Abstract The Seligi is a large oil field comprising a multi-closure anticlinal complex with the major reservoirs having relatively thin oil columns with large gas caps and aquifer of varying strength. The field contributes about one third of Esso Production Malaysia Inc.'s (EPMI) operated production and started to decline in 1995. A comprehensive depletion management study was initiated in 1997 to mitigate production decline and maximize ultimate recovery. This paper describes the challenges faced in managing this large resource, technologies used to address these challenges and some initial results from the studies. Early accomplishments include revised gas injection strategies, an inventory of wellbore opportunities, an optimized well / gathering system capacity, and infill / new development programs. Some of the above opportunities have been successfully implemented in the field; these have helped in mitigating production decline and increasing reserves capture.