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Indonesia have several Mature oil and gas fields. A mature field refer to an oil and gas field that have been discovered and produced for several decades. These mature fields present unique challenges in further development due to the large number of drilled wells and partially depleted reservoirs. This study focuses on the Mutiara-Pamaguan Field, a gas-oil field located onshore in the Sangasanga PSC, Kutai Basin, East Kalimantan, Indonesia. The field was previously operated by VICO Indonesia and is now under Pertamina Hulu Sangasanga (PHSS). The brownfield Mutiara, has been producing for over 25 years, with reservoirs characterized by complex, stacked deltaic sand lenses.

In recent years, Mutiara-Pamaguan has been analyzed and evaluated in more geological detail and has evolution and stages in placing well points for oil and gas drilling. The initial concept for developing this field focused on searching for the existence of virgin reservoirs, with a pattern of between wells of 300 meters, 500 meters, or even up to 1 kilometer, maximizing the opportunity to find new reservoirs.

However, Currently, with quite a large number of wells already drilled, the past development pattern and method will be difficult to replicate, due to closer well spacing. Currently, the field development pattern is focused on delineating layers that are proven and have sufficient pressure (not depleted) and water cut that is still low. The spacing between development wells is currently around 75 m to 300 m, with further studies and analysis being carried out for development towards the flank, at distances of more than 300 meters from the nearest well.

The pattern chosen for developing the old field at Mutiara Pamaguan has proven to be the best method to maintain production and extend the life of the field. The grid base pattern carried out from 2019 to 2023 at Mutiara Pamaguan has resulted in finding incremental reserves of approximately 38 bcf and 13 mmbo. Currently, this method continues to support well production in Mutiara Pamaguan in a stable and economically profitable manner.