A Gravel-Coating Aqueous Epoxy Emulsion System for Water-Based Consolidated Gravel Packing: Development and Application
Authors: Knapp Randolph H. , Planty Roger , Voiland Eugene J. 
Published: December 2007

This paper describes a water-based consolidated gravel-packing system for sand control that was developed and successfully field tested. The basis of the system is a catalyzed epoxy emulsion that coats gravel in the presence of water with internally catalyzed epoxy. presence of water with internally catalyzed epoxy. Introduction

The technique generally used to obtain sand control with a consolidated gravel-packing system is illustrated in Fig. 1. Gravel that has been sized properly to control the formation sand and that has a coating of a consolidating chemical (e.g., epoxy) is injected into the cased and perforated wellbore. Slurry injection is stopped so that perforated wellbore. Slurry injection is stopped so that gravel is screened out on the formation and packed in the wellbore, covering the perforations and filling them with consolidating gravel.

After this placement is accomplished, the well is shut in for a time to allow the gravel to consolidate. The final step in the process is to drill the consolidated gravel out of the wellbore and place the well on production.

Consolidated gravel-packing systems commonly in use at this time utilize an internally catalyzed epoxy that is mixed with the gravel and a viscous oil carrier. While these systems have been successful in some applications, they do not have the advantages that have been found with the current water-based gravel-packing systems. The advantages of water-based gravel-packing systems over systems in which the gravel is carried in oil include lower cost, easier field handling, less pollution hazard, better carrier fluid rheology, and possibly less impaired, more reliable gravel packs. Water-based consolidation systems conserve expensive and scarce hydrocarbons that are required with oil systems.

The previously reported water-based consolidated gravel-packing system uses a furan resin that is externally catalyzed by an acid overflush.

In order to overcome the limitations of previous systems, we have developed a water-based consolidated gravel-packing system, referred to as the AQUA-EPON* system, an internally-catalyzed epoxy system that is mixed and carried in water-based fluids.

The AQUA-EPON Process Surface and Emulsion Chemistry

The AQUA-EPON system uses an epoxy emulsion that is catalyzed by a relatively water-soluble amine having cationic surfactant activity. This surfactant activity causes the polymerizing epoxy to wet and coat strongly water-wet silica surfaces. In a water environment above pH 2.2, silica surfaces are negatively charged so that the pH 2.2, silica surfaces are negatively charged so that the positively charged catalyzed epoxy emulsion droplets are positively charged catalyzed epoxy emulsion droplets are attracted to the gravel surfaces. Fig. 2 shows a photo-electromicrograph of the grain-to-grain contacts of a photo-electromicrograph of the grain-to-grain contacts of a gravel bonded by the cured epoxy from the water-based epoxy emulsion system.

The dual function of the amine to catalyze the epoxy and cause it to wet silica surfaces is the result of the chemical equilibrium between the nonionized catalyst and the cationic amine. This equilibrium is controlled by emulsion pH so that control of the epoxy polymerization rate is possible by adjustment in emulsion pH.

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