PRINCIPLES OF 3-PHASE CAPILLARY PRESSURES

In porous media, there are a variety of configurations in which three immiscible fluids can be distributed within a single body. For example , the fluids may be distributed as concentric rings. Alternatively, tw o fluids may be dispersed as separate blobs within the third fluid. Th e configuration governs the mobility of each fluid, and under equilibr ium conditions is dictated by the three phase capillary pressure of th e system. If the capillary pressure is altered, the configuration will change. Capillary pressure can be altered by flow of any phase throug h the pore body. However, in a three phase system flow cannot be descr ibed as simply ''drainage'' or ''imbibition.'' Rather, flow must be de scribed as ''drainage/drainage,'' ''drainage/imbibition'' or ''imbibit ion/imbibition'' to account for the change in saturation of all three phases. This paper elaborates on the issues governing three phase capi llary pressures and presents some first experimental results on oil/wa ter/gas capillary pressures in a drainage/drainage mode.