Fight Corrosion by Educating Oilfield Operators

Corrosion in the oilfield can be caused by many sources: H₂S, HCl, CO₂, SO₂, brinish disposal water, highly acidic soil conditions and many others. Corrosion reduces productivity, and causes downtime for maintenance, or worse, replacement. Each year, corrosion costs oil and gas operating companies billions of dollars in lost revenue and reduced operating profit.

Operating companies involved in oil and gas production have to abide by safe and timely production schedules. In many instances, fluids are so highly corrosive that most tubulars will experience greatly diminished life cycle without some sort of protection.

There are ways to minimize the effects of corrosion on the internal surface of oilfield tubulars. But before making any specification for your application, you should have some basic knowledge of the two most commonly used forms of protection: coatings and liners.

Internal plastic coatings (IPC)

Originally, most internal coatings were organic solvent based, however, pressured by the Clean Air Act in the 1970s, the industry implemented powder coatings to cut use of solvents, hence reducing emissions. Efforts to coat with powder are often unsuccessful because the adhesion of coating to the pipe is often ineffective.

These coatings are thin and unable to resist impact, thus culminating in aggressive localized corrosion. In addition, the coatings are not of universal thickness or found throughout the entire product. Over time, these imperfections grow, until there is a complete failure of the piping that would shut down the system.

While many of the powder coatings have improved, it is essential to understand what kind of parameters must exist to ensure success. This chart compares IPC and glass reinforced epoxy (GRE) liners:

GRE systems are adaptable to a large range of environment and able to accommodate a changing injection profile.

Before choosing powder coating options, it is recommended qualification tests be conducted. Keep in mind many coating standards originated from the external coating business. Plus, there tends to be confusion over proper procedures by the extensive number of ANSI, AWWA, API, NACE, DIN and ASTM standards that are associated with coatings and paint. These may not be suitable for internal coatings. Take care that these standards are not confused with one another and the testing during fit for purpose trials is relevant to the system in question.²

Internal tubular polymer liners

In order to properly select a liner, you must accurately assess the entire environment that the liner will be exposed to during well servicing and treating operations before making a decision. Without a complete evaluation of the well, environment specifiers could actually reduce the allowable operating temperature and pressure for a liner.

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Thermoset GRE liners and polyvinyl chloride (PVC) liners for lower temperature applications are the most common options. Recent developments include a family of liners that vary in chemical resistance but share a primary distinguishing feature — the allowable service temperature of each liner material.

Below is a graph of a comparison between GRE and other liners:

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Overall, GRE liners have solved the problem faced by other tubular corrosion control options. GRE lining systems have a proven track record in a great number of demanding environments including water injection, CO₂ injection, gas production, gas-lifted oil production and chemical disposal wells, onshore and offshore. They have outstanding performance history in harsh environments containing CO₂ and H₂S. GRE liners have successfully prevented corrosion in gas production wells with high temperatures.

One GRE liner that has proven to be successful in the field is fabricated exclusively by Duoline Technologies. The Duoline liner is manufactured with a filament winding and high temperature cure process. The fiberglass-epoxy lining system has over 33 years of accumulated field history.

Featured benefits of Duoline Technologies GRE liners:

Duoline is manufactured in an ISO facility; full traceability
Duoline is cured from the inside out thus reducing air pockets and permeability to the greatest degree
Duoline is manufactured by Duoline from raw materials, thus Duoline has full quality control over raw materials
Duoline is 100 percent holiday tested and 100 percent drifted
Duoline has over 30 years experience with the GRE system

Duoline is manufactured at a state-of-the-art facility, using proven technologies and made in the USA.

The liner has proven to be the most abrasion-resistant coating or lining product in downhole wireline trials in deviated wells. It is acid compatible, resistant to impact, resistant to gas service failures common to other coatings or linings, premium connection compatible, chemically resistant and tolerant to common tension and bending loads.

Duoline Technologies GRE liners were installed in an Offshore Gas Injector well in the Liverpool Bay in 1998 with a well depth of 5,700 feet with an injection rate with H₂S and CO₂ present at 53 degrees C.

In order for oil and gas companies to lower overall tubular capital expenditure costs, reduce tubular maintenance and corrosion prevention, they must begin with a solid knowledge of the best options available to them. The most effective way to minimize the cost of corrosion on the internal surface of oilfield tubulars starts with a solid knowledge of coatings and liners.

One of the key elements in the decision-making process will be the environment the tubulars will be operating in. There will be environments where coatings could be the choice for protection, and for others liners are the better choice. However, even among liners there are key differences. Keep in mind that for over 30 years GREs have proven to outperform other polymers in protecting tubulars from corrosion and abrasion.

References:

1-http://books.google.com/books?id=XD8ynYRTQ8oC&pg=PA227&lpg=PA227&dq=coatings+for+internal+surfaces+oilfield+tubulars&source=bl&ots=m2sXAm0jhz&sig=tCYBOhtTrZ7gHdRWahWV61AbOUg&hl=en&sa=X&ei=s5uCUYD6EYSC8ATM2YCwCg&ved=0CI8BEOgBMAk4Cg#v=onepage&q=coatings%20for%20internal%20surfaces%20oilfield%20tubulars&f=false

2-http://wiki.iploca.com/display/rtswiki/11.5+Internal+Coating

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