Tunu Field is one of the biggest fields in Mahakam Delta, East Kalimantan, Indonesia. In the past few years, new infill wells had taken an important role in Tunu Field for sustaining the field potential and maintaining the perforation portfolio. However, finding an attractive new well at this stage has become very challenging. Apart from limited wells resources, current low oil price environment has also led to significant reduction of drilling activities. Therefore, the existing perforation portfolio is becoming the backbone for maintaining the field potential and needs to be managed in an efficient and detailed manner.

As the perforation portfolio declining in-consequences of less drilling activity, any possible effort to optimize the existing perforation portfolio needs to be done. Therefore, dedicated project were set up to re-evaluate all possible gas reservoirs in Tunu Shallow Zone (burial less than 2500 mSS) which were logged with minimum Gamma Ray and Resistivity logs. Each of these reservoirs was evaluated by implementing recently in-house developed interpretation technique called RGSA.

RGSA (Resistivity to Gamma Ray Sliding Analysis) is an advance method utilizing Resistivity and Gamma Ray logs to create regression curve from RT-GR function in every 100 m interval. RGSA value substracted by RT values resulting curve called RGSWA (Resistivity to Gamma Ray Sliding Window Analysis). This RGSWA value will be positive in hydrocarbon interval and negative in water interval.

During this project, possible gas reservoirs (278.5 m of netpay) which are initially considered as non perforated reservoirs candidates had been evaluated. Eventually, 168 m of netpay (60% of the total evaluated netpay) were moved to perforation candidates and taken into account as future perforation portfolio. This project shows that old data can bring additional values when they are re-evaluated by new developed techniques and methods.

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