Pusher viscosities

For this study flow (dynamic) and static (batch) tests were carried out on Wilmington oil field unconsolidated sands at reservoir temperatures and flow rates with polyacrylamide (Dow Pusher-500) polymers. Effluent concentration, viscosity, and pH were monitored as a function of time. Extensive characterization studies for the sand were also carried out. 

The values for xanthan gum were also reported in an earlier work (7). The molecular sizes were obtained by using the Flory relation (8). There are alternate discussions as to what the configuration and the size of xanthan gum molecules in solution are. Whitcomb, Ek, and Macosko have presented an interpretation of the intrinsic viscosity data assuming a cylindrical rod conformation (9). The K-j and a values for Pusher are given by Lynch and Mac-Williams (10). It should be noted that a range of Kj and a values for polyacrylamides can be found in the literature (11). 

Polyacrylamides are extremely sensitive to shear fields as pointed out in the literature (13,14) Any orifice mixing breaks up the chains of polyacrylamides. The viscosities of Pusher solutions are plotted against the number of cycles through an orifice in Figure 6. Even with a 1/16" orifice (which has less than a 10 psi pressure drop across it), the viscosity drops from 14.1 cp to 10.9 cp showing more sensitivity than the other polymers. Agitation with a propeller at low speeds (less than 500-600 rpm) is a proper mixing mode for polyacrylamides. 

Pusher -700 and xanthan gum have larger molecular sizes in solution than Colloid and hydroxy ethyl cellulose. The dimensions in solution decrease with increasing salt concentration. Polyacrylamides are affected most severely by the presence of electrolytes. Polysaccharides are also affected by salt, but not to the same extent as polyacrylamides. Hydroxy ethyl cellulose is the most insensitive polymer to salt. Temprature can be inversely correlated with viscosity. Polyacrylamides have low activation energies for viscous flow. In order of decreasing temperature dependency are xanthan gum, Colloid , and hydroxy ethyl cellulose. 

Oil displacement experiments were performed under different salinity conditions (1) constant salinity of pol3nner solution at 1.5% NaCl (i.e. optimal salinity of the soluble oil formulation), and variable connate water salinity (2) constant salinity of connate water at 1.5% NaCl and variable salinity of pol3mier solution and (3) the salinity of polymer solution equals the salinity of connate water, both varied simultaneously. Sand packs were chosen as the model porous media in order to avoid the effects of porous media heterogeneity, clays and surfactant adsorption loss. The compositions of aqueous formulation and soluble oils are specified in Figures 1 and 2. The difference between their compositions reflects the density difference between water and dodecane whereas the surfactant and alcohol concentrations (w/v) are the same in both types of formulations. The polymer solution used was 1000 ppm PUSHER-700 in brine. For polymer solution in distilled water, the polymer concentration was reduced to 250 ppm to avoid excessive viscosity. Several experiments were repeated and the reproducibility was established to be within 2% in tertiary oil recovery. 

Shupe examined the effect of anionic surfactants (petroleum sulfonate) on the viscosity of partially hydrolyzed polyacrylamide (Dow Pusher 500) [69], The viscosity decreased by 22% as a result of adding the surfactant at 3 wt%. Nasr-El-Din et al. examined the influence of Neodol 25-3S on the viscosity of Alcoflood 1175L [41], Figure 19 depicts the flow curves of 1,000 ppm polymer solutions obtained at various surfactant concentrations (up to 10wt%). Unlike the results obtained with Triton X-100, Neodol 25-3S had a dramatic effect on the flow curves of the polymer solutions. This effect is similar to that obtained with simple salts. 

NajSjO 50 ppm HPAM-Dow Pusher 700 700 ppm Fresh water 50°C 9-9.1 Knight (1973) Viscosity of HPAM constant over 33 days. Loss of screen factor only 4%. About 30% loss of SF seen without Na2S204 in 47 days... 

Tetraethylene pentamine (TEPA) 500 ppm HPAM-Dow Pusher 700 900 ppm Nj purge to get 1-1.3 ppm O2 24 C Deionised water 96-100°C Glass et ai (1983) No HPAM viscosity losses observed over 100 days—severe loss of viscosity in the absence of TEPA... 

TABLE 5.2—SOLUTION VISCOSITY FOR 1,500-ppm PUSHER 500 IN 53 meofL NaCI AT 72.3°F, EXAMPLES. ... 

When an electrolyte, such as NaCl, is added to a polymer solution, the repulsive forces are screened by a double layer of electrolytes and extension is reduced. As the electrolyte concentration increases, the extension of the polymer chain decreases and the solution viscosity declines. Fig. 5.1533 illustrates the effect of salinity on the relative viscosity (apparent solution viscosity/solvent viscosity) of 250-ppm solutions of Pusher 700 , a partially hydrolyzed polyacrylamide.34 Chain extension also is controll by the... 

Fig. 5.15—Variation In relative viscosity with salinity and shear rate for 250-ppm Pusher 700 solutions at 25°C, (Reprinted with permission from the Canadian Inst, of Mining, Metallurgy, and Petroleum.)...

Fig. 5.54—Water and estimated Pusher 700 relative permeabilities when effective polymer viscosities are used during displacement of polymer by oil (Sample Berea-4).

The polymer used in the Vernon pilot exhibits the property of unusually high resistance to flow through porous media. " A small concentration in injected water effects a mobility reduction considerably beyond that predicted from increases in bulk viscosity as measured in a capillary or rotating cup viscosimeter. Water mobility in the subject flood is reduced by a factor of 7.55 with the addition of 500 ppm Pusher chemical to... 

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