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.

Experimental Investigation and Modeling of Naphthenate Soap Precipitation Kinetics in Petroleum Reservoirs

“…However, particle jamming at the pore throats is more likely to occur because the area open for flow is small and the particles are more likely to coalesce when approaching the pore-throat constrictions. The present study confirms "porethroat plugging" as being the possible formation damage mechanism according to Wojtanowicz et al 8 and Civan 9 .…”

“…Wojtanowicz et al 8 showed that the damage mechanism is controlled by the size of the particles. Therefore, the particle size experiments were conducted by taking snapshots of naphthenate soap particles under a light microscope at 200X magnification at different times.…”

“…Several core flow tests were carried out to observe the permeability impairment with respect to time and verify that pore throat plugging is the mechanism responsible for formation damage. The Wojtanowicz et al 8 diagnostic equations were employed to identify the type of formation damage.…”

A Novel Workflow to Model Permeability Impairment through Particle Movement and Deposition in Porous Media

“…A quantitative model for the process of formation permeability alteration due to particle invasion and in-situ fine mobilization, using the principles of deep bed filtration and chemical reaction kinetics, has been proposed by Wojtanowicz et al (1988). Three mechanisms of formation pore blocking have been recognized and analyzed in this model with regard to particles invasion, which are gradual pore blocking, single pore blocking (screening), and cake formation (straining).…”

“…There are six reported modeling studies concerning the in-situ generation and migration of fines in porous media (Gruesbeck and Collins 1982;Khilar and Fogler 1987;Soo and Radke Clayton 1986;Wojtanowicz et al 1988;Civan et al 1990;Rochon et al 1996). In each of these studies simplified assumptions are made and the equations are solved to describe the reduction in permeability due to migration of the fine particles in porous media.…”