Aqueous-phase saturation profiles

Figure 12. Experimental and model transient aqueous-phase saturation profiles. Model results are shown with solid lines. Experimental data points (symbols) are connected by dashed lines.

Solution of the coupled mass-transport and reaction problem for arbitrary chemical kinetic rate laws is possible only by numerical methods. The problem is greatly simplified by decoupling the time dependence of mass-transport from that of chemical kinetics the mass-transport solutions rapidly relax to a pseudo steady state in view of the small dimensions of the system (19). The gas-phase diffusion problem may be solved parametrically in terms of the net flux into the drop. In the case of first-order or pseudo-first-order chemical kinetics an analytical solution to the problem of coupled aqueous-phase diffusion and reaction is available (19). These solutions, together with the interfacial boundary condition, specify the concentration profile of the reagent gas. In turn the extent of departure of the reaction rate from that corresponding to saturation may be determined. Finally criteria have been developed (17,19) by which it may be ascertained whether or not there is appreciable (e.g., 10%) limitation to the rate of reaction as a consequence of the finite rate of mass transport. These criteria are listed in Table 1. 

The relative mobility of the aqueous phase in the region contacted by polymer is the relative mobility of the polymer flowing in the rock. Because and X, are functions of the saturation profile and fluid properties, when the saturation profile is known, as in Fig. 5.66, the mobilities of both phases can be computed at every value of X. Eq. 5.122 can be integrated to find the pressure drop corresponding to the value of tj). Thus... 

Mechanistic interpretations The results of the dynamic and equilibrium displacement experiments are used to evaluate and further define mechanisms by which alkaline floods increase the displacement and recovery of acidic oil in secondary mode and the tertiary mode floods. The data sets used in the mechanistic interpretations of alkaline floods are (a) overall and incremental recovery efficiencies from dynamic and equilibrium displacement experiments, (b) production and effluent concentration profiles from dynamic displacement experiments, (c) capillary pressure as a function of saturation curves and conditions of wettability from equilibrium displacement experiments, (d) interfacial tension reduction and contact angle alteration after contact of aqueous alkali with acidic oil and, (e) emulsion type, stability, size and mode of formation. These data sets are used to interpret the results of the partially scaled dynamic experiments in terms of two-stage phase alteration mechanisms of emulsification followed by entrapment, entrainment, degrees and states of wettability alteration or coalescence. 

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