This work establishes the flow mechanism of dilute, stable emulsions in fine grained porous media. Oil-in-water emulsions of mean drop sizes ranging from one to ten micrometers are studied in sandpacks of 0.57 and 1.15 mum² permeability at a superficial velocity of 0.07 millimeter per second. Low viscosity oil drops cause permeability reductions of up to 80 percent, with four to five micrometer size drops being the most effective. Examination of drop sizes and pore sizes, as well as transient effluent emulsion concentration and transient pressure data, reveals that permeability reductions during emulsion flow are caused by droplet capture mechanisms similar to those found for solid particle deep-bed filtration. The proposed filtration mechanism is verified by a micromodel study. -- AATA