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

Abstract

Abstract 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 due to the complicated ASP phase behavior and the complexity of geochemical reactions that occur in the reservoir. Due to 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. UTCHEM-IPhreeqc, a previously developed robust, accurate, and flexible integrated tool at the University of Texas at Austin (UT), is further expanded to mechanistically model ASP floods. UTCHEM has a comprehensive three-phase (water, oil, microemulsion) phase behavior model for the mixture of surfactant and soap as a function of salinity, temperature, and co-solvent concentration. IPhreeqc, a state-of-the-art geochemical package of the United States Geological Survey (USGS), handles the geochemical reactions involved between crude oil, rock, and brine. Through this integrated tool, we are able to simulate homogeneous and heterogeneous (mineral dissolution/precipitation), irreversible, surface complexation, and ion-exchange reactions under non-isothermal, non-isobaric, and both local-equilibrium and kinetic conditions. IPhreeqc has rich databases of chemical species and also the flexibility to define the alkali reactions required for the ASP modeling. Hence, to the best of our knowledge, for the first time, the important aspects of ASP flooding are considered. The expanded integrated tool, UTCHEM-IPhreeqc, is then used to match three different reaction-related chemical flooding processes: ASP flooding in an acidic active crude oil, ASP flooding in a non-acidic crude oil, and alkaline/co-solvent/polymer (ACP) flooding.