Polymer Flooding Technology Yesterday, Today, and Tomorrow
Authors: Chang H.L. 
Published: December 2007

Polymer flooding, an augmented waterflooding method, has been evaluated Polymer flooding, an augmented waterflooding method, has been evaluated comprehensively in the laboratory and extensively field tested. This paper reviews past industrial experience, appraises current technology, paper reviews past industrial experience, appraises current technology, defines screening guidelines for field use, and discusses the future of the process.

Introduction
The petroleum industry recognized the problem of inefficient oil recovery by conventional (primary and secondary) recovery methods in the early 1900's. Since then, extensive research has been conducted on improvement of displacement and sweep efficiency in petroleum recovery. Many different processes have been designed to improve displacement efficiency by reducing residual oil saturation. However, polymer flooding was designed to improve sweep efficiency by improving the mobility ratio. Muskat first pointed out that fluid mobilities would affect waterflood performance. In 1949-50, Stiles used permeability and capacity distribution in waterflood permeability and capacity distribution in waterflood calculations and Dykstra and Parsons showed the effect of permeability variation and mobility ratio on recovery. permeability variation and mobility ratio on recovery. Aronofsky and Ramey discussed the mobility ratio and its influence on flood patterns during water encroachment in 1952 and on injection and production histories in a five-spot waterflood in 1956. In 1954, Dyes et al. presented studies of the influence of mobility ratio on oil presented studies of the influence of mobility ratio on oil production after breakthrough. Later, Caudle and Witt production after breakthrough. Later, Caudle and Witt (1959) and Barnes (1962) suggested improving waterflood sweep efficiency by increasing water viscosity. However, it was not until 1964 that Pye and Sandiford established that the mobility of water (or brine) used in waterflooding can be reduced efficiently by adding small amounts of a water soluble polymer. Since then, significant laboratory studies have appeared sustaining and extending this information. Recently, several additional important properties the inaccessible pore volume, shear degradation in porous media, and polymer retention have been observed. In addition to the laboratory findings, field test results also have appeared in the literature. Detailed summaries of these field reports were given by Jewett and Schurtz, Sloat, Agnew, and Herbeck et al. This paper reviews the process development, discusses current status, and assesses the future potential of polymer-flooding technology. polymer-flooding technology. Process Description Process Description Polymer flooding is an enhanced oil-recovery process Polymer flooding is an enhanced oil-recovery process that uses polymeric additives at concentrations of 250 to 1,500 ppm in the flood water. The polymer solution improves the water-oil mobility ratio; this results in the reservoir being swept more completely than if flooded with water not containing additives to reduce mobility. Currently, two types of polymers are used (1) a synthetic polymer classified as a polyacrylamide (partially polymer classified as a polyacrylamide (partially hydrolyzed), and a biologically produced polymer known as xanthan gum. In addition to increasing viscosity, polyacrylamides alter the permeability of the reservoir rock; this also lowers the effective mobility of the injected water. When the permeability of reservoir rock is reduced, a lower polymer concentration can be used to gain equivalent polymer concentration can be used to gain equivalent mobility control.