In 1988 a hydrocarbon miscible water-alternating-gas (MWAG) pilot was initiated in the Kuparuk River field, on the North Slope of Alaska. Project decline curve analysis showed a significant response to the MWAG process. The field data alone, however, could not be used to accurately project the ultimate performance of the process. A systematic, integrated approach to reservoir modelling was used to evaluate the MWAG process performance. Finely gridded one dimensional (1D) models were used to evaluate the process mechanisms. Then fine and coarsely layered 2D and 3D compositional models were used to evaluate the process efficiency. The areal effects, including faulting, were then incorporated by using a 3D, coarsely gridded, multi-well, modified black oil (MBO) model. The 3D, site-specific, model was history-matched for the waterflooding period. The miscible food performance was then predicted using a tuned MBO parameter and compared to the field performance. The 3D MBO model predicted that the ultimate incremental recovery would be 11% for a 30% HCPV slug. The model indicated that the miscible process can accelerate production of the waterflood reserves. The model was also used to evaluate the effects of total slug size, maturity of the preceding waterflood, and WAG ratio on the process efficiency.

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