Integrated Reservoir Management Helps to Arrest Decline and Increase Production Significantly - A Case Study of Angsi

摘要

With lesser new discoveries, integrated reservoir management has become the key tool to assure committed production. In Angsi B reservoir, injection for pressure maintenance was initiated with start of production. Simultaneous water injection at the southern flank and also at GOC to the south was initiated with the plan to arrest gas cap expansion and sandwich oil for better recovery. Injectivity issues, unavailability of required injection volume, increasing offtake led to variable pressure decline in the reservoir. Decline in production more than predicted was thus observed due to resultant uneven sweep. Preferential expansion of the gas cap to the north led to wells getting high GOR resulting in further decline. Well integrity issues surfaced which led to certain wells to be closed prematurely adding to reservoir management problems. This led to critical well and sector performance analysis to understand the reservoir dynamics. Study indicated resaturation loss of reserves at the prevalent pressure maintenance strategy. Various alternative pressure-production plans were evaluated to prevent reserve loss and decline in production. The best plan included a change of injection strategy, temporary closure of HGOR wells, profile modification in injectors and producers, a structured reservoir surveillance programme and integrated discipline weekly meeting to monitor and guide this change of reservoir management. The results were very rewarding as it not only helped in arresting pressure and preferential gas cap expansion, but also arrested and reversed production decline. This paper details how the alternative reservoir management approaches were evaluated within current constraints to agree on the current reservoir management plan, what were the different strategic actions taken, monitored, evaluated and revised to effect the change. Convinced of its effectiveness, similar integrated reservoir management approach has been initiated in another reservoir of Angsi which already shows indication of decline getting arrested.