The Flow of Viscous Polymer Solutions for Gravel Packing Through Porous Media

Abstract

ABSTRACT Gravel packing with viscous aqueous polymer solutions, as in Shell's Aquapac, often calls for fluid placement to the formation. To estimate placement pressures experiments have examined the flow of suitable polymer solutions through porous media ranging from coarse spherical beads to gravel pack gravel and simulated formation sand. The solutions are shown to follow power-law behavior, and pressure drops within the porous media can be described in terms of a simple power-law model. However, the solutions tend to form a gel at the inlet surface of the pack. The surface impairment may dominate the overall pressure drop particularly in the case of formation-like permeabilities. The surface buildup and potentially rapid viscosity breaking may effectively prevent meaningful predictions of pressure response. The results suggest that placement with these solutions may sometimes be very different than intended. Unanticipated high downhole viscosities may suggest interpretations involving "premature sandout." However, breakers can substantially reduce downhole viscosity during placement. Since the nature of gravel pack buildup is strongly dependent on solution viscosity, the detailed behavior may have an important influence on gravel pack effectiveness and productivity.