The proposed revitalization of the Bokor field is affected by many surface-facility constraints as well as the subsurface complexity of laminated stacked reservoirs. Such complex problems require a truly integrated multidisciplinary methodology using a decision-and-risk- assessment approach to screen development options. This paper presents the process adopted and used to screen and rank the various options.
Any field redevelopment needs to begin with an identification of system bottlenecks and proposals to remove them, but often this is only considered at a facilities level. In proposing a revitalization plan for the Bokor field, the joint Petronas Carigali Sdn. Bhd (PCSB)-Schlumberger team had to develop a complex decision-making process to select an optimal development plan that would solve the constraints while minimizing unit technical operating cost (UTOC) and maximizing production.
Often, brownfield redevelopments are limited to maximizing existing facilities (slots, processing plant). However, in the case of Bokor, essentially no additional oil can be produced without an impact on existing production (lack of gas lift, lack of export compression). Thus, an approach was required that not only solved the existing bottlenecks but also allowed for sufficient additional capacity to sustain a cost-effective revitalization plan. The process had to be iterative, assessing the risks and uncertainties of each approach and its economic impact.
The solution was an approach that considered each reservoir target by discounted cumulative oil, thus producing a ranked list of opportunities that could be added together to form any development scenario. Hence, rather than running a reservoir simulation on each development case, this approach allowed multiple facility development options to be tried quickly. Each development scenario was then analysed using a tornado diagram. From this diagram was prepared a decision tree that gave the most likely outcome. This approach allowed options as diverse as subsea tiebacks to full integrated platforms with a high number of electrical submersible pumps (ESPs) to be risked and ranked equitably within a reasonable timeframe.