American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Spontaneous emulsification at liquid-liquid interfaces and Haines' jump phenomenon at liquid-gas interfaces may be explained in terms of classical fluid mechanics, mass and energy diffusion and surface thermodynamics. These phenomena are examined in this paper in terns of an interaction between Marangoni effects and capillary forces. Marangoni effects refer to the motion of an interface due to gradients in interfacial tension. The porous medium used to study these effects is described geometrically as an interconnected network of converging-diverging channels. The flow of two immiscible fluids in these channels is described by the Navier-Stokes equations at very low Reynolds numbers. Differences in the potential (temperature and/or concentration) of potential (temperature and/or concentration) of these fluid phases will induce mechanical movement of the interface. The resultant unsteady motion is modelled as a classical Rayleigh flow or suddenly accelerated plane flow. This motion will initiate disruption plane flow. This motion will initiate disruption of the interface if the pressure drop due to shear forces is greater than the pressure drop due to normal forces. Analytical expressions developed in this work suggest parametric dependence of interfacial unstabilities in porous media on (i) differences in the kinematic and absolute viscosity (ii) the magnitude and direction of the interfacial tension gradient due to temperature and/or concentration differences (iii) absolute magnitude of the interfacial tension (iv) wettability of the porous matrix and (v) a geometric factor which is porous matrix and (v) a geometric factor which is characteristic of the microscopic structure of the porous medium. The influence of these parameters is supported by experimental data from the parameters is supported by experimental data from the literature. Introduction Additional chemical and/or thermal energy is required to overcome the capillary forces which entrap large quantities of residual oil in depleted petroleum reservoirs. Removal or reduction of interfacial forces with or without the reduction of viscous forces will allow the mobilization of isolated droplets and ganglias of oil and the subsequent formation of local regions of high oil saturation. The reservoir mechanics of tertiary floods will thus have to consider a microscopic mobilization efficiency in addition to the macroscopic displacement and areal sweep efficiencies. Physical and mathematical conceptions of the isolation and mobilization mechanisms will be necessary for the quantifying of microscopic efficiencies.