Ecology, Environment and Conservation Paper

OIL PRODUCTION, GRAVITY DRAINAGE MECHANISM

Isemin A. Isemin and Francis D. Udoh

Abstract

Gravity drainage is a recovery mechanism for a fractured reservoir that consists of matrix and fractures. The entire process of this gravity drainage is dependent on the density difference between the oil in the matrix and the gas in the fracture thereby providing the pressure difference required for the oil recovery from the matrix block. Several equations to quantify flow through matrix and fracture have been provided by many authors. An analytical model is described to determine the time at which gas enters into pores to displace oil in the matrix block based on water displacement. Eclipse 100 reservoir simulator is used in the computer simulation to study how oil is produced by gravity drainage mechanism in fractured reservoirs. The simulation is performed on a single block and stack of blocks. The effect of fracture aperture, matrix permeability, capillary continuity between matrix block, and block height on oil recovery is considered. Fracture aperture contributed to recovery only for a single block, and regardless of where the injection well or production well was placed, it did not affect recovery. Recovery rate under gravity drainage was ob-served to be in the range of 1% to 7%.