The paper describes an optimisation methodology used to aid development planning for the A-18 block in the Malaysia Thailand Joint Development Area (MTJDA). Development of this block is complicated by the large areal extent, gas residing in up to fifteen different major reservoir sequences, large depth range with the deeper sequences being HPHT intervals, and CO2 contents varying from 1 to 60%. An optimised field development plan has to maximise economic value from a volume based gas sales agreement which generates a heating value based revenue stream linked to CO2 level, and prioritises condensate production. The interplay between gas and liquids considerations and a myriad of potential platform and development drilling options within a PSC environment makes the selection of an optimum development scenario difficult.
The paper describes how a decision framework was used to maximise the economic value of the asset. This custom built software automatically generates possible development scenarios, and then uses branch-and-bound and outer approximation solution techniques to analyze and efficiently "prune" the scenario tree to eliminate sub-optimal candidates. The results illustrate the effectiveness of applying optimisation technology to this complex asset, as development plans can be quickly and robustly constructed for different GIIP and recovery scenarios and for different objectives such as maximising sales gas volume or NPV.