Saline stable polymers

He did see considerable promise for polymers of HEC type and the biopolymers xanthan and scleroglucan were also found to be quite acceptable. However, Akstinat did not present very detailed stability results for the polymers in his study. Also, note that in the work of Akstinat, and in the work of Davison and Mentzer (1980), the objective was to find stable polymers for high-salinity brines (in the latter case based on sea water from the North Sea). It is well known, and it is discussed in detail below, that polyacrylamides are severely restricted in their performance in hard brines (i.e. brines containing divalent ions Ca ", Mg " ) (Zaitoun and Poitie, 1983 Moradi-Araghi and Doe, 1984). 

The replacement of PBS, or a 0.9% saline solution,by mannitol or sorbitol, of the same osmolarity as is the physiological solution, in order to minimize the charge screening of the polymer complex represents another possible direction to increase the strength of the complex. Matthew et al. [17] have applied a mannitol solution for the encapsulation of hepatocytes, showing that the mixture of CMC and chondroitin sulfate C formed a stable complex with chitosan in the absence of salts. 

Another system similar to the microbaU is called inverse polymer emulsion. In this case, the polymer used is polyacrylamide (PAM). The inverse PAM emulsion is a W/O type of emulsion. The dispersed phase contains 6.4 to 10.5 million Daltons PAM and 1000 mg/L crosslinkers for a sample product. The external continuous phase is white oil. There is a surfactant interfacial film between the disperse phase and continuous phase, as shown in Figure 5.16. The emulsion is stable at the surface. When it is injected into a target formation, it is inverted into an 0/W type of emulsion under certain temperature and salinity, with the help of a phase inversion agent. Thus, the name inverse emulsion is used. 

Dilute aqueous polymeric emulsions are commonly stabilized through the use of polymeric surfactants. If the stabilizer is uncharged, the emulsion is stabilized entropieally by segmental exclusion. In most instances, however, stabilization is a by product of coulombic repulsions generated by a polyelectrolyte surfactant. In a few instances the polymer itself is able to act as surfactant. For example, Eudragit RL, a commercially available partially quaternized cationic methacrylate based polymer, is able to form indefinitely stable emulsions in distilled water or buffered saline (141). These emulsions are prepared by adding polymer to boiling solution and are presumably stabilized by concentration of cationic functionality at the particle surface. 

White, hygroscopic, amorphous polymer. Soluble in water up to 10%. pH of 1% saline soln 5-9. Stable in soln and when autoclaved. Polymers with mol wt of 5000-10,000 have LDh i.v. in mice of 25-40 mg/kg. Ref Kimura et at., Toxicol Appl. Pharmacol. 1, 185 (1959), therap cat Heparin antagonist. 

The chemical industry then was confronted with the task of developing a polymer that remained stable in high salinities over a longer period, and at temperatures up to approx. 220 °F (105 °C). 

Polyvinylpyrrolidone (PVP) (monomer-unit structure [I]) is a water-soluble synthetic polymer v ich is stable physically and ch ically in aqueous solution (1-3), and which is commercially available in a diversity of molecular weight grades (4). From these features alone, PVP has potential for use in oil-recovery and related applications similarly, its monomer unit has potential as a component of copolymers tailored for these applications (5). In any such applications, it is important not only that the polymer remains in solution under all conditions of teirperature, pressure and salinity that may be encountered, but that its solutions also retain the desired rheological behavior. Ensuring that this happens, especially with novel copolymers, requires that we have a good understandirq of the molecular interactions which occur in these aqueous polymer systems. 

Brines Used in Frannie Study. Four different brines were used during the laboratory evaluation of polysaccharide and polyacrylamide polymers for the Tensleep reservoir. Frannie injection brine (FIB) was nearly identical in composition to the low-salinity, highhardness reservoir interstitial water. Because FIB was unstable in air owing to the presence of H2S, a chloride-based Frannie injection brine (CBFIB) was formulated as a stable substitute for FIB. Field Madison brine (FMB) was a stable, low-salinity alternative to FIB. Chloride-based enriched Madison brine (CBEMB) was simply FMB saturated with calcium sulfate to simulate the brine that... 

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