CO2-Foam Rheology Behavior Under Reservoir Conditions

Abstract

Abstract Super critical carbon dioxide (SC-CO2) flooding is one of the most important enhanced oil recovery (EOR) methods used for conformance control and deep diversion of SC-CO2. It minimizes gravity override of SC-CO2 bypassing oil in the lower part of the formation. This paper investigates the impact of various parameters such as liquid/liquid ratio, different foam qualities and different injection modes on the SC-CO2-foam quality and its rheological properties. SC-CO2 foam can control the SC-CO2 mobility, enhance the sweep efficiency in reservoirs and improve the conformance control. Experimental results shows that combining foam with supercritical and dense CO2 will reduce the mobility of SC-CO2 to oil and water, stabilize the SC-CO2 injection front and mitigate the gravity override to a great extent resulting in less amount of unwept oil and better displacement efficiency and more recovery gain. Different set of lab experiments designed and conducted to identify the right ratio that can drastically increase SC-CO2 viscosity. In this work, we explored the rheological properties of SC-CO2 foam/gel chemicals with different pressure and temperature. Two different types of surfactants were tested. The experimental setup and conditions were designed to allow surfactant to mix with SC-CO2 under high reservoir pressure and temperature (HPHT) to create foam to evaluate and screen the foam quality and texture. The rheological properties of the SC-CO2-foam were investigated by varying the shear rate, shear stress, foam quality, injection modes and foaming agent concentrations at reservoir conditions. The effects of foam quality and liquid/liquid ratio, pressure and temperature on SC-CO2-foam at synthetic brine-environment rheology behavior, stability and mobility of foam were investigated. The foam study experiments were conducted using different scenarios: once by injecting SC-CO2 and surfactant solutions simultaneously and another time by alternate injection of CO2/surfactant solution at different flow rates at different foam qualities. The experimental results have shown that the foam mobility (total mobility of CO2 /surfactant solution) decreased with increasing foam quality ranging from 20% to 80%. The rheological properties of N2-foam were investigated and compared with SC-CO2-foam properties. This was correlated with the images of the high pressure, high temperature (HPHT) foams that were captured through microscope at different time intervals and analyzed to indicate their stability.