Sanga-Sanga Block is located onshore of the Mahakam delta, in East Kalimantan Indonesia and operated under Pertamina Hulu Sanga-Sanga. Nilam field, one of assets in Sanga-Sanga Block was discovered in 1974 with 75 km length. Nilam field was interpreted as the extension of Badak Handil Anticline Structure. The first well, NLM 1 was spudded on 8 July 1974 and put on production 9 years later due to waiting on surface facility. Early production was 22 MMscfd and flow directly to Bontang. At present, Nilam has reached a mature stage of its life where 364 wells drilled. The productions are continuing declining and currently 98 wells online and deliver approximately 23 MMscfd and 1800 BOPD.

There are 3 components to generate the production; they are base, rigless and new well program. New well program is main contributor to Nilam production. However, since oil price start to drop in 2014, drilling activity becomes decreased and consequently, rigless activity become the main backbone to arrest production decline. Aggressive rigless program is required to maintain Nilam production. Since 2010, total of perforated zones are 1323 and by the time, thus remaining zone candidates for rigless are decreasing. To face this challenge, integrated subsurface review has been conducted to assess several strategies to create new opportunity in delivering Nilam production. The strategies are; unlocking the hidden potential from by passed and unprognosed zones in existing well and campaign of complex rigless program to access the potential zones.

In early 2018, these strategies has already applied and already contributed 4.42 Bcf and 164 thousands of barrel oil to Nilam Field. The success ratio is 73%. It helped to sustain Nilam production and maintain the decline rate. In summary, these strategies have successfully unlocking hydrocarbon potential and maximizing recoverable reserve in existing wells which resulted in extend the field life. This paper will describe the success story to unlock gas and oil reserve in complex environment especially at Nilam Field.

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