Understanding complex variation in dynamic characterizations of chemical solutions on the surface of rock related to different carbonate reservoir quality is one of the most challenging subjects in the enhanced oil recovery process because pore distribution, pore structure and petrophysical properties of carbonate reservoir have many differences. Carbonate reservoirs usually have heterogeneity, a wide range of pore levels and petrophysical parameters. This research aims to investigate systematically and explain the interrelationship between reservoir quality indexes (RQI) or flow zone indicator (FZI) and dynamic characterization of chemical solutions. The interrelationship derived can be applied to enhanced oil recovery in carbonate reservoirs.
Several laboratory studies were completed using carbonate core plugs and reservoir brine at reservoir conditions for dynamic characterization of chemical solutions for the potential application of enhanced oil recovery: 1). the evaluation of resistance factor (RF), residual resistance factor (RRF) and injectivity (I) of a sulfonated polymer; 2). dynamic adsorption and desorption of an amphoteric surfactant. The RQIs of carbonate core plugs are in the range of 0.74 to 1.91 µm.
Based on the results of this study, we found that the dynamic characterizations of chemical solutions depend on the RQI. The results from a sulfonated polymer solution injection tests show that RF and RRF increase with a decrease in RQI for both solutions of 0.1 wt% and 0.2 wt% polymer. However, there is a critical frontal velocity for such a polymer solution of 0.2 wt%. When the frontal velocity is more than critical frontal velocity, RRF has similar values with increase in front velocity. Liquid permeability loss at a concentration of 0.2 wt% is higher than that in the case of 0.1 wt%.
This paper provides a comprehensive overview of dynamic characterization of an amphoteric surfactant and sulfonated polymer for carbonate reservoir rocks with RQI and presents insights and large potential for application of chemically enhanced oil recovery in carbonate reservoirs.