The design of a gravity dump flood well for a depleted QG reservoir located offshore in M Field was significantly enhanced by the inclusion of an Electric Submersible Pump (ESP). This resulted in 1,500 barrels of oil per day production gain from producer wells in Area 2 of the reservoir that had become inactive due to low tubing head pressures with reservoir pressure depletion.
The identification of an optimal water injector location to improve the low reservoir energy and sweep oil towards the existing producers was grossly challenged due to remote nature of existing wells from water injection facility. Significant cost implications exist for the construction of new pipelines to the Water Injection facility. In addition, the existing infrastructure is aged and degraded, creating a need for a cost-saving solution.
The challenges were tackled by implementing a pilot ESP powered dumpflood in an ideally situated injector "Xi". With this technique, a single well acts as both the producer and injector, utilizing an ESP generated pressure differential to pump water from a deep aquifer to a shallow reservoir or boost natural gravity forces to reverse pump water from a shallow aquifer to a deeper reservoir (R. Quttainah 2001). The latter option proved ideal for this application given the shallower location of the water source relative to the target oil zone.
By innovatively using Y-tool technology, the ESP reverse pumped 7,000 BWIPD at a discharge pressure of 772 psig from the upper "A" aquifer zone into the target oil QG reservoir within the same well at startup. The ESP motor was powered by a 4km electrical subsea cable to draw power from the field's Quarter Production Platform. Significant cost savings were achieved by eliminating the need for pipeline construction since water source and injection were combined in one well. Within 3-months of ESP startup, the target reservoir pressure boost resulted in the restoration of inactive wells and 1,500 BOPD incremental production gain from producers in Area 2 of the reservoir.
Following the success of the ESP powered dumpflood pilot project with initial oil production gain of 1,500 bopd and significant cost savings, a study is ongoing for a field-wide deployment of the technique in field M and 2 neighbouring fields.