Numerical Modeling and Experimental Validation of Advanced Rotary Shouldered Threaded Connections

Song, Fei (Schlumberger) | Du, Michael H. (Schlumberger) | Li, Ke (Schlumberger)



To mitigate the risk of twistoff during high dogleg-severity (DLS) drilling and to reduce cost of service delivery induced by frequent recuts, an advanced rotary shouldered threaded connection design with significantly enhanced fatigue life over existing API connections has recently been developed and released for field operation. Modeling and simulation techniques had been extensively used to drive the design and qualification processes. In this paper, an overview of the numerical modeling methodology and its experimental validation is presented with an emphasis on the key functional requirements of the design.

The newly developed connection design involves an optimized thread form and an advanced manufacturing process. Finite element analysis (FEA) was heavily used to optimize the design prior to physical prototyping and testing. High-fidelity modeling methods were developed, and comprehensive numerical analyses were performed to digitally evaluate the performance of the new design, including fatigue resistance, galling resistance, combined load capacity, sealability, and so on. The FEA models had very well predicted the performance of the new design, which was later validated through full-scale experimental tests. Several qualification tests, such as torsional yield limit test and tensile capacity test, were carried out completely digitally. As a result of the extensive modeling and simulation work conducted, the connection design met all requirements in one iteration.

The work presented in this paper represents a successful example of model-driven product development, which significantly reduces development time and cost. It is the first time that a high-fidelity modeling methodology, in conjunction with full-scale experimental validation, is introduced for advanced rotary shouldered threaded connections in the oil and gas industry.