A Proven Technique for Economic, In-Place Casing Lining and Repair
Authors: King George E. , Vloedman Jack , Ford Gary , Westermark Robert 
Published: December 2007

Abstract
This paper deals with a new technique for economic in-place lining of casing to prevent some forms of corrosion and to seal leaks. Casing leak repair has become a very important, but often exasperating problem. Conventional repair methods are plagued with only sporadic success and relatively high average costs. Repeat leaks are common, some within only a few months of a successful treatment. A new technique, however, proven now in over 80 wells, involves economical, very rapid, in-place lining of the well, often from top to bottom, with a continuous tube of abrasion and corrosion resistant, high density polyethylene or other material. The tube (seamless, with single tube lengths to over 4,000 ft) is diameter reduced at the surface by running through a multilevel set of rollers and kept reduced by application of weight-induced tension until it is run to the desired depth. Once the tension is released by setting the weights off on a packer or the bottom of the well, the polyethylene liner expands against the pipe, creating an internal, pressure tight seal. Successful use of the concept has been as both a repair technique and as a corrosion protective barrier that allows tubingless completions in wells that were tubing flow limited. It can be perforated, explosively severed, milled and even pulled if needed. Its use as a liner has been well documented in both injection well repair and in new completions on producing wells.
The paper covers candidate selection, design and application data from a data base that now covers over 80 wells with application depth from 1,000 to over 4,600 ft.

Introduction
Prevention of corrosion in tubingless completions or annular flow would increase flow potential and lower maintenance costs on many wells. Also, any process that offers near 100% success on top-to-bottom sealing of leaks in injection wells or high pressure producers would also be welcome. Beginning about three years ago, we began to experiment with an in-place casing lining system that has since proven to be fast, economical and very reliable for many wells.

HDPE
The bright spot is a new application of an old pipeline repair technology that has been tested and proven to be spectacularly successful as a single, in-place treatment with high density polyethylene, HDPE, to seal all the shallow casing leaks from the smallest coupling leaks to large holes (2 in. diameter). This new system incorporates a viscoelastic casing lining that is reduced in diameter at the surface, and then pulled into the well by weight to a depth of up to several thousand feet. When the weight (tension force that keeps the liner in a reduced state) is released, the liner expands against the steel casing reducing the chance of leak paths and generally offering a seamless "second skin" from the top to the bottom of the liner. The number of possible leak points is reduced from the endless possibilities in the hundreds or thousands of feet of pipe to just two points; top and bottom. The top of the liner can be fused to a special HDPE flange connection and sealed in the wellhead below the master valve or left as a "lap" joint. The liner bottom establishes a tight, low leakage bond to the pipe in the pressure tests conducted thus far. The type of damage that the liner can seal includes corrosion pits, leaking collars, small holes and even splits (although the outside pipe must be structurally sound to withstand pressure in the liner).
The polyethylene lining system and most other repair options are better at holding pressure in than keeping fluids out The pressure differential from inside to out (burst force) may be on the order of several thousand psi, dependent mostly on physical integrity and mechanical strength of the casing or the open hole that backs up the pressure sealing capacity of the polyethylene. P. 105^