AB field has undergone secondary recovery of water injection for pressure support and sweep efficiency improvement. From proactive surveillance program, it was further discovered that AB field performance is improving without water injection. Pilot shut-in water injection study initially commenced post 5 years of production. From the pilot water injection shut-in, surveillance data was used for thorough analysis to conclude that secondary recovery through water injection will reduce field recovery due to early water out coupled with moderate to strong aquifer strength.

Close pressure monitoring, surveillance database, and other diagnostic plots used to gauge the water injection healthiness in AB field. Reservoir modelling was built to validate the implication of water injection secondary recovery to the field. Complete surveillance data and gathering method will be presented in this paper to permit readers to replicate the analysis prior to conclude secondary recovery type of mechanism, typically water injection, is beneficial to the field or proven otherwise.

Pilot shut-in water injection has proven the following: (1) It was observed that AB field pressure still maintains above the pressure target of initial Field Development Study, (2) Watercut performance has significantly increased post pilot water injection shut-in, (3) no substantial impact on the reserves loss, while in contrast, water injection stoping will improve recovery due to delaying the wells watered out time. For this marginal field of AB, an incremental of 0.8-1.7 MMstb reserves recovery will contribute to higher recovery factor. This is also due to the moderate to strong aquifer strength against weak to moderate aquifer strength anticipated earlier in FDP.

Casehole contact logging was conducted at two wells in the field to monitor the contact movement. From all the observation and analysis conducted, AB field was further optimize by the Reservoir Management Plan (RMP) revision. Lesson learned from the case study will enhance others' understanding and view prior to deciding on secondary recovery method to any field. RMP study should be updated as the production continues and once more data is acquired from the right surveillance program.

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