Offshore Noth West Java (ONWJ) production sharing contract block has been producing since 1970s. The block consists of many oil and gas sturctures, both clastic and carbonate reservoirs. The era of "easy reservoirs" is almost to an end as the fields are maturing over time. Long term development plan is desired to sustain the ONWJ block oil and gas production. The development strategies are focusing on low resistivity development, bypassed oil as the low hanging fruit, add reserves from deeper reservoir and shallow gas development.

Bypassed zones exploitation contributes in sustaining ONWJ oil and gas production. Drill stem test data back from the 70s was revisited, well log and correlation was reviewed to find the proven "low hanging fruit" and possible reserves. Sidetracking well to twin the proven exploration well or simply recomplete existing wells were done to add reserves.

Low resistivity reservoir was considered unattractive or even identified as non-reservoir in the early life of the block exploitation. However, with thourough evaluation and suitable hydraulic fracturing treatment, the reservoir contributes significantly in sustaining production decline. These zones become one of the keys in future development

The gas demand from the near market is continue growing with attractive price. It becomes one of the drivers to find more hydrocarbon gas. In the old days, shallow gas became one of hazard that need to be mitigated. Recently, as the major gas reservoirs continue on its depletion, this shallow was produced; converting from hazard to reserves.

Above strategies were successfully applied within fields in ONWJ block and doubled its production to the level of 43,000 bopd and 180 mmscfd within less than 5 years since operated by Pertamina Hulu Energi (PHE) ONWJ. This paper will discuss subsurface strategies to achieve and sustaining hydrocarbon production and related case studies of several fields in Offshore North West Java. It will also discuss the learning curve for future strategy and application in further redevelopment.

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