| Popis: |
Pitting corrosion on the tubing ID has caused failures of CT strings in operations across every operating region, with unconventional plays in North America being especially affected. A localized coating that can be applied to the bias weldment has been developed to protect the most susceptible portion of the coiled tubing string from corrosion. This paper will discuss the development process for the coating as well as initial case histories. Steel is plastically deformed in the manufacturing process to make coiled tubing, and the product is repeatedly plastically deformed in operations. As a result, coatings have historically not been successful with coiled tubing due to insufficient adherence to the tubing, which is the substrate. Once the decision was made to pursue a localized coating, a test plan was developed to test different iterations of the coating including coating materials and application processes. The initial testing plan included checking for adherence to the substrate as well as resistance to acid with the goal of highlighting a methodology for a working prototype. The results of the testing plan are provided and were used to determine the path forward to commission a working prototype. Physical Vapor Deposition (PVD) was selected as the best method for application of the local coating. PVD operates by exciting a target within a vacuum chamber, which coats the substrate. Coiled tubing is a continuous product, which prevents the use of a traditional vacuum chamber. This development led to the creation of the first-ever vacuum chamber of its kind—one that does not entirely enclose the product. The working PVD prototype has been successfully installed at the manufacturing facility in Houston, and test strings coated locally on the bias welds have been created. The paper will describe the first beta-test strings that have been released to the field and any reported observations from the CT service companies. This paper describes a new processing technique for the manufacturing of coiled tubing. Initial results show that the coating can dramatically improve operations, especially the prevention of unexpected failures with minimal cost impact to the coiled tubing operator. |
