Selection Of Polymers For The Control Of Mobility And Permeability Variation At Richfield East Dome Unit, Orange County, California

Abstract

Abstract Richfield East Dome Unit (REDU) is located in Orange County, California, southeast of Los Angel The East Dome Unit contains several massive unconsolidated sand zones which were produced by depletion drive from 1920 to 1974. In 1974, a water-flood was initiated in the Chapman Zone. The performance of the waterflood has been reduced performance of the waterflood has been reduced by the highly hetergeneous nature of the Chapman sand and by the adverse water-oil mobility ratio resulting from the high viscosity crude oil present. Preliminary evaluation of various enhanced recovery Preliminary evaluation of various enhanced recovery processes indicated that the application of processes indicated that the application of mobility control polymer, coupled with selective permeability variation control treatment of certain permeability variation control treatment of certain injection wells, could improve the oil recovery efficiency of the waterflood. Extensive laboratory testing was conducted Chapman cores and sand packs to select the most applicable mobility control polymer and the most effective permeability variation control process. process. Five commercially available mobility control polyacrylamide polymers were screened to determine polyacrylamide polymers were screened to determine their suitability to REDU reservoir rock and fluids. Selection criteria included the oil recovery efficiency, polymer retention, polymer solution viscosity, and residual resistance factor. As a result of the laboratory tests, Cyanatrol WF-940S was selected for additional field testing. Three commercially available polymer permeability variation control processes were also permeability variation control processes were also evaluated in the laboratory. The ability of each process to improve the dimensionless flow rate process to improve the dimensionless flow rate ratio in parallel sand pack tests was used as the main selection criterion. A polyacrylamide treatment utilizing aluminum cross-linking was selected for additional field testing. Field tests of both the mobility control polymer and the permeability variation control polymer and the permeability variation control polymer process have been initiated in the polymer process have been initiated in the Chapman Zone of the Richfield East Dome Unit. Introduction Richfield East Dome Unit (REDU) is located in Orange County, California, southeast of Los Angeles. Figure 1 shows the location of the Richfield oil field in the Los Angeles Basin. The East Dome is one of three anticlinal domes which comprise the Richfield oil field. The field was discovered in 1919 and solution gas drive was the dominant primary producing mechanism. The East Dome area was unitized in July, 1971, with Texaco, Inc. as the operator and waterflooding was initiated in the Chapman Zone in March, 1974. The Chapman Zone, the zone of interest for this paper, is the main producing sand under waterflood in paper, is the main producing sand under waterflood in the reservoir. It is composed of a massive, unconsolidated sand which has wide variations in permeability. The 18 API gravity crude oil exhibits a high viscosity at reservoir conditions which results in an adverse water-oil mobility ratio. The combined problems of permeability variation and adverse water-oil mobility ratio impair the efficiency of the present waterflood and reduce the ultimate oil recovery. present waterflood and reduce the ultimate oil recovery. Screening of enhanced recovery processes indicated that the application of mobility control polymer, coupled with selective permeability variation control treatment, would be the most suitable process for improving the flood performance. performance. This paper presents the results of extensive laboratory testing conducted with reservoir fluids in Chapman cores and sand packs. The purpose of this testing was to select the most purpose of this testing was to select the most applicable mobility control polymer and the most effective permeability variation control process. process.