This paper summarizes the core analysis data and the reservoir simulation history match of two Zone 4 cores in areas of Prudhoe Bay that were produced by different recovery mechanisms. It also describes the process comparison studies and the updip waterflood and miscible gas flood field-tests which resulted from those studies. One Zone 4 core was taken in the gravity drainage area and one Zone 4 core was taken in the waterflood/WAG area. Both cores were history matched with a reservoir simulator to reproduce the measured oil saturations and to determine the ultimate recovery potential of the process currently being employed. The success of the simulations in matching the actual core data increased our confidence in the accuracy of the ultimate recovery forecasts. Additional simulations were run to evaluate converting part of the updip portion of Zone 4 from gravity drainage to some form of water and/or miscible gas injection. These simulations indicated that the gravity drainage process was leaving high oil saturations behind the gas front that could not be produced economically because of excessive gas-oil ratios (GORs). Both water injection and miscible gas injection mobilized large volumes of oil and dramatically reduced GOR. This behavior has been observed in early field-test results.

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