Microstructure and Formula Optimization of Co2 Flooding Composite Gel in Supercritical Carbon Dioxide

Injection of CO2 into low permeability reservoirs tend to both enhance the oil recovery effectively and reduce the CO2 emissions. However, the reservoir heterogeneity, reservoir cracks and viscous fingering lead to CO2 channeling occuring during the process of CO2 flooding. Four parameters (CO2 pressure, simulation temperature, reaction time, and concentrations of reactants) were optimized through L16(44) orthogonal experiment, and the most appropriate conditions for inorganic gel were also acquired simultaneously as follows: reaction pressure 9.0 MPa, reaction temperature 32.01, reaction time 14.0 h, and sodium silicate mass concentration 4.0%. The compound gel was synthesized by the method of blending sodium silicate solution with an acrylamide system in supercritical CO2. The microstructure of the compound gel was researched through environmental scanning electron microscopy (ESEM), and the results showed that, in supercritical CO2, the inorganic gel particle equaly dispersed in the organic gel network inside the structure, thus the support framework of the organic polymer chain was formed and the strength of the compound gel was finally enhanced.