Profile control gels

Chromium(III) is a commonly-used crosslinker for preparing profile control gels with polymers having carboxylate and amide functionalities (la,b). Cr(III) is applied in many forms. For example, it can be used in the form of simple chromic salts of chloride and sulfate, or as complexed Cr(III) used in leather tanning (2), or as in situ generated Cr(III) from the redox reaction of dichromate and bisulfite or thiourea. The gelation rate and gel quality depend on which form of Cr(III) is used. 

The chromium(III) ion is a common crosslinker for preparing profile control gels for water flow control in oil reservoirs. This practical application of chromium chemistry has lead to two studies on the rate and mechanism of gel formation. A preliminary report using H NMR relaxation... 

Figure 8.8 Capillary gel electrophoresis profiles of collagen a-chains and chain polymers in 4% polyacrylamide after incubation for 4 days A) and 7 days (fl) at 30°C. Other conditions as in Figure 8.7. Note the splitting of peaks in the cr-region and the increase of y and higher chain polymers. Unincubated profile (control) is shown in Figure 8.7A. (From Deyl and MikSik, 1995, with permission.)...

Chemical flooding polymer, deep-formation profile control using gels, surfactant, alkaline, emulsion, foam, and their combinations... 

In the Xia-er-men field operated by Henan Oilfield, Sinopec, the produced water was used to make a polymer solution. Because of the high viscous oil and very heterogeneous reservoir, a normal polymer solution was not good enough to reach desired sweep efficiency. Profile control was tried instead. Because of small injection volume, however, water soon bypassed the injected gel. Therefore, a large volume of weak gel (deep profile control) was tested in a pilot. 

The injection volume of weak gel for profile control in H2II was larger than in the other two layers. 

Fig. 4. Nucleosome relaxation, and influence of histone N-terminal tails. Example of nucleosomes on 356 bp ALk= —2.9 topoisomer from the pBR DNA minicircle series [28]. (a) Mononucleosomes (Mo) were reconstituted with control (Control) or acetylated (Acetyl) histones, incubated at 37 °C in Tris buffer [T 50 mM Tris-HCl (pH 7.5), 0.1 mM EDTA, 50 mM KCl, 5 mM MgC, and 0.5 mM dithiothreitol] or phosphate buffer [P same as Tris buffer with 50 mM potassium phosphate (pH 7.5) instead of 50 mM Tris-HCl] in the absence (Topo I —) or presence (Topo I +) of topoisomerase I, and electrophoresed in a native polyacrylamide gel at room temperature. Note the splitting of nucleosome relaxation products in two bands. TE starting chromatin in TE buffer, (b) Gel slices (brackets) were cut out, and eluted DNAs were electrophoresed in a chloroquine-containing native polyacrylamide gel, together with control naked topoisomers (C1-C4). Lanes were numbered as in the (a) gel. Autoradiograms are shown, (c) Radioactivity profiles of lanes 2 and 5 in the (b) gel. Topoisomers are indicated by their ALk values. (Adapted from Fig. 2 in Ref. [28].)...

Fig. 3. Advanced protocol of 2D-DIGE for a number of protein samples larger than the available fluorescent dyes. The internal control sample and individual samples are labeled with CyS and CyS, respectively. The differently labeled protein samples are mixed together and separated on individual gels. After gel electrophoresis, the gels are scanned with laser at the appropriate wavelength for CyS and CyS. As all gel scans generate the CyS image that represents the proteomic profile of the internal control sample, gel-to-gel variations are compensated by normalizing CyS images with CyS images for each gel. We can compare more protein samples than the available fluorescent dyes.

At one extreme diffusivity may be so low that chemical reaction takes place only at suface active sites. In that case p is equal to the fraction of active sites on the surface of the catalyst. Such a polymer-supported phase transfer catalyst would have extremely low activity. At the other extreme when diffusion is much faster than chemical reaction p = 1. In that case the observed reaction rate equals the intrinsic reaction rate. Between the extremes a combination of intraparticle diffusion rates and intrinsic rates controls the observed reaction rates as shown in Fig. 2, which profiles the reactant concentration as a function of distance from the center of a spherical catalyst particle located at the right axis, When both diffusion and intrinsic reactivity control overall reaction rates, there is a gradient of reactant concentration from CAS at the surface, to a lower concentration at the center of the particle. The reactant is consumed as it diffuses into the particle. With diffusional limitations the active sites nearest the surface have the highest turnover numbers. The overall process of simultaneous diffusion and chemical reaction in a spherical particle has been described mathematically for the cases of ion exchange catalysis,63 65) and catalysis by enzymes immobilized in gels 66-67). Many experimental parameters influence the balance between intraparticle diffusional and intrinsic reactivity control of reaction rates with polymer-supported phase transfer catalysts, as shown in Fig. 1. 

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