This paper reviews the mechanisms of initiation and the prevention of TLC. Practical multi-faceted techniques based on the most recent research and developments will be described and then illustrated using documented sources to arrive at best practices for control of this significant corrosion manifestation.
The application is in the complex corrosive environment in multi-phase and stratified flow pipelines (including gathering lines) that are frequently observed in new shale play production. The sizings of pipelines have become a critical factor to meet the current and future projected production rates. Especially where pipelines may be under-sized there is preferential attack in the top of the pipeline when water condenses and provides the electrolytes for acid gas and vapor attack on the steel surfaces.
Conventional corrosion inhibition methods (continuous or intermittent injection) are frequently not effective since physical contact of the inhibitors is difficult to achieve in multiphase flowing systems at the top of the line. In addition, the pipelines must be piggable to be properly cleaned and treated and traditional slug or continuous treatment methods have been found to not be adequate where conditions exist for TLC to occur.
Several innovative methods are being developed to provide effective and long lasting protection to the entire pipeline surface. Included are the use of pig trains with inhibitor slugs, inhibitor containing gels and foams and special pigs that provide a 360° spray of inhibitor chemicals. The newer methods will be compared with the other technologies.
The rapid expansion of the production of oil and gas from unconditional sources requires the annual construction of thousands of miles of new lines. These will experience a bewildering and changing range of conditions that will require the use of new and innovative internal corrosion protection methods described here that have been proven in field applications.