Low Salinity Water Injection North Mahakam Sangasanga Field Case Study

Abstract

North Mahakam Sangasanga is one of the mature oil fields in onshore Kutai Basin, East Kalimantan. The field was discovered by NIIHM – a Dutch oil company in 1897. The field comprises over 100 hydrocarbon accumulations in deltaic sands. Hydrocarbon accumulations are found at depths as shallow as 100 mSS and continue down to 1800 mSS. Low Salinity Water injection has been
performed since 2008 with an extraordinary results. The paper intends to describe the success story of this secondary recovery by low salinity water injection application in North Mahakam Sangasanga field main zone, which has successfully increased the oil recovery.

The water from shallow reservoirs is produced with electrical sub-submersible pumps or sucker rod pumps and directly pumped into the water injection network connected to water injector wells with a wellhead pressure of 250 psi. The water injection rate is 300 to 2500 bwpd from 54 active water producers. The water production and injection rate evolve over time following the reservoir management practice and well-producer availability. Currently, this water injection is resulting in oil production of 1700 bopd.

Monitoring and observation of the performance of water injector and oil producer wells are performed daily. Wellhead data is regularly checked and recorded. On the reservoir basis, monitoring has been done regularly by controlling the material balance of the reservoir by creating VRR so that water injection allocation and injection recommendation can be regularly updated., Some reservoirs are expected to have oil recovery up to 40%. A progressive development plan embraced this excellent result. Following the success story, an ongoing development study on the low salinity water injection application is initiated for 6 selected reservoirs in North Mahakam Sangasanga Field.