Abstract
Brown field rejuvenation has always been one of the yardsticks of any operator to provide that additional support to make up for the decline in national production. Field B in Sarawak offshore of Malaysia has highly compartmentalized stacked reservoirs producing since 1980s. A few reservoirs which were on depletion drive, had been depleted but with low recovery factor and becoming idle after about 30 years of production in late 2010. With most of the major reservoirs having strong aquifer support getting into high water cut, the field production declined significantly then. In 2014, the first successful natural Dump Flood injection in Malaysia has increased oil recovery by about 6% till date in one of these depleted reservoirs at low cost. This paper details the lessons learned of Dump-flood management which included well stimulation to improve injection and timely reservoir surveillance, with choke optimization in producers to improve production. Since then, based on this success, several dump-flood water injection projects have since been initiated which improved production. MPLTs which helped to understand reservoir continuity and injectivity effectiveness, prompted the operator to evaluate forced water injection from surface for some these reservoirs. The objective of this paper thus explains the steps taken to learn from Dump-flood to initiate Forced Water Injection and thus reduce waterflood risks with phased exposure to cost.
The FFR study that followed, identified redevelopment opportunity in one depleted reservoir with significantly high STOIIP, but having a low recovery factor. In 2022, one idle well in this reservoir was converted into a dump flood injector, but achieved low injection rate, thus low incremental production. With injectivity achieved and production injection response being monitored for few years, initial understanding on risk mitigation of water injection in this reservoir was understood. Leveraging on this experience, based on a history matched reservoir model, forced Water Injection including the usage of the existing Dump-flood well as a forced water injector with few infills have been proposed to improve waterflood recovery by additional 12%. Portable Water Injection Module has been considered to reduce overhead CAPEX.
This paper thus provides the stepwise methodical approach to de-risk water injection projects in mature assets by steadily building on the success of low-cost pressure maintenance options like dump-flood and progressing into Forced Water Injection to increase the hydrocarbon recovery, reverse the production decline and prolong the economic asset life with minimal risks and phased investment.
