Design, Characterization and Implementation of Emulsion-based Polyacrylamides for Chemical Enhanced Oil Recovery

Abstract

Summary Polymer flooding is a widely used chemical technique used to enhance or speed up oil recovery from brown or green fields. Polyacrylamides used in chemical enhanced oil recovery processes can be supplied either in powder or inverse emulsion forms. The latter has several benefits for offshore deployment including smaller equipment footprint for dissolution and easier transportation to the site compared to the products in solid form. However, the emulsion is a multi-component system that requires much more attention during the formulation and the implementation than the polymer in powder form; the surfactant package must be adapted to the brine used for inversion (temperature and salinity) in order to allow a perfect release of the macromolecules and a good dispersion of the oil droplets to avoid injectivity issues. Moreover, depending on the field conditions and the dosages that are used, the interactions between the components of the emulsion and the crude has to be studied. This paper reviews the basics of emulsion formulation and design along with the best practices for evaluation in the laboratory. Basic inversion procedures for rheological evaluations, filtration tests and oil droplet size analysis are described. An attempt is made to list relevant tests that can quickly allow to discard bad formulations. A quick review is presented on the propagation of emulsions in porous media along with the possible interactions between the components of the emulsion and the reservoir. This is illustrated with several core floods performed using Bentheimer cores where pressure profiles, resistance factors and residual resistance factors as well as mitigation techniques are carefully studied in various injection conditions (low and high temperature, with or without crude oil) and compiled with other laboratory tests such as droplet size measurement to isolate the contribution of each component. The discussion is concluded with engineering and logistic aspects to discuss the proper implementation of such product in the field.