Drive fluids

Miscible processes are aimed at recovering oil which would normally be left behind as residual oil, by using a displacing fluid which actually mixes with the oil. Because the miscible drive fluid is usually more mobile than oil, it tends to bypass the oil giving rise to a low macroscopic sweep efficiency. The method is therefore best suited to high dip reservoirs. Typical miscible drive fluids include hydrocarbon solvents, hydrocarbon gases, carbon dioxide and nitrogen. 

The flow distribution in a manifold is highly dependent on the Reynolds number. Figure 14b shows the flow distribution curves for different Reynolds number cases in a manifold. When the Reynolds number is increased, the flow rates in the channels near the entrance, ie, channel no. 1—4, decrease. Those near the end of the dividing header, ie, channel no. 6—8, increase. This is because high inlet velocity tends to drive fluid toward the end of the dividing header, ie, inertia effect. 

Variable drive fluid couplings (see Section 8.4.1(2)) These may not prove to be as effective from the point of view of energy conservation, as the motor will always be running at its rated speed and engagement of the coupling alone will vary the output speed. 

In arterioles, the hydrostatic pressure is about 37 mm Hg, with an interstitial (tissue) pressure of 1 mm Hg opposing it. The osmotic pressure (oncotic pressure) exerted by the plasma proteins is approximately 25 mm Hg. Thus, a net outward force of about 11 mm Hg drives fluid out into the interstitial spaces. In venules, the hydrostatic pressure is about 17 mm Hg, with the oncotic and interstitial pressures as described above thus, a net force of about 9 mm Hg attracts water back into the circulation. The above pressures are often referred to as the Starling forces. If the concentration of plasma proteins is markedly diminished (eg, due to severe protein malnutrition), fluid is not attracted back into the intravascular compartment and accumulates in the extravascular tissue spaces, a condition known as edema. Edema has many causes protein deficiency is one of them. 

A solids-stabilized water-in-oil emulsion may be used either as a drive fluid for displacing hydrocarbons from the formation or to produce a barrier for diverting the flow of fluids in the formation. The solid particles may be formation solid particles or nonformation solid particles, obtained from outside the formation (e.g., clays, quartz, feldspar, gypsum, coal dust, asphaltenes, polymers) [228,229]. 

Oil recovery can also be affected by extreme variations in rock permeability, such as when high-permeability thief zones between injectors and producers allow most of the injected drive fluid to channel quickly to producers, leaving oil in other zones relatively unrecovered. A need exists for a low-cost fluid that can be injected into such thief zones (from either injectors or producers) to reduce fluid mobility, thus diverting pressure energy into displacing oil from adjacent lower-permeability zones. 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

Enhanced oil recovery The process in which a foam is made to flow through an underground reservoir. The foam, which can either be generated on the surface and injected or generated in situ, is used to increase the drive fluid viscosity and improve its sweep efficiency. 

After approximately 2 min, apply suction with a mbber tube connected to the narrow arm of the viscometer, drawing the reaction mixture above the upper mark into the driving fluid head. Measure the efflux time by allowing the reaction mixture to freely flow down past the upper mark. As the meniscus of the reaction mixture falls past the upper mark, start stopwatch no. 2. At the same time, record the reaction time, in minutes, from stopwatch no. 1 (Tt ). As the meniscus of the reaction mixture falls past the lower mark, record the time, in seconds, from stopwatch no. 2 (Tt). 

In recent years there has been considerable interest in the use of foams in chemical steam flood, CO2, and low tension processes. To date, principal applications have been as diverting agents where the foam has been used to block high permeability, low oil saturation zones and hence force drive fluids through lower permeability, higher oil saturation zones. The utility of foams in more general mobility control roles has not been extensively... 

In older plants which used a reciprocating compressor for the recycle, a recycle cylinder was often mounted together with the other cylinders on the reciprocating frame. Sometimes special rotary compressors, so-called mole pumps were also used, with the unique feature that compressor and electric driver were completely enclosed in a common high-pressure shell. In old Casale plants, the makeup gas was introduced into the high pressure recycle loop and acted as the driving fluid of an injector which compressed the recycle gas. 

Shan J, Liao J, Huang J et al (2012) Bicarbonate-dependent chloride transport drives fluid secretion by the human airway epithelial cell line Calu-3. J Physiol 590(Pt 21) 5273-5297... 

Chemical methods of EOR are usually carried out by using water or brine as the carrier fluid. The exception is foam flooding, which also involves an immiscible gas as the driving fluid. Although various chemical methods can be used by themselves, studies have shown synergism in their combined application. 

---