An Acrylic/Epoxy Emulsion Gel System For Formation Plugging: Laboratory Development And Field Testing For Steam Thief Zone Plugging
Authors: Knapp R.H. , Welbourn M.E. 
Published: December 2007

A new delayed gelation fluid for formation plugging applications in profile control for plugging applications in profile control for injection wells and for water shutoff in producers has been developed and field tested. This gel is formed by the cross-linking chemical reaction between an acrylic resin and a liquid epoxy resin contained in a water continuous phase emulsion. The resin droplets in the emulsion are about 1 micron or less in size so that the emulsion freely flows into typical formations.

The acrylic/epoxy gel has several features that offer advantages over previous polymer gel systems. These features include the following.The gel time for this plugging fluid is not sensitive to oxygen saturation.The characteristics of the gel obtained are not degraded by sheening the fluid prior to gelation.The mixing formulation is simple and can be easily adjusted for gel time control over a wide temperature range.The ambient temperature gel time is extremely long, e.g., 30 days.The initial viscosity of the fluid is low.The gel obtained is a tough, rubbery acrylic/epoxy plastic material.The gel adheres to silica so that unconsolidated sand becomes a plastic-like material with some compressive strength.The gel has useful temperature stability to about 300 degrees F.

This paper discusses the chemistry and laboratory development of this gel plugging system. Also reported are results of the initial three field tests of the system for plugging steam thief zones. Thief zones were plugged successfully in each of these wells. The success of these treatments was evidenced by higher steam injection pressures, higher oil production, and elimination of communication to production, and elimination of communication to offset wells. The steps necessary to mix and pump this gel plugging system in the field are covered.

Introduction

A fundamental problem of any flooding or injection process for oil recovery is the injection well profile control problem. The injected fluid can only recover oil effectively when it flows into a productive oil zones. Loss of the injected fluid to productive oil zones. Loss of the injected fluid to nonproductive "thief zones" results in wasted injection fluid, as well as inefficient oil recovery. Similarly, unwanted water production (or other drive fluid) from a producer can limit the oil production capacity of a well and also incur the additional costs associated with lifting, separating, and treating this fluid.

Fig. 1 illustrates the profile control problem for injection wells. Also shown in Fig. 1 is the possibility of the drive fluid breaking through at possibility of the drive fluid breaking through at the producer. In order to attack the profile control problems illustrated in Fig. 1, several in-depth problems illustrated in Fig. 1, several in-depth plugging gels have been developed. For instance, the plugging gels have been developed. For instance, the successful use of a cross-linked polyacrylamide system in nonfractured injectors has been reported. Another type of polymer plugging system is the noncross-linked gel formed by the polymerization of acrylamide monomer. Also, dilute solutions (e.g., 2,000 ppm) of polyacrylamides have been used for treating producers to reduce water production.

This paper presents the chemistry and laboratory development of a polymer gel plugging system referred to as ACRYLEPON* that is based on the chemical cross-linking reaction between emulsified acrylic and epoxy resins. Several features of the ACRYLEPON gel give it advantages over previous polymer system. One of these features is that the polymer system. One of these features is that the gel time obtained with this plugging fluid is not sensitive to oxygen saturation. This is in contrast to the polyacrylamide systems. Also, the characteristics of the ACRYLEPON gel are not degraded by shearing the fluid prior to gelation, unlike the case of solutions of polyacrylamide.