The Performance of Bottom Water-drive Reservoirs

Abstract

Abstract A theory has been developed describing the behavior of wells and reservoirs producing by the action of bottom Water drives. It is assumed that the pressures are maintained above the bubble point, and that the permeability to viscosity ratio of the water in the flooded zone is the same as for the oil in the oil saturated pay. Accordingly, the treatment is based on the homogeneous fluid potential theory. The effect of the difference in density between the oil and water is neglected. After deriving the proper potential distributions, the nature of the rise of the water-oil interface below the producing wells is calculated. The primary clean-oil-production phase is expressed in terms of the displacement efficiency, defined as the fraction of the pay flooded out by the rising water table at the lime of first water entry. The variation of this displacement efficiency is calculated as a function of the well spacing, pay thickness, the ratio of the horizontal to vertical permeability, and the well penetration. The important parameter other than the well penetration is found to be the ratio of the well separation to the thickness of the oil pay multiplied by th~ square root of the ratio of vertical to horizontal permeability. It was found that the displacement efficiency continually decreases as this parameter increases. and' for values of the latter > 3.5, the efficiency varies inversely as the square of the parameter. It also increases with decreasing well penetrati