Assessment ofl-WAG for Optimnm Recovery from a Heterogeneons Reservoir Offshore Terenggann, Malaysia.

\Vater alternating gas, \VAG seems to be the most practical EOR for Malaysian
fields considering the abundance of C02 gas and the availability of treated seawater for
injection. The injected seawater is used to increase the macroscopic displacement
whereas the injected C02 gas is used to mobilize the residual oil to further enhance the
sweep at microscopic level. The present study evaluates the influence of voidage
replacement ratio (VRR) and WAG cycles to the incremental recovery factor. A
dynamic model was developed by using Eclipse 100 to assess the incremental recovery
from the implementation of WAG on a heterogeneous, non-apparent fluid contact oil
reservoir offshore Terengganu. The study found that the predicted incremental recovery
of 7% was insensitive to both VRR and WAG cycles. This incremental recovery was
almost the same with the one obtained from the secondary recovery. This could be due
to the complexity of the reservoir structure itself which requires further refinement on
the locations of the injectors' perforation. Early gas breakthrough was observed in
almost all simulated WAG cycles cases that ranged from 3 to 12 months and VRR cases
that ranged from 50% to 150%. Therefore, the present study recommends WAG
optimization involving assessment of the individual producing well performance.