ON INFLUENCE OF PHYSICAL AND CHEMICAL MODIFICATION OF WETTABILITY OF FILTRATION SURFACE ON INTERCHANGEABILITY OF IMMISCIBLE FLUIDS IN RESERVOIR FORMATIONS

Abstract

The article presents and discusses the results of experimental studies of the processes of mutual substitution (displacement) of immiscible fluids, proceeding by the mechanism of impregnation and drainage in layered-heterogeneous reservoirs with hydrodynamically connected and separated interlayers.
 Physical modeling of filtration processes, taking into account the similarity criteria, made it possible to establish that during the mutual substitution of immiscible fluids at the phase boundary and lithological differences, nonequilibrium capillary phenomena develop, which, through the action of capillary forces, significantly affect fluid filtration and saturation distribution in an inhomogeneous porous medium. In order to eliminate the influence of the viscous instability factor on the motion of the displacement front, the processes of displacement of a less viscous fluid by a more viscous one were studied.
 It has been established that non-equilibrium capillary phenomena manifest themselves most intensively in reservoirs with a heterophilic surface, where capillary forces can initiate or block fluid flows between differently permeable interlayers. It has been experimentally shown that in layered-heterogeneous reservoirs with a heterophilic filtration surface in the interlayers, capillary phenomena largely determine the nature of the movement of the fluid displacement front (from the almost complete suppression of the “run-up” of the displacement fronts in the interlayers to the formation of an advanced front in the low-permeability interlayer). In order to exclude the influence of errors of a systematic or random nature on the results of the experiments, their reproducibility and the significance of differences were assessed using the statistical criteria of Student and Cochran, which showed the reliability of the above conclusions.
 The results obtained indicate the dominant effect of crossflows between interlayers on the formation of the displacement front of immiscible fluids in layered-heterogeneous reservoirs, especially with a heterophilic wettability characteristic, as well as the possibility of controlling this process by means of physicochemical modification of the wettability conditions of the filtration surface, for example, using surface active substances (surfactants) of various nature and structure.