Reservoir waterflooding-E. Fig. P1.7(a) shows how water is pumped down one well, of depth H, into an oil-bearing stratum, so that the displaced oil then flows up through another well. Fig. P1.7(b) shows an enlargement of an idealized pore, of diameter d, at the water/oil interface. Water in Oil Po out Impermeable rock Well Well Water H Oil Oil-bearing stratum Pore (enlarged) (a) (b) Fig. P1.7 Waterflooding of an oil reservoir. If the water and oil are just starting to move, what water inlet pressure p, is needed if the oil exit pressure is to be p,? Assume that the oil completely wets the pore (not always the case), that the water/oil interfacial tension is a, and that the densities of the water and oil are Po, respectively. 10 Pw and