Development of improved mobility control agents for surfactant/polymer flooding. Second annual report, October 1, 1979-September 30, 1980

The objective of this laboratory work is to develop improved mobility control agents that are more effective than the commercial polymers currently used in this process. During the second year of the project, the baseline testing of commercial products was completed. These baseline tests with polymers include studies on mobility control, retention, and shear degradation in Berea cores, the effect of common ions on rheological properties, thermal stability, microbial degradation, and surfactant-polymer interactions. These data are used for comparison of the commercial agents at standardized sets of conditions, and are also used to evaluate new, modified, or improved polymers. Work was also initiated on the synthesis, characterization, and preliminary screening of new and modified polymers. Testing of these analogs provides systematic correlations of polymer performance with polymer structure. This preliminary testing consists of measurements of shear degradation and viscosity loss in NaCl brines by the use of a simplified screening procedure. To date, a number of potential structure-utility relationships have been observed. Solution viscosities of all nonionic polymers tested are essentially insensitive to changes in NaCl concentration. Increasing the charge-to-mass ratio (degree of hydrolysis) of either polyacrylamides or N-alkyl analogs enhances the ability of these polymers to build viscosity in low salinity NaCl brines. However, such polymers are increasingly subject to viscosity loss as the salinity is increased. Above a certain critical molecular weight, polymers become more susceptible to shear degradation. Many of the polymers that possess stiffer backbones exhibit improved brine and shear stability. The results of these studies will be used to develop an improved mobility control polymer in the next phase of this project