Abstract

Area 8, located at east central of the Duri Field, was developed on inverted 9-spot pattern and put on continuous steam injection in 1996. Operating a steamflood in this area is quite challenging because the area was developed using a 9-spot pattern and produced commingled through long openhole completion. The consequence of having a 9-spot pattern is steam will breakthrough to the side producers more rapidly than to the corner producers because of their closer distance to the injectors. Once steam breakthrough has occurred at the side producer, it often creates a path to the side producers that prevents steam from propagating further to the corner producers. This will significantly reduce sweep and heat efficiency. To help solve this problem, a simulation study was carried out in 1996 to develop the best post steam breakthrough strategy for inverted 9-spot pattern.

The general post steam breakthrough strategy applied in Area 8 of the Duri Field is intended to divert steam to unswept zones by aggressively installing chokes at casing blow line of the side producers. The choke installation creates back pressure at the side producers and redirects steam in the reservoir to the corner producers. Isolating the steam zone at the producing wells was also conducted once the production drop. This strategy has proved to be very effective to reverse a natural production decline due to steam breakthrough and to improve sweep efficiency. 4D seismic (3D-time lapse) performed in this area supports the conclusion that better sweep efficiency is being achieved.