Experimental Determination of Formation Damage Pore Blocking Mechanisms

Abstract

The process of formation permeability damage due to solids movement and capture was quantitatively modeled by using principles of deep bed filtration and chemical reactions kinetics. The developed theory describes the pore blocking mechanism caused by particles from completion fluids (foreign particles invasion), as well as the mechanism of release and capture of rock fines (in-situ mobilization). For practical applications, this theory was used in the context of pattern recognition, i.e., to examine the experimental data on rock permeability change versus time from the laboratory flow experiments. Thus, a straight line section of data plotted in a certain system of coordinates indicated the type of formation damage occurring. The verification study was performed in two series of laboratory experiments. In the first, a completion fluid, contaminated with drilling mud, was pumped through the simulated synthetic rock. In the second, four typical, solids-free completion brines were pumped through actual samples of water-sensitive, unconsolidated sandstones taken from Adriatic Sea gas fields. The experiments revealed the applicability of the theory and the method of diagnostic plots to describe and analyze formation permeability damage.