Qualification Methodology for Advanced Rotary Shouldered Threaded Connections

A qualification methodology for advanced rotary shouldered threaded connections is presented. It covers physical tests of connection prototypes and virtual tests with modeling and simulation techniques. The methodology had been applied to qualify a fatigue-resistant threaded connection design that has recently been released for field testing. The qualification process consists of in-lab makeup and breakout tests, on-rig makeup and breakout tests, sealability tests, fatigue tests, torsional yield limit tests, and tensile capacity tests. During the development of the design, modeling and simulation techniques were extensively used to optimize the design prior to physical prototyping and testing. Some of the qualification tests, such as torsional yield limit tests and tensile capacity tests, were carried out by using advanced modeling and simulation techniques. Because fatigue tests under nominal loads take a long time to complete, accelerated fatigue tests under calculated overloads were conducted to assess whether the design would meet the fatigue life requirements with low risk. After positive results were obtained from the accelerated fatigue tests, nominal loads required by the product specifications were then applied to complete the qualification fatigue tests. It was found from the experimental results that the predicted performance of the connections, such as fatigue life, critical sealing pressure, and breakout torque, matched with the physical test results well. Despite the fact that numerous rotary shouldered threaded connection designs have been developed in the oil and gas industry, there has been no formally defined qualification procedure for such designs. The objective of this paper is to introduce, for the first time, a systematic and complete qualification procedure for rotary shouldered threaded connections.