Epoxy Sealant For Combating Well Corrosion
Authors: Cole Robert C. 
Published: December 2007

Current well completion techniques involve the use of higher strength, chemical and abrasion resistant pipe through subterreanean formations to control the injection or withdrawal of products from specific zones. The correct installation and maintenance of this pipe is essential for an efficient disposal or production program. This paper introduces an epoxy sealant-cementing system which possesses adhesion, compressive strength, and chemical resistance superior to portland and modified portland type cements. These superior properties provide the industry with a means of completing wells and repairing damaged pipe with the anticipation of long lasting results.

This epoxy system may be used to cement an entire casing string or part of a casing string in conjunction with more common portland type cements. This paper presents a detailed description of these procedures. Occasionally in both producing and procedures. Occasionally in both producing and disposal wells the installation of special alloy or fibercast liners is required to correct or prevent corrosion damage. Liner installation prevent corrosion damage. Liner installation procedures, using this epoxy system as the cementing procedures, using this epoxy system as the cementing medium, are also presented.

This paper introduces a new technique for repairing long sections of damaged or corroded pipe with this epoxy system without the use of a pipe with this epoxy system without the use of a liner.

Laboratory data comparing the properties of this epoxy system with other cementing materials and field data from wells treated according to the procedures outlined herein collectively demonstrate procedures outlined herein collectively demonstrate the advantages and applicability of this unique epoxy system.

Introduction

When wells are drilled into subterranean earthen formations, whether the purpose is to inject or to withdraw fluids, one requirement is paramount. The zone in question, communicating with the wellbore, must be isolated from other strata in the vicinity.

In wells where hydrocarbons are being produced, zone isolation is important because highly pressured zones containing unmarketable fluids such as water could choke off lower pressured zones of economic interest. Conversely, valuable hydrocarbons could unknowingly be forced into permeable low pressured strata if effective segregation is not employed. Also certain zones bearing naturally occurring corrosive fluids, such as water containing dissolved hydrogen sulfide gas or high salt concentrations, could communicate these harmful fluids to potable water zones or to the surface.

Similarly, in chemical waste disposal wells the injected fluids could enter fresh water strata unless they are effectively confined. The waste fluid, if not confined, could also corrode the exterior of the casing and create other difficult fluid control problems within the well in question or other wells problems within the well in question or other wells in the vicinity.

Many effective well designs are discussed in the literature. The integrity of many wells is quite satisfactory initially, since good zone isolation is provided. Unfortunately, in some cases the initial provided. Unfortunately, in some cases the initial competent state is very short-lived due to the presence of one powerful factor, corrosion. presence of one powerful factor, corrosion. Two targets of corrosion, assuming that a geological strata compatible with the effluent was selected, are the tubular hardware in the well and the cement used to secure the pipe in place and seal off extraneous and offensive zones.

Injection tubing in disposal wells receives the longest and most intimate contact with the corrosive effluent. It is therefore mandatory that it be completely inert to the injected fluid.