Dispersion-based flow control

The use of surfactants to create dispersions that improve flow behavior in EOR is currently associated quite closely with CO2 and with steam flooding. However, for two decades research on dispersion-based flow control focused on the development of low-pressure, low-temperature foams for other applications, such as improving water floods and reducing the losses of natural gas from underground storage. Direct applications to CO2 flooding did not appear until 1978 (48,49). 

Dispersion Formation, Subdivision, and Coalescence. The ability to create and control dispersions at distances far from the injection well will be critical to the field-use of dispersion-based mobility control. The early studies of Bernard and Holm, followed by more recent work by Hirasaki, Falls, and co-workers, and others showed that the flow properties of surfactant-induced dispersions depend on the presence and composition of oil, volume ratio of the dispersed and continuous phases, capillary pressure, and capillary number (35,37,39-41,52-54,68). However, it is the size of the droplets or bubbles that dominates dispersion flow (39,68). Moreover, early debates on the ratio of droplet (or bubble) size to pore size have been resolved by ample evidence showing that, under commonly employed conditions, droplets are larger than pores (39). Only for very large capillary numbers (i.e., for interfacial tensions of ca. 

More field tests will be needed, especially to incorporate research advances in such areas as materials design phase behavior and dispersion morphology mechanisms of dispersion formation, flow, and breakdown and simulation of dispersion-based sweep control. 

Mast, in a pioneering 1972 paper, reported visual observations of foam flow in etched glass micromodels (37 ) His observations showed that some of the conflicting claims about the properties of foam flow in porous media were probably due simply to the dominance of different mechanisms under the various conditions employed by the separate researchers (37). Mast observed most of the various mechanisms of dispersion formation, flow, and breakdown that are now believed to control the sweep control properties of surfactant-based mobility control (37,39-41). 

Chem. Descrip. POE-modified dimethylpolysiloxane block copolymer Uses Wetting agent, emulsifier in water-based coatings, inks, polishes, hard surf, cleaners clay/pigment dispersant leveling agent flow control... 

Uses Low-foaming dispersant for water-based coatings, slurries, adhesives, etc. visc./flow control agent best for water sensitivity Trade Names Busperse 2143 Troythix LLBA... 

Low Solids/Nondispersed. Fresh water, clay, and polymers for viscosity enhancement and filtration control make up low sohd/nondispersed muds. Low soflds muds are maintained using minimal amounts of clay and require removal of all but modest quantities of drill soflds. These are called nondispersed systems because no additives are used to further disperse or deflocculate the viscosity building clays. Most water-based muds are considered dispersed because deflocculating additives are used to control the flow properties. 

Okamoto et al. [48] first conducted an elongation test on PP-based nanocomposites in the molten state at constant Hencky strain rate, so using elongation flow optorheo-metry [49]. They also attempted to control the alignment of the dispersed silicate... 

The flow injection technique is based on three main principles sample injection, reproducible timing, and controlled dispersion [128]. The dispersion can be described as limited, medium, or large in a colorimetric system based on a reaction between the sample and a suitable reagent, a medium dispersion is preferred. Thus in the flow injection determination of nitrate, the reductor column should not excessively increase the dispersion. In a copperised cadmium reductor, more than 90% of the total nitrate is reduced within 1 - 2 s with minimum risk of further reduction of nitrite [167]. Consequently, the reductor can be made very small, which results in a minimal increase of dispersion. 

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