production wells; instead, it honours the geometric layout of the wells. A more dynamic approach was required to account for the changes in status of injectors and water availability that are often encountered in mature waterflood systems. The successful completion of the Windalia capacitance-resistance model (CRM) was leveraged to develop a comprehensive ranking system of all capable injectors, quantifying short-term normalised oil response to maximise the oil production achieved for a given volume of water injected. Improved understanding of injector-producer communication has also provided the ability to extract the maximum value from limited injection water volumes and has the potential to reduce water cycling and the associated water-handling costs. It can also improve the ability to identify and prioritise workover and stimulation opportunities. This work describes the advances in reservoir management capabilities by quantifying the relationships between injector-producer pairs and the dynamic allocation of injection volumes.