An Apparatus and Test Procedure for Qualifying Expandable Connections for Challenging Applications
Authors: DeLange Richard , Zhou Shaohua , Choi Ho Jin , Evans Ed , Osburn Scott 
Published: October 2009

To add more application value to operators, expandable liners have been installed recently in more and more challenging environments, particularly from vertical to horizontal through a build-section. To date, there is neither adequate test data nor industry standards corresponding to such applications, especially when the bent liner is fully supported and is constrained at both ends (a fixed-fixed bent expansion). Because of the lack of accurate test lab simulations of the expansions followed by connection qualification testing, application parameters for horizontal expandable liners with deviated sections are not well defined.

This project was established to develop an apparatus that would allow generating and maintaining a constant curvature during and after expansion so that meaningful test data can be generated on 5.5 in. threaded connections and pipe in various states of downhole condition. The connections would be performance tested after expansion using test formats similar to the industry standards used to qualify unexpanded threaded connections.

Expansion of 5.5 in. expandable pipe and connections were conducted to accurately simulate downhole conditions for horizontal applications (unbent) and deviated wellbore applications (bent to a 12°/100 ft constant radius). These two conditions were each expanded with and without axial constraint (fixed-free versus fixed-fixed). Pipe samples without connections were also expanded under these same conditions for metallurgical laboratory testing. The curved laboratory samples with connections were bent along a new bending beam's curved surface, cone expanded and then tested based on requirements outlined in ISO 13679. The bending beam apparatus allows performance testing of expanded and bent samples without changing the curve shape, an accurate laboratory simulation of downhole conditions in a deviated wellbore.

Because the testing requirements outlined in ISO 13679 require combinations of loading and internal pressure, keeping the test sample fastened to the beam to maintain curvature was an important step for accurately evaluating the connection's performance. The ISO 13679 format requires applying large tension loads which would tend to straighten out the test sample if it was removed from the apparatus before testing. Unsupported, these tension loads would generate unnatural bending loads on the connections during the tests, a condition not expected downhole.

This paper presents the results of a new bending beam apparatus and test procedure for qualifying threaded connections that were expanded and tested under conditions that are accurate simulations of the downhole environment. Additionally, the paper presents the results of the tested connections and material testing accomplished with the new test system.

To increase the reliability of expandable tubular technology and address the previous challenges of connection failures with expandable liners in deviated wellbore sections, this type of work is important to the operators and manufacturers for determining the appropriate parameters or operating envelopes for successful expandable liner installations. The work will provide further significance related to testing requirements for these challenging and critical applications.