Dynamic growth of water saturation around oil wells by water coning and transverse dispersion

Abstract

Reported is a study of permeability damage around a well with water coning problem—after water breakthrough, when the stratified inflow of oil (top) and water (bottom) generates a dynamic transition zone. The enlarged transition zone distributes a water saturation barrier that reduces oil inflow to the well. Using high-resolution reservoir simulator with small grid blocks around the well, we qualified the effects of viscous force, gravity and capillary pressure, and postulated an additional effect resulting from high velocity flow around the well—transverse dispersion (i.e. hydrodynamic mixing). The effect contributes additional growth of the transition zone. Normally, in commercial simulators, the extra transition zone due to transverse dispersion would be neglected as it is overshadowed by capillary pressure when the flow velocity is low. However, it becomes progressive in the well's vicinity since the transverse dispersion coefficient is a function of velocity. We postulate in the paper that the transverse dispersion effect should be added to the well inflow model. The proposed analytical mechanistic model employs coefficient of transverse dispersion as a function of fluid and rock properties. It is shown that well productivity could be significantly affected by water invasion due to transition zone enlargement caused by transverse dispersion. It is also shown that by diverting the stream of water with Downhole Water Sink completion the spontaneous growth of transition zone could be controlled.