Suresh Kumar Govindarajan

Effect of Gravity: Does high API gravity oil remain more suitable for the CO2 miscible flooding process compared to lower gravity oils? Yes, high API gravity oil is generally more suitable for CO2 miscible flooding. High API gravity indicates lighter oil with lower viscosity, which allows better mobility of CO2 through the reservoir. This is essential for achieving good miscibility between CO2 and oil, as CO2 must be able to move effectively through the reservoir and dissolve in the oil. Lower gravity oils typically have higher viscosity, which makes CO2 migration more challenging and can lead to poor miscibility. Does lower oil gravity mean higher viscosity, leading to an unfavorable mobility ratio and poor sweep efficiency due to viscous fingering? Yes, lower oil gravity generally means higher viscosity. Higher viscosity leads to an unfavorable mobility ratio between CO2 and oil, which can cause viscous fingering. Viscous fingering occurs when the more viscous fluid (high viscosity oil) cannot be efficiently displaced by the lower viscosity fluid (CO2), resulting in poor sweep efficiency and reduced recovery. Effect of Viscosity:Do reservoirs with oil viscosities lower than 12 cp remain more appropriate for CO2 miscible flooding? Yes, reservoirs with oil viscosities lower than 12 cp are generally more appropriate for CO2 miscible flooding. Lower viscosity allows better mobility of CO2 through the reservoir, improving the efficiency of miscible flooding. Oils with viscosities below 12 cp typically allow CO2 to flow more easily, reducing the risk of viscous fingering and improving sweep efficiency. Remaining Oil in the Reservoir:If the remaining oil in the reservoir is less than 300 STB/acre-ft, will CO2 miscible flooding still succeed? CO2 miscible flooding can still be successful, but its efficiency will depend on the amount of remaining oil, the type of reservoir, and other factors. If the remaining oil is below 300 STB/acre-ft, the reservoir is already partially depleted, but CO2 can still help recover the remaining oil. However, in such cases, the potential for CO2 to improve recovery may be reduced compared to reservoirs with larger amounts of remaining oil. Reservoir Permeability:If the reservoir permeability is less than 5 md, will CO2 miscible flooding still succeed? CO2 miscible flooding may face challenges if the reservoir permeability is less than 5 md. Low permeability limits the flow of CO2 through the reservoir. While CO2 can still be effective in low-permeability reservoirs, its mobility will be restricted, which could reduce the efficiency of the flooding process. In such reservoirs, CO2 may have difficulty distributing evenly, which affects the overall recovery process. Enhanced CO2 Mobility vs. Water-Flooding:Although CO2 injection through the development of miscibility has the potential to increase recovery, could the ‘enhanced CO2 mobility’ and ‘increased CO2 phase segregation’ reduce the total recovery factor (RF) compared to water-flooding? Yes, enhanced CO2 mobility and increased phase segregation could reduce the total recovery factor (RF) compared to water-flooding. While CO2 injection has the potential to improve recovery, excessive CO2 mobility can lead to uneven distribution and bypassing of oil zones, resulting in lower recovery efficiency. Increased CO2 phase segregation could cause CO2 to exit the miscible phase before it contacts all parts of the reservoir, reducing the overall recovery. On the other hand, water-flooding tends to have a more stable and uniform flow, making it more efficient in certain reservoirs with lower mobility. While CO2 miscible flooding has significant potential to increase recovery, its success depends on factors such as oil viscosity, reservoir permeability, remaining oil, and CO2 mobility. Proper management of these factors is essential to optimize recovery and achieve successful enhanced oil recovery (EOR) through CO2 flooding.