Natural dump-flood, a low-cost secondary recovery method was successfully implemented for the first time in the Malaysian offshore environment. The dump-flood was initiated by adding perforations in a high-pressure water aquifer and allowing water to cross-flow naturally into a low-pressure depleted reservoir. With investment of 0.4 million USD, the dump-flood has effectively increased the reservoir recovery factor (RF) while increasing the reservoir pressure by more than 300 psi despite being continuously produced.
After 30 years of production, most solution gas drive reservoirs in Field B were idle and depleted. A low-cost natural dump-flood was implemented in reservoir S2, a depleted reservoir, by converting well D-10 into a dump-flood well. The conversion was achieved by perforating a high-pressure water aquifer underneath the S2 reservoir in the same well and allowing water to naturally cross-flow into the depleted reservoir. An existing oil producer, well D-07 was selected as the offtake well that would be produced once the pressure increased. The well operations were both simple and inexpensive as indicated above.
The dump-flood initiative in the first reservoir, S2, was a complete success. A year after the dump-flood was implemented, the offtake well D-07 began to steadily produce 250 bopd compared to its earlier intermittent production. The well production increased to 600 bopd after five years. Pressure survey and production logging results confirmed the positive impact of the dump-flood. The reservoir pressure increased by 300 psi, despite continuous production throughout the dump-flood period. A reservoir simulation model indicated the dump-flood increased the recovery factor of the S2 reservoir by more than 8%. Numerous lessons learned were acquired during the implementation of this first natural dump-flood in Malaysia which serve as a reference for future application. The dump-flood in the S2 reservoir is hailed as a breakthrough, since it helps prove that secondary recovery can be implemented with minimal investment in an offshore environment.
This paper provides valuable insight into the case study of maximizing oil recovery through dump-flooding in an offshore environment. The lessons learned serve as a guideline for this simple and low-cost approach, which is highly recommended for maximizing oil recovery in a mature field, especially in today's low margin business climate.