ABSTRACT
In the southern coast of the Gulf of Mexico some deep geothermal aquifers are associated with hydrocarbon reservoirs. Some of their wells are invaded by geothermal brine, producing a variable mixture of hot water and oil. This water, at temperatures of 150◦C and having a density of 1150 kg/m3, flows vertically through a fault in the aquifer located at a depth of 6000 m. The non-isothermal conditions affect the effective saturations and the relative permeabilities of the immiscible phases. The relative permeability of oil is increased by the increase of temperature produced by the geothermal water. This effect reduces the residual saturation of heavy oils. At the same time, the dynamic viscosities of water and oil are diminished, affecting the displacement of both fluids. Although the oil is extracted inwells which end in the upper boundary of the aquifer, the total volume of produced water, in some cases, equals or exceeds the oil production. The handling of this extra hot water becomes a serious practical problem. We introduce a numerical original model able to predict the critical oil rate for which the wells can be totally invaded by geothermal brine.
