Microvisual and Coreflood Studies of Foam Interactions With a Light Crude Oil
- Laurier L. Schramm (Petroleum Recovery Inst.) | Alexandru T. Turta (Petroleum Recovery Inst.) | Jerry J. Novosad (Petroleum Recovery Inst.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- August 1993
- Document Type
- Journal Paper
- 201 - 206
- 1993. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 5.4 Enhanced Recovery, 4.1.2 Separation and Treating, 5.3.4 Reduction of Residual Oil Saturation, 4.3.4 Scale, 2.5.2 Fracturing Materials (Fluids, Proppant), 4.1.5 Processing Equipment, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.2 Reservoir Fluid Dynamics, 5.2.1 Phase Behavior and PVT Measurements
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Foam stability in the presence of crude oil is important to foamfloodperformance. Microvisual observations were made to assess the degree offoam-lametia/oil interactions occurring between a light crude oil and foamsbeing considered for foam flooding applications in Alta., Canada. Foambehaviors ranged from quite stable, with almost no foam/oil interactions, toquite unstable, where oil was extensively emulsified and imbibed into the foam.These behaviors matched phenomenological model predictions and also wereconsistent with coreflood mobility reduction factors and incremental oilrecoveries obtained in foam flow experiments in Berea sandstone cores atambient temperature, low pressure, and residual oil saturation (ROS).
In gasflood EOR methods, serious problems occur owing to the high mobilityof the displacement agent compared with that of reservoir fluids. Largemobility contrast is associated with severe channeling and possibly withgravity override, both of which can contribute to early breakthrough, reducedsweep efficiency, and reduced oil recovery. Foam, which has an apparentviscosity greater than the displacing medium, can lower gas mobility in theswept and high-permeability parts of the formation and could alleviate theseproblems. Foam use has increased recently in field applications. Although manylaboratory investigations of foam flooding have been carried out in the absenceof oil, the effect of the oil saturation is crucial for an oilfieldapplication. The foam may encounter oil in a reservoir when applied either as aslug followed by a displacement agent or as a continuous injection. Oils arewellknown agents for foam inhibition and breaking and can have a destabilizingeffect on EOR foams. Also, some foams are more stable than others in thepresence of oil. This work addresses foam stability in the presence of crudeoil. Several foam/oil interaction mechanisms based on surface energy conceptshave been proposed and subsequently observed in microvisual experiments withnumerous foams and a medium crude oil. The mechanism of foam collapse in thepresence of oil apparently involves emulsification of oil into foam lamellae,which allows the drops to move inside the foam structure and have adestabilizing effect consistent with the entering mechanism of foam breaking.The foam stability observed in the microvisual cell correlated with the lamellanumber, which expresses a driving force for emulsification. The present studiesalso include a second, lighter crude oil. Coreflood studies of foam performancealso have been conducted under oil-free and residual oil conditions, butcomparison of the results is difficult. The parameters, experimentalprocedures, surfactants, and oils used by different investigators toprocedures, surfactants, and oils used by different investigators to measurefoam efficiency vary considerably. The literature, however, shows that foamscan reduce gas mobility in porous media but tend to be sensitive to thepresence of residual oil. Foam mobility reduction factors in sandstone cores atwaterflood ROS may be 10 to 30 times lower than those in oil-free cores evenwhen relatively high PV's (10 to 100) of foam are injected. Althoughqualitative comparisons have been made, there has not been a systematiccomparison of coreflood results, microvisual studies, and basic physicalproperties; this is the second objective of this study.
Phenomenological Theory Phenomenological Theory A previous study suggestedthat emulsification and imbibition must take place before oil can destroy foamsby spreading or entering.
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