Improvement in areal sweep efficiency

the role of polymer here is to improve the mobility ratio between the fluids by either increasing aqueous-phase viscosity or reducing the aqueous-phase effective permeability (see Chapter 5) or both. This lowered mobility ratio will improve both the linear and areal displacement efficiency, thus leading to improved oil recovery. 

The effect of areal sweep improvement using polymer will be illustrated using results from two laboratory/simulation studies (Slater and Farouq-Ali, 1970 Patton etal, 1971). Slater and Farouq-Ali (1970) presented results of both miscible and immiscible brine and polymer floods in five-spot laboratory packs. Conventional homogeneous five-spot models and packs with different 

Patton etal. (1971) presented methods for calculating polymer flood recoveries in both linear and five-spot systems. The method they proposed for the five-spot case was a generalisation of their 1-D method in which very simple triangular streamtubes were used to divide up the area. They validated their model by matching the waterflood five-spot results presented 

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If increased water viscosity could be economically realized, marked improvements in areal sweep efficiency, as discussed by Caudle and Witte and others, would be realized in field operations. Similarly, the improved mobility ratio would bring about increased recoveries by correcting permeability distribution problems as discussed by Stiles and Dykstra and Parsons, and improvements in displacement efficiency would be obtained as recognized by Buckley and Leverett and Welge. ... 

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