Foam in porous media

The WAG process has been used extensively in the field, particularly in supercritical CO2 injection, with considerable success (22,157,158). However, a method to further reduce the viscosity of injected gas or supercritical fluid is desired. One means of increasing the viscosity of CO2 is through the use of supercritical C02-soluble polymers and other additives (159). The use of surfactants to form low mobihty foams or supercritical CO2 dispersions within the formation has received more attention (160—162). Foam has also been used to reduce mobihty of hydrocarbon gases and nitrogen. The behavior of foam in porous media has been the subject of extensive study (4). X-ray computerized tomographic analysis of core floods indicate that addition of 500 ppm of an alcohol ethoxyglycerylsulfonate increased volumetric sweep efficiency substantially over that obtained in a WAG process (156). 

We can conclude that the stability of static foam in porous media depends on the medium permeability and wetting-phase saturation (i.e., through the capillary pressure) in addition to the surfactant formulation. More importantly, these effects can be quantified once the conjoining/disjoining pressure isotherm is known either experimentally (8) or theoretically (9). Our focus... 

Laboratory Apparatus for Study of the Flow of Foam In Porous Media Under Reservoir Conditions... 

The numerous previous studies of the flow of foam in porous media and of its application for. improving the displacement of oil from such media, have almost always been conducted under ambient conditions of temperature and pressure there have been very few reports of laboratory studies under reservoir conditions. Although many interfacial properties are known to be temperature dependant, little attention has been paid to the influence of temperature upon the properties of foam. Furthermore, the rheological properties of foams, and their effectiveness for the displacement of oil are strongly dependant upon foam quality, which is in turn... 

The stability of foams in constraining media, such as porous media, is much more complicated. Some combination of surface elasticity, surface viscosity and disjoining pressure is still needed, but the specific requirements for an effective foam in porous media remain elusive, partly because little relevant information is available and partly because what information there is appears to be somewhat conflicting. For example, both direct [304] and inverse [305] correlations have been found between surface elasticity and foam stability and performance in porous media. Overall, it is generally found that the effectiveness of foams in porous media is not reliably predicted based on bulk physical properties or on bulk foam measurements. Instead, it tends to be more useful to study the foaming properties in porous media at various laboratory scales micro-, meso-, and macro-scale. 

Among the many available defoamers, crude oil has been used to prevent the formation of foams, or destroy foams already generated, in a variety of industrial processes [43,46,327]. Crude oil can also destabilize foams applied in petroleum reservoirs, i.e., foams in porous media [3,306,328-331] (see Section 11.2.2). Although crude oils tend to act as defoamers, foams actually exhibit a wide range of sensitivities to the presence of oils, and some foams are very resistant to oil [3,332,333]. Many system variables influence the oil tolerance of a given foam and many attempts have been made to correlate foam-oil sensitivity with physical parameters [307,332-337]. These have met with mixed success [114,338],... 

Any foam for which the length scale of the confining space is greater than the length scale of the foam bubbles. The converse case categorizes some foams in porous media, distinguished by the term lamellar foam . See also Foam, Foam Texture. 

Raterman, K.T. An Investigation of Oil Destabilization of Nitrogen Foams in Porous Media in Proceedings, 64th. Ann. Tech. Conference, Society of Petroleum Engineers Richardson, TX, 1989, paper SPE 19692. 

Kristiansen, T.S. Holt, T. Properties of Flowing Foam in Porous Media Contaiing Oil in Proc., 12th International Workshop and Symposium, IEA Collaborative Project on EOR, Atomic Energy Agency Winfrith, UK, 1991. 

EOR process requires a detail study not only of foam behaviour in porous media but also of the options to control it. Foam flow in porous media during EOR is a complex, multifaceted process. A number of papers are dedicated to that topic, including some reviews [e.g. 13,14,18] which describe the experimental set-up used in the study of foams in porous media. We will focus on those illustrating the efficiency of EOR from oil pools and the role of some important factors, involving the effect of foam properties, especially of the critical capillary pressure. 

The effect of stability of single foam films as gauged by the magnitude of tear disjoining pressure on the flow resistance of a foam in porous media has been investigated by... 

Surfactant Foam in Porous Media Topical report SUPRI TR-48 U.S. Department of Energy, Washington DC, October, 1985. 

FLUMERFELT PRIEDITIS Mobility of Foam in Porous Media... 

As mentioned before. Equations (5) and (6) are the differential transport equations of average bubbles and could be written from scratch without the convoluted derivations invoked here. Unfortunately, modeling of foam flow in porous media is a lot more complicated than Equations (3) and (6) lead us to believe. Having started from a general bubble population balance, we discovered that flow of foams in porous media is governed by Equations (2) and (3), and that Equations (5) and (6) are but the first terms in an infinite series that approximates solutions of (2) and (3). 

The continuum form of the bubble population balance, applicable to flow of foams in porous media, can be obtained by volume averaging. Bubble generation, coalescence, mobilization, trapping, condensation, and evaporation are accounted for in the volume averaged transport equations of the flowing and stationary foam texture. 

This completes the derivation of the continuum form of the population balance of bubble number density suitable for modeling the flow of foam in porous media. 

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