Importance of a Second Liquid Phase Formation in CO2 Injection into Bitumen Reservoirs and Its Effect on Production
- Seyed Ali Feizabadi (U Of Calgary) | Jalal Abedi (U. of Calgary) | Zhangxin John Chen (U. of Calgary)
- Document ID
- Society of Petroleum Engineers
- SPE Improved Oil Recovery Symposium, 14-18 April, Tulsa, Oklahoma, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.4 Enhanced Recovery, 5.3.2 Multiphase Flow, 5.4.6 Thermal Methods, 4.3.3 Aspaltenes, 5.2.2 Fluid Modeling, Equations of State, 5.5 Reservoir Simulation, 5.2.1 Phase Behavior and PVT Measurements, 4.1.9 Heavy Oil Upgrading, 1.8 Formation Damage, 2.4.3 Sand/Solids Control, 5.3.9 Steam Assisted Gravity Drainage, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.2 Reservoir Fluid Dynamics, 5.3.1 Flow in Porous Media, 1.2.3 Rock properties, 5.10.1 CO2 Capture and Sequestration, 5.4.2 Gas Injection Methods
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The injection of different solvents, such as propane and CO2, 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 CO2, 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 CO2 sequestration.
Heavy Oil and Bitumen
Heavy oil and bitumen are viscous mixtures of hydrocarbons and other organic compounds. In general, heavy oil and bitumen are classified according to API and viscosity. Crude oils with API less than 20º and viscosity less than 10,000 cp are known as heavy oils while those with viscosities greater than 10,000 cp are termed as extra heavy oil or bitumen (Das, 1995; Miller 1994).
Canada has huge heavy oil and bitumen resources. Original Oil In Place, OOIP is estimated to be more than 400 billion m3 (approximately 2.5 trillion bbl) which is approximately twice that of the total conventional oil reserves in the Middle East (Dusseault, 2001; Farouq Ali, 2003).
These reserves exist in unconsolidated sand and carbonate sedimentary formations of Athabasca, Cold Lake, Peace River and Wabasca regions in Alberta, Saskachewan and British Columbia. Heavy oil and bitumen are becoming more and more important considering the depletion of conventional oil reserves in the world. However, production of heavy oil and bitumen is more challenging and more expensive than that of conventional oils because of immobility of them in reservoir conditions due to their high viscosity.
There are two methods for recovery of heavy oil and bitumen: open pit mining by using large trucks and shovels and insitu recovery through wells. The first method is very effective (more than 90% recovery). However, this is only suitable for shallow reservoirs with overburden formation depth of less than 75m. In Canada, most of the reservoirs are deep enough not to be exploited by open pit mining.
At present time cold heavy oil production (CHOP), cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are the major in-situ recovery methods used in Canada.
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