The Dulang oilfield is located some 130 km offshore Terengganu in Peninsular Malaysia. The field is structurally complex. Production from the field began in March 1991, and oil production averaged 26 thousand STB/D. Production peaked at approximately 50 thousand STB/D.
As with other field developments in the Malay Basin, all the wells in Dulang field were completed without any sand control measures as sand production under normal drawdown or producing conditions was not expected. However, in the later stages of the field's life, a significant amount of sand production was observed. This condition gradually increased over time, resulting in reduced hydrocarbon production, additional costs for routine wellbore sand clean-outs, and platform shutdowns for surface vessel sand clean up.
To revitalize the field, a wellbore opportunity study was initiated in 1999. The objectives of the study were to 1) identify remaining reserves, and 2) identify new completion options to maximize recovery. The study identified three major scenarios that would improve oil production:
Develop by-passed reserves behind casing
Reactivate idle wells that had been closed in as a result of sand production.
Provide drainage points for undeveloped reserves.
From the proposed wellbore opportunities study, ten wells were identified for a workover campaign, and six wells were identified for infill drilling or sidetracks.
Sand control mitigation using a gravel-pack technique was identified as a requirement in the completion plan for the majority of the targeted reservoirs. However, the increase that would result in mechanical skin from sand control installation was also recognized. Hence, it was determined that the best approach for production optimization in these wells would be a combination of a sand control and a stimulation technique. Several technologies, which included frac and pack, extension pack with conductivity enhancer, and high-rate water pack (HRWP) gravel packing were identified. The use of a special completion tool was also identified to enable greater flexibility on short string selective production in multi-zone gravel-packed wells.
The combination of sand control and stimulation techniques (frac pack, extension pack and high-rate water pack) has successfully increased the productivity and prevented sand production in the Dulang wells.