Conventionally, for an oil development field with the risk of water breakthrough during its life time of production, a cased hole with perforation method will usually be chosen. This is a proven method of completion strategy that enable an effective way to provide proper water isolation.
Project B is an oil development project in Malaysia with 3 wells in total, which were drilled and completed by early February 2019. During the early stage of the project at Front End Planning, offset well data suggested that there are 2 target zones of hydrocarbon in the field being separated by a thin layer of shale (3meters), dividing them into upper and lower lobe of oil reservoir. It was expected to see a water reservoir below these two reservoirs and hence, the proposed completion strategy was to perform Cased Hole with Perforation and Gravel Pack. Further studies between Production technology and Completion team had raised the concern on the integrity on the water isolation due to the shunt tube system used for the gravel pack job.
To effectively isolate cross flow between the upper and lower lobe of the oil zone and delay the water break through from the lower water reservoir section, project team modified the completion strategy from Cased Hole Gravel Pack to Open Hole with Stand-Alone Screen (OHSAS). Hybrid Swell Packers will be installed at the thin shake layer to provide the zonal isolation.
The completion strategy modification had simplified not only the offshore completion operation, but also the logistic planning and footprint allocation due to lesser equipment required. Total cost saving had been achieved at USD 1.44 Milliom with around 2.4 days reduction on completion operation timing.
This paper will discuss the rational to modify completion strategy, cost comparison and operational sequence between these 2 methods of completion. This paper will also cover the challenges, limitation to deliver the well.