Polymer reservoirs

The sensors are constructed from Plexiglass cubes that have been drilled to accommodate a 600 /im optical fiber, polymer, and to provide a pathway for the analyte (Figure 2). The physical dimensions of the sensor are 15 mm by 12 mm by 10 mm. The volumes of the polymer reservoir and the reaction chamber are 100 /il and 40 jil, respectively. The lyophilized immunoreagents are incorporated into EVA at 1.5% (dryweight) for fluorescein-labeled anti-IgG antibody (F-Ab) and 8.0% Texas Red-labeled IgG (TR-Ag). Pieces of the polymers are then packed in the polymer reservoirs. 

Figure 2. Immunosensor Configuration. Reagent is released from the polymer reservoirs into the reaction chamber where a competition reaction takes place with analyte diffusing in from the bulk solution.

The second system was developed by the Hereon Division of Health Chem Corporation and consists of a laminated plastic chip. Figure 2. The chip is composed of a pheromone saturated polymer reservoir with a semi-permeable plastic membrane on either side. The pheromone is thus released by diffusion from the reservoir through the membrane. The rate is controlled by the membrane composition and thickness(2,). The two systems are applied in a polybutene sticker to facilitate adhesion to the plant surface. 

Figure 13.12 Density autocorrelation functions f q, t) (probed at the same scattering vector). The dynamics is probed at a scattering vector corresponding to the peak maximum of the structure factor of the pure colloid suspension at its glass-transition volume fraction. The polymer reservoir volume fractions cj) are indicated by the numbers at the curves. The thick solid lines correspond to nonergodic (glassy) samples. (Reprinted with permission from Eckert T. and Bartsch E. Re-entrant glass transition in a colloid-polymer mixture with depletion attractions Phys. Rev. Lett, 89 125701, 2002. Copyright 2002 by the American Physical Society.)...

Figure C2.3.11 Key surfactant stmctures (not to scale) in emulsion polymerization micelles containing monomer and oligomer, growing polymer particle stabilized by surfactant and an emulsion droplet of monomer (reservoir) also coated with surfactant. Adapted from figure 4-1 in [67],...

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36). 

Polymer Flooding. Even in the absence of fractures and thief 2ones, the volumetric sweep efficiency of injected fluids can be quite low. The poor volumetric sweep efficiency exhibited in waterfloods is related to the mobiUty ratio, Af, the mobiUty of the injected water in the highly flooded (low oil saturation) rock, divided by the mobiUty of the oil in oil-bearing portions of the reservoir, (72,73). The mobiUty ratio is related to the rock permeabihty to oil, and injected water, and to the viscosity of these fluids by the following equation ... 

Eig. 3. This polymer flooding method requites a preflush to condition the reservoir, the injection of a polymer solution for mobihty control to niinimi2e... 

Excessive hydrolysis of polyacrylamide in situ can promote undesirable polymer precipitation in the reservoir. The rate of this hydrolysis decreases with increasing level of anionic comonomers such as AMPS (130). 

By 1980, research and development shifted from relatively inexpensive surfactants such as petroleum sulfonates to more cosdy but more effective surfactants tailored to reservoir and cmde oil properties. Critical surfactant issues are performance in saline injection waters, adsorption on reservoir rock, partitioning into reservoir cmde oil, chemical stabiUty in the reservoir, interactions with the mobiUty control polymer, and production problems caused by resultant emulsions. Reservoir heterogeneity can also greatly reduce process effectiveness. The decline in oil prices in the early 1980s halted much of the work because of the relatively high cost of micellar processes. 

Piston Cylinder (Extrusion). Pressure-driven piston cylinder capillary viscometers, ie, extmsion rheometers (Fig. 25), are used primarily to measure the melt viscosity of polymers and other viscous materials (21,47,49,50). A reservoir is connected to a capillary tube, and molten polymer or another material is extmded through the capillary by means of a piston to which a constant force is appHed. Viscosity can be determined from the volumetric flow rate and the pressure drop along the capillary. The basic method and test conditions for a number of thermoplastics are described in ASTM D1238. Melt viscoelasticity can influence the results (160). 

Amoco developed polybutene olefin sulfonate for EOR (174). Exxon utilized a synthetic alcohol alkoxysulfate surfactant in a 104,000 ppm high brine Loudon, Illinois micellar polymer small field pilot test which was technically quite successful (175). This surfactant was selected because oil reservoirs have brine salinities varying from 0 to 200,000 ppm at temperatures between 10 and 100°C. Petroleum sulfonate apphcabdity is limited to about 70,000 ppm salinity reservoirs, even with the use of more soluble cosurfactants, unless an effective low salinity preflush is feasible. 

A second field evaluation of the ASP process has been initiated in Wyoming. Additionally, an ASP field project has been designed for the Peoples Repubhc of China. The appHcability of the ASP process to a variety of reservoirs has yet to be fully determined. AppHcation of alkali and alkali polymer flooding has been limited to cmde oils having discernible acid numbers, wherein the alkali produced cmde oil soaps which in combination with alkali resulted in providing low interfacial tensions. The ASP process appears to be suitable for cmde oils with nil acid numbers (177), and hence should have broad apphcabdity. 

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