Radial surfactant propagation

Figure 7. Example of radial surfactant propagation in a homogeneous reservoir.

Figure 7 shows how the measured adsorption levels translate into distance of surfactant propagation in a homogeneous reservoir with radial flow from the injector. A 40-acre five-spot pattern was assumed in calculating the pore volume (PV), and other assumptions are listed in the figure. The calculation of radial distance is based on a simple material balance using the following equation ... 

Figure 8 gives the radial distance that the surfactant can propagate in each layer when one pore volume of foam (0.1 PV of surfactant solution) is injected. An adsorption level of 0.2 mg/g or less is required for the surfactant to propagate all the way to the production well in the upper layer. 

Figure 6 indicates that many of the tested systems fulfill this requirement. Also, more than half of the surfactants in Figure 6 adsorb at less than 0.4 mg/g, and this adsorption results in a reasonable distance of propagation (200 m) in the high-permeability layer. The distances plotted in Figure 8 are conservative because flow in a reservoir that requires sweep improvement measures is not likely to be completely cylindrical but takes place through preferential flow channels. The calculations would also be more favorable for a linear (as opposed to radial) drive pattern. 

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