The Reagan reservoir of the Sleepy Hollow Field in Red Willow County, Nebraska is an ideal polymer flood candidate. It has viscous oil in a high permeability sandstone with high oil saturation and fresh water available for injection. Laboratory and field testing were used to evaluate emulsion polyacrylamide polymers for injection. Laboratory core tests were of marginal use due to the lack of representative core samples. Fractional flow analysis was used as a screening tool and reservoir simulation studies were used to predict polymer flood performance. A field injectivity test showed the polymer to have much more effect in the reservoir than in the core tests. Based on these results, and a concern that injectivity loss could be excessive, a conservative selection was made of polymer molecular weight and solution viscosity. The polymer flood was initiated on February 14, 1985. An extensive quality control program was implemented to insure compliance of bulk emulsion shipments with specifications and to insure that fluids leaving the mixing plant and throughout the system were of suitable properties. Injected fluid properties were maintained within close tolerances and this effort contributed to the low loss in injection rate experienced in the flood. Swab-back sampling and pressure transient tests were used to measure the properties of injected fluids in the reservoir and to confirm that shear degradation losses at the sand face were not excessive. Water-oil ratios have declined from 45 to 17 in the polymer flood area, which contains 10 injectors and 45 producers. Polymer breakthrough has not been excessive and no emulsion problems have been encountered in the produced fluid system. Corrosion has increased since polymer breakthrough and there is indication of partial plugging of producing wells. Beginning in 1986, due to the downturn in oil prices, efforts were made to lower operating expenses by reducing injection rates and polymer concentration. These changes have significantly reduced operating expenses and have consequently enhanced the economics of the flood. Results to date indicate the flood will be a technical and economic success.

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