Foam crude oils defoamers

Defoamers are used in oil extraction, such as in drilling muds and cementation, and also directly with crude oil itself. In its natural state, a crude oil contains dissolved gases at the pressure of the reservoir. When the pressure is reduced, the gases are liberated and troublesome foam can develop. There are three ways to prevent foaming in gas-oil separation ... 

Understanding the factors that inhibit the foaming power is of great importance, because it yields a basic knowledge— how the materials produced will perform with respect to foaming. It also serves to predict how individual crude oil compositions would work with different defoamers [301]. 

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],... 

Because the interfacial tension can change with time after an initial spreading of oil, 5 may be time-dependent, and it follows that, in some cases, oils may act as defoamers only for a limited amount of time. The dynamic interfacial tensions were studied (37, 40, 47) for various crude oil and foam-forming surfactant solution combinations. Some of these systems exhibited dynamic interfacial tensions, but typical variations over up... 

Results from field testing have suggested that foams may achieve lower gas mobility reductions than anticipated because of the defoaming action of residual crude oil [120], which has led to an interest in the formulation of oil-tolerant foams. Although crude oils tend to act as defoamers, it turns out that foams actually exhibit a wide range of sensitivities to the presence of crude oils, as discussed in Section 5.6.7. Overall, it is clearly possible to make foams... 

Surfactants are of great importance as auxiliaries for the production and processing of crude oil and gas (emulsifiers, agents for foaming and defoaming, lubricants, bactericides, corrosion inhibitors, de-emulsifiers, etc.). In particular, tertiary oil production represents a broad field for such applications. 

A stable foam possesses both a high surface dilatational viscosity and elasticity (21). In principle, defoamers should reduce these properties. Ideally a spread duplex film, one thick enough to have two definite surfaces enclosing a bulk phase, should eliminate dilatational effects because the surface tension of an insoluble, one-component layer does not depend on its thickness. This effect has been verified (22). Silicone antifoams reduce both the surface dilatational elasticity and viscosity of crude oils as illustrated in Table 2. The PDMS materials are Dow Coming Ltd. polydimethylsiloxane fluids, SK 3556 is a Th. Goldschmidt Ltd. silicone oil, and FC 740 is a 3M Co. Ltd. fluorocarbon profoaming surfactant. 

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