The Experimental Study Of In-Situ Generated CO₂ Foam For Enhanced Oil Recovery

The experimental study of in-situ generated CO₂ foam for enhanced oil recovery was based on the injection of two aqueous solutions i.e.gas-forming and gas-yielding solutions of certain concentrations into the reservoir.In this research,in-situ CO₂ generated foam was obtained by an exothermic chemical reaction between gas forming Na₂CO₃ and low concentrated HCl.The advantage of this technology is that once the displacement agent is generated in-situ,it avoids any surface facility;eliminates CO₂ negative impact such as viscous fingering and gravity override problems and provides strong control of the process.Therefore,in-situ CO₂ generated flooding can effectively plug channeling between injection-production well,increase oil volume,decrease water cut and enlarge swept volume.Water-soluble foam generating surfactants were used during the experiments since they decrease interfacial tension in the oil-water contact once added to these solutions.Three anionic surfactants were tested using different surfactant concentrations,temperatures,salinity as well as determining the effect of the presence of crude oil and carbon dioxide gas on foam stability.This was determined by the half-life of the surfactants in which the longer the half-life,the better the foam stability.As the concentration of the surfactant increased,foam stability increased accordingly as shown by longer half-life exhibited by all the three surfactants.A surfactant with fairly stable foam when exposed to different conditions was chosen and used during coreflooding experiments.The results from the coreflooding experiments were used to optimize the injection quantity;injection method;further flooding rate;injection velocity;effect of injection continuity of CO₂foam generating agents and effect of injection stabilizer depending on which one gives optimum total oil recovery.It was noted that the more the quantity of the CO₂ foam generating agents injected,the more effective the reaction was and the better the blocking effect of the high permeability pores.On the number of slugs used,the higher the number of slugs,the more the total oil recovery.On the number of slugs used,the higher the number of slugs,the more the oil recovery hence to strike a balance with the economic aspects involved the interval of 6 to 10slugs can provide the best injection method for enhanced oil recovery.It was also observed that as the water injection rate increased during further waterflooding,there was no significant increase in the total oil recovery.During the visual flooding experiments,three processes i.e.bubble coalescence,bubble division and bubble deformation were observed under the microscope to determine the state of foam in porous media.As the pressure increased,bubbles in the foam became more dispersed.