Evaluation of Cyclic Steam Injection with Carbon Dioxide Enhanced Oil Recovery from Extra Heavy Oil Reservoir

No more than 5% of extra heavy oil is recovered economically through natural depletion with long horizontal wells in Venezuela Orinoco Heavy Oil Belt, manifesting a significant potential for Enhanced oil recovery (EOR). For the shallow extra heavy oil reservoirs, the ability to form the foamy oil flow is week, the cold production considering the low initial formation pressure and GOR is lower than expected, the implementation of EOR should be the new production strategies. In this study, experimental studies were carried out to measure the phase behavior and physical properties of oil saturated with CO2 under different pressure and temperature. The viscosity of oil with gas solution is tested in laboratory study. The evaluation of cyclic steam injection with Carbon Dioxide scenarios is based on the numerical simulation models. This study demonstrates that this technology has potential to implement in the shallow extra heavy oil reservoirs with certain oil flow capacity and formation energy is not enough and oil is viscous. The oil viscosity is sensitive to the temperature based on the results of viscosity-temperature experiment. The gas injected can extend swept volume and help steam distribute more uniformly along the horizontal sector, CO2 dissolved in the oil can help reduce the oil viscosity, especially in the lower temperature zone. The solubility of the CO2 is higher with the increasing pressure, and the effect of the viscosity reduction is more obvious. CO2 and steam injected mainly focus on the near wellbore in the early stage. The injected gas and steam combining with the crude oil can be assumed to form the foamy oil flow. The ratio of steam to CO2 should be no more than 1:1.5 to have better performance on oil recovery based on the optimization results. This paper presents the evaluation of the cyclic steam injection with CO2 to improve the oil recovery in extra heavy oil reservoirs, provides new strategies for effective development in shallow extra heavy oil reservoirs.