This paper covered success collaboration between sub-surface and surface engineer in managing mature offshore oil field in Asri basin, Southeast Sumatera, Indonesia. The main objective was to maintain oil production rate and increase ultimate recovery in the most efficient way, technologies that applied strictly selective to minimize risk while optimize oil production. Common problem faced are extremely high water cut and high operating cost due to massive artificial lift application.

The three effective tailored methods in this paper are: (1) Determining residual oil volume and locating the position. Material balanced calculation and core analysis are the tools to determining residual oil volume, while tracer test conducted in order to determine the location and distribution of the oil remained. (2) Surface facilities assessment, facilities are ageing and need to refurbished/replaced after 27 years of production, it creates limitation in operation area. (3) Potency screening, in this phase we focused more on technical difficulties assessment, both sub-surface and surface (from method 1 and 2) result analysis are combined to determined technology selection. After that we put into action, and do evaluation on cost spending and production performance.

Efficiency is the key issue in mature field redevelopment, solid collaboration between sub-surface and surface team lead to satisfying result to reduce production decline. Several case studies have been included in the paper to highlight the detail project: (1) Idle wells, to increase production it is very important to increase well count, the wise way is by utilize existing wells in idle condition. Mechanical failure, water out, formation damage, low potential, etc. are cause of idle wells, in the last 3 years 13 wells successfully back to production. (2) Modified completion fluid, one of technology applications with ‘breakthrough’ result. In depletion drive reservoir we found lot of residual oil potency that can't be sweep, the solution is to reduce oil viscosity around wellbore and increase the mobility using modified completion fluid, and the result is beyond expectation. (3) Water injection redirection, based on performance evaluation and tracer injection analysis, several injectors is ineffective due to reservoir connectivity and mechanical issue, this project creates new sweep pattern and successfully increase recovery factor. (4) Mechanical loss handling, we found big losses contribution from tubing leak, after laboratory and field analysis losses can be reduced.

Technology and integration of sub-surface and surface capabilities are vital to unlocking the full potential of mature assets and achieving higher recovery factors. Application of the three tailored methods was considered as an appropriate way to approach and manage a complex mature field redevelopment.

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