Abstract

Polymer and alkali-polymer (AP) flooding are investigated in laboratory corefloods for potential application in a 2000 cP – 5000 cP heavy oil field. An augmentation of oil recovery is noted with the addition of very low concentrations of partially-hydrolyzed polyacrylamide (HPAM), either in secondary or tertiary (i.e. after waterflooding) injection. However, increasing polymer viscosity from 3 cP to 60 cP does not significantly change recovery from two pore volumes (PV) of tertiary polymer injection. Injection of alkali with polymer either in tertiary mode or subsequent to polymer injection yields a significant increase in oil recovery, and is accompanied by a drop in pressure gradient when it follows a polymer slug of similar viscosity. Existing scaling groups for viscous instability are investigated and corefloods in this study and others are found to be in the transition zone or the pseudostable region, while field floods are all in the latter. Growing evidence suggests that polymer flooding can be economically applied to very viscous oils, despite the pessimistic predictions of currently available scaling groups.

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