Importance of a Second Liquid Phase Formation in CO2 Injection into Bitumen Reservoirs and its Effect on Production

Abstract

The injection of different solvents, such as propane and CO 2 , into bitumen, has proven to be an effective method in the production of these kinds of reservoirs. However, in some cases, the prediction of large solvent requirements can make it uneconomical. The formation of a second liquid phase has been observed when the solvent is propane or CO 2 , with the second liquid phase mainly composed of the solvent itself. The objective of this research is to understand the importance of this second liquid phase and its effect on production. Also, a simulator that can allocate an individual phase to this liquid phase would allow for prediction of the amount of solvent that can be produced and recycled. This makes the cost evaluation of solvent injection processes to be more realistic. Depending on the reservoir fluid distribution, a three-or four-phase flow can occur in the absence or presence of water. A compositional simulator based on an equation of state is designed to simulate these multiphase situations. This simulator has a four-phase flash and stability subroutine, which make it more realistc compared to other compositional simulators. In fact, it can handle a maximum of three hydrocarbon phases and one aqueous phase. Relative permeability plays an important role in multiphase flow; numerical results indicate that, by increasing the number of phases, there is an increase in project life. It is valuable to mention that the results of this research can be also used in CO 2 sequestration.

Phase Behavior of a United Arab Emirates Stock-Tank Oil and Carbon Dioxide at Reservoir Conditions: Experiments and Thermodynamic Modeling

“…The formation of a second liquid phase when propane or CO 2 was used as solvent was observed by Feizabadi et al [11]; claiming that the second liquid phase is mainly composed of the solvent itself.…”

“…Feizabadi et al [11] observed the formation of a second liquid phase when propane or CO 2 , was used as solvent, with the second liquid phase mainly composed of the solvent itself. They carried out a research to understand the importance of the second liquid phase and its effect on oil production.…”

Determination of Three-Phase Boundaries of Solvent(s)–CO2–Heavy Oil Systems under Reservoir Conditions

“…Recent studies prove that adding alkane solvent C 3 H 8 into the CO 2 stream is able to significantly improve the recovery performance of CO 2 flooding in heavy oil formations. , Such improvement is achieved on the basis of several important mechanisms, which mainly encompass the enhanced swelling effect and viscosity reduction of heavy oil, and interfacial tension (IFT) reduction between the gas mixture and heavy oil. In addition to these established mechanisms, it is possible that the observed three-phase L 1 L 2 V equilibria of the solvent(s)–CO 2 –heavy oil systems may also play an important role in improving the heavy oil recovery performance of solvent-enriched CO 2 flooding processes. , …”

“…In addition to these established mechanisms, it is possible that the observed three-phase L 1 L 2 V equilibria of the solvent(s)− CO 2 −heavy oil systems may also play an important role in improving the heavy oil recovery performance of solventenriched CO 2 flooding processes. 13,14 …”

“…On the other hand, one possible benefit arising from the emergence of the L 2 phase is that the L 2 phase reduces the gas-phase saturation in the pores. A reduction in gas saturation suppresses the gas-phase relative permeability, delaying the gas breakthrough, and results in a better sweeping efficiency . Nevertheless, it is possible that the existence of the L 2 phase also leads to a lower gas injectivity because of the suppressed gas-phase relative permeability.…”