Polymer Flooding-A Current Appraisal

Abstract

On the basis of results from a substantial number of field projects, polymer flooding has been found to be successful over broad ranges of polymer flooding has been found to be successful over broad ranges of reservoir conditions and fluid characteristics. But it is a complicated process to design a polymer flooding program, and the many variables process to design a polymer flooding program, and the many variables involved require sophisticated calculations that are best handled with a computer. Introduction Papers by Pye and Sandiford in 1964 established Papers by Pye and Sandiford in 1964 established the fact that the mobility of the brine used in waterflooding was greatly reduced by the addition of very small amounts of hydrolyzed polyacrylamide, a water-soluble polymer. This reduction in brine mobility resulted in greater oil recovery than that attributable to conventional waterflooding. Many additional papers sustaining and extending this information have since appeared in the literature. To date, very little field information has been available from which to draw conclusions regarding the most suitable reservoir and fluid characteristics for polymer flooding applications. The purpose of this polymer flooding applications. The purpose of this paper is to present basic conditions and test results paper is to present basic conditions and test results for a large number of polymer flood projects and to examine the ranges of some of the more important parameters within which success has been achieved. parameters within which success has been achieved. In addition, the effects of variations in several important reservoir and polymer properties upon polymer flood recovery are illustrated with the aid polymer flood recovery are illustrated with the aid of a computer program. Such effects are not readily observable by field testing. Field Test Results Tables 1 and 2 list reservoir and fluid properties for 61 polymer flood projects begun between 1964 and mid-1969. All projects with which we or our colleagues have been associated are included. We believe that the polymer used in these 61 projects represents more than 95 percent of all the polymer injected to date as a mobility control agent in flooding. Although the individual projects vary greatly in size, the combined amount of polymer used amounts to several million pounds under commercial rather than purely experimental conditions. Specifically excluded from these tables are those projects employing polymers on a small-volume, short-term basis for injection profile correction, and projects where polymer solutions profile correction, and projects where polymer solutions are used to displace miscible fluids. Also excluded are previously reported research pilot tests. previously reported research pilot tests. Table 1 lists 29 projects from which significant information concerning the applicability of the polymer flooding process can be obtained. Table 2 lists polymer flooding process can be obtained. Table 2 lists 32 additional projects from which such conclusions cannot be drawn either because of some gross reservoir defect rendering the reservoir unsuitable for any displacement process or because the project was started too recently to be interpreted. In each table, most of the more important reservoir and fluid characteristics are listed together with the recommended polymer flood plan. The sequence in which the polymer flood plan. The sequence in which the projects are listed is determined by the stage of projects are listed is determined by the stage of depletion (Column 14) at which the project was begun that is, P indicates a start near the end of primary; ES, early secondary; LS, late secondary; and T, tertiary. Test results are indicated in Column 20 and are defined both in the footnotes of each table and in the following paragraph. JPT P. 675