A Laboratory Study of Clay Stabilizers
Authors: Coulter A.W. , Copeland C.T. , Harrisberger W.H. 
Published: December 2007

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Introduction

Clay migration and the permeability damage it causes are recognized as serious problems in petroleum production. Only a few systems exist that can production. Only a few systems exist that can control this problem permanently. As reported in the literature, these systems are quaternary ammonium chlorides and inorganic polynuclear cations: specifically zirconium and aluminum. Their use generally has been limited to consolidated formations. Only Reed and Coppel have conducted research with unconsolidated formations. Apparently, this is because of the difficulty of performing valid laboratory flow tests on loose, clayey performing valid laboratory flow tests on loose, clayey formation sand. Special equipment has been designed that allows us to maintain an even stress field on unconsolidated clayey sand during flow tests. This prevents channeling or fingering of the fluid through the sand pack and assures uniform fluid penetration. Previous attempts to flow acid through such cores shocked the clays, causing migration and permeability loss. Also, the acid fluids either fingered through or blocked completely. Current data are much more reproducible and more nearly representative of unconsolidated formation treatments. Carrier fluids and preflushes now can be tested with reasonable assurance of obtaining meaningful data. New findings on the influence of such fluids on performance of clay stabilizers are reported here.

Special Apparatus

For this study, flow and water sensitivity tests were performed to measure clay stabilizer efficiency. performed to measure clay stabilizer efficiency. These tests were conducted using a test cell specifically designed to provide an evenly stressed, symmetrical pack of unconsolidated sand. This special cell, referred to as a piston-loaded test (PLT) cell, consists of a cylinder in which the unconsolidated sand is compacted between two pressure-driven pistons (Fig. 1). The length of the pressure-driven pistons (Fig. 1). The length of the sand pack is maintained at less than the sum of the diameters of the pistons. Here, the piston diameter was 2 in. (5.1 cm), making it necessary for the sand packs to be less than 4 in. (10.2 cm) long. This packs to be less than 4 in. (10.2 cm) long. This length-to-diameter ratio was maintained to avoid arching of the sand to the walls of the cell. Forming a bridge or an arch of sand particles transfers a vertical force to a horizontal force. This allows areas beyond such an arch to escape the confining stress. Such arching creates an uneven stress field in the pack, with resulting variations in particle loading and porosity. Arching is prevented by keeping the cell length less than two diameters. Actual sand-pack lengths varied from 2.2 to 2.5 in. (5.6 to 6.4 cm).

Test Procedures

Formation materials were treated with a clay stabilizer using one of the following two procedures. In Procedure 1, the specified amount of the clay stabilizer under evaluation was mixed with 1.25 PV carrier fluid (assuming 30% porosity).

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