A Mechanistic Integrated Geochemical and Chemical-Flooding Tool for Alkaline/Surfactant/Polymer Floods

Summary Mechanistic simulation of alkaline/surfactant/polymer (ASP) flooding considers chemical reactions between the alkali and the oil to form in-situ soap and reactions between the alkali and the minerals and brine. A comprehensive mechanistic modeling of such process remains a challenge, mainly caused by the complicated ASP phase behavior and the complexity of geochemical reactions that occur in the reservoir. Because of the lack of the microemulsion phase and/or lack of reactions that may lead to the consumption of alkali and resulting lag in the pH, a simplified ASP phase behavior is often used. A state-of-the-art geochemical package, IPhreeqc, of the United States Geological Survey was coupled with UTCHEM, an in-house research chemical-flooding reservoir simulator developed at The University of Texas at Austin (UT), for a robust, flexible, and accurate integrated tool to mechanistically model ASP floods. UTCHEM has a comprehensive three-phase (water, oil, microemulsion) flash package for the mixture of surfactant and soap as a function of salinity, temperature, and cosolvent concentration. Through this integrated tool, we are able to simulate homogeneous and heterogeneous (mineral dissolution/precipitation), irreversible, surface complexation, and ion exchange reactions under nonisothermal, nonisobaric, and both local-equilibrium and kinetic conditions. Italic words are defined in Appendix A. IPhreeqc has rich databases of chemical species and also the flexibility to include the alkaline reactions required for modeling ASP floods. Hence, to the best of our knowledge, for the first time, the important aspects of ASP flooding are considered. An algorithm is presented for modeling the geochemistry in an implicit-in-pressure-and-explicit-in-concentration solution algorithm. Finally, we show how to apply the integrated tool, UTCHEM-IPhreeqc, to match three different reaction-related chemical-flooding processes: ASP flooding in an acidic active crude oil, ASP flooding in a nonacidic crude oil, and alkaline/cosolvent/polymer flooding.