Use of Mixed Surfactants To Generate Foams for Mobility Control in Chemical Flooding
- F.M. Llave (Natl. Inst. for Petroleum and Energy Research) | D.K. Olsen (Natl. Inst. for Petroleum and Energy Research)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- May 1994
- Document Type
- Journal Paper
- 125 - 132
- 1994. Society of Petroleum Engineers
- 5.4.6 Thermal Methods, 5.4.2 Gas Injection Methods, 5.4.1 Waterflooding, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.4 Enhanced Recovery, 1.6.9 Coring, Fishing, 5.3.4 Reduction of Residual Oil Saturation, 5.7.2 Recovery Factors, 5.3.2 Multiphase Flow, 2.5.2 Fracturing Materials (Fluids, Proppant)
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The potential application of mixed surfactant foams as a mobility-controlagent behind a low-concentration chemical flood was evaluated by laboratoryexperiments. A beneficial synergistic effect by improving the foam generationbehavior and stability of the formulation resulted in the propagation of a foamfront through porous media that contributed to a significant reduction inmobility and porous media that contributed to a significant reduction inmobility and increase in oil recovery. This enhanced oil recovery (EOR) processinvolves the injection of alternate slugs (or simultaneous injection) of gasand surfactant solution as drive fluids behind an active surfactant slug frontas an alternative to the use of polymers to eliminate unfavorablesurfactant-polymer interactions.
Experiments showed that using alternate slug cycles of 0.10 PV of mixedsurfactant formulations as foaming a gents and 0.10 PV of nitrogen gas resultedin significant differential pressures (as much as 27 times higher) across acore. The differential pressures generated by injecting mixed surfactantformulation and nitrogen gas were significantly greater than when using the(individual) component commercial surfactants and gas alone, even atconcentrations less than 0.1 wt % active surfactant. The mixed surfactantformulations were stable in the presence of oil, exhibiting comparable orbetter stability than the foams generated using the individual surfactants.Results indicate that the addition of another surfactant such as an amine oxideto an anionic foaming system has a positive synergistic effect by improving thefoam generation behavior of the formulation. Steady-state experiments wereconducted to determine the effect of foam flow rate on mobility reduction, andcoreflood oil displacement experiments were performed to compare variousinjection modes and oil recovery efficiencies. Results showed that thegeneration and propagation of a foam front behind a low-concentrationsurfactant slug propagation of a foam front behind a low-concentrationsurfactant slug contributed to a significant increase in oil recovery.
Surfactant-enhanced waterflooding has been widely researched for enhancedoil recovery (EOR). Principally, the surfactant slug is injected to lower theinterfacial tension between the water and oil. Lowering the interfacial tensionresults in more efficient oil displacement and a significant reduction in theoil saturation. The active surfactant slug is then pushed by a drive fluid,which is typically water. Problems that hinder the efficiency of this processstem from the Problems that hinder the efficiency of this process stem from theunfavorable mobility of the slug and the drive fluid with respect to the targetoil. Such unfavorable conditions result in the bypassing, dilution, andbreakdown of the surfactant slug. To offset such problems, methods for mobilitycontrol of surfactant slugs have received increasing attention from theresearch community. Proposed methods in the literature include the use ofpolymer-thickened water as the drive fluid. Foams have been used for EORapplications primarily for their potential in improving oil recovery as well asmobility control. Bernard and Holm patented the use of foams to reduce CO2mobility. They observed that gas permeability in the presence of foam was muchless than in the absence of foam when both were measured at the same gassaturations. More studies on using foams for mobility control have also beendirected towards their use in steamflooding and solvent flooding and ininjection of CO2 or other gases.
An evaluation of the application of mixed surfactant systems to generatestable foam for mobility control in surfactant flooding is presented. Thisprocess involves the injection of alternate slugs of presented. This processinvolves the injection of alternate slugs of gas and mixed surfactant solutionas drive fluids behind the selected active surfactant slug. The idea behindthis mobility control method is to generate foam to provide a reduction inmobility of the surfactant slug. The potential improvement in oil recovery fromthis process comes from two factors: (1) mobility control enhancement resultingin improved volumetric sweep efficiency; and (2) improved displacementefficiency from the contribution of the active surfactant slug and thesurfactant component of the foam. The use of a surfactant-based mobilitycontrol method eliminates some of the problems associated with typical polymertreatment methods. These problems include undesirable polymer-surfactantinteraction and polymer precipitation, limited penetration, loss of injectivityand polymer precipitation, limited penetration, loss of injectivity and loss ofviscosity caused by shear degradation.
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