A Systematic Study of Alkali Surfactant Gas Injection as an Enhanced Oil Recovery Technique
- Mayank Srivastava (U. of Texas at Austin) | Jieyuan Zhang (University of Texas) | Quoc Phuc Nguyen (U. of Texas at Austin) | Gary A. Pope (The University of Texas at Austin)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 4-7 October, New Orleans, Louisiana
- Publication Date
- Document Type
- Conference Paper
- 2009. Society of Petroleum Engineers
- 4.3.1 Hydrates, 5.5 Reservoir Simulation, 1.8 Formation Damage, 5.4.2 Gas Injection Methods, 4.3.4 Scale, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 1.2.3 Rock properties, 5.4 Enhanced Recovery, 5.4.1 Waterflooding, 5.2.1 Phase Behavior and PVT Measurements, 5.2 Reservoir Fluid Dynamics, 4.1.5 Processing Equipment, 2.5.2 Fracturing Materials (Fluids, Proppant), 2.4.3 Sand/Solids Control, 7.4.5 Future of energy/oil and gas, 4.1.2 Separation and Treating, 5.3.2 Multiphase Flow, 2.2.2 Perforating, 1.6.9 Coring, Fishing
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Alkaline-Surfactant-Polymer (ASP) flooding is an attractive enhanced oil recovery method. However, some reservoir conditions are not favorable for the use of polymers or their use would not be economically attractive due to low permeability or other unfavorable conditions. Foam can be an alternative to polymer for improving the displacement efficiency in chemical-EOR process. The use of foam as a mobility control agent by co-injection or alternate injection of gas and chemical slug is termed, here, as Alkaline-Surfactant-Gas (ASG) Process. Foam reduces the relative permeability of the injected chemical slug that forms microemulsion at ultra-low oil-water interfacial tension (IFT) and generates sufficient viscous pressure gradient to drive the foamed chemical slug. The concept of ASG process as an enhanced oil recovery technique is relatively new, with very little experimental and theoretical work available on the subject. Polymer is replaced by foam in corefloods experiments as a mobility control agent. Phase behavior and ASG coreflood experiments were carried out to identify high performance chemicals, designed for both foaming and strong IFT reduction performance. The coreflood experiments were performed on sandstone and dolomite rock samples. Oil recovery and coreflood pressure response were evaluated to determine the success of the process. Different injection strategies for foam generation were investigated, and mechanisms of mobility control by foam were studied. Several promising surfactants, with dual properties of foaming and emulsification, were identified and used in the coreflood experiments. Maximum recovery of 95% of remaining oil after waterflood was observed. Oil recovery and pressure responses from ASG experiments are comparable to ASP coreflood experiments carried out under similar conditions. Experimental data show a strong synergic effect of foam and ultra-low oil-water IFT on oil recovery. Compared to polymer, foam has lower cost associated with its use and is less susceptible to biological, shear, and thermal degradation. The use of foam in chemical EOR can reduce the technical disadvantages associated with polymer in low permeability and fractured reservoirs.
Polymer is widely used for mobility control in enhanced oil recovery (EOR) processes. In Alkaline-Surfactant-Polymer (ASP) process, polymer provides mobility control during ASP slug and polymer drive injection. However, there are several disadvantages of using polymer. Some of the major disadvantages are:
- High molecular weight polymers can plug rocks with very low permeability, or if a lower molecular weight polymer is used to avoid plugging, then the cost of using
polymer increases and eventually becomes uneconomic.
- Many of the commercially available EOR polymers can be unstable at high temperature.
- Some polymers can mechanically degrade due to high shear stress through chokes or perforations at high flow rate.
- There can be other problems with polymers under some conditions associated with unfavorable interactions with surfactants.
|File Size||1 MB||Number of Pages||15|