Continuing Application of Torque-Position Assembly Technology for API Connections

Abstract

API threaded casing and tubing connections are expected to maintain structural integrity and sealability performance throughout the life of the well. Current industry standards specify thread dimensions and tolerances, but the critical makeup operation is specified with either torque-only or standoff (position) control. Variation among individual pin/coupling geometry combinations makes either of these makeup control processes inadequate to assure the expected structural and sealability performance of the connection. One operator developed and for the last 20 years has been using a quality control process for makeup that combines torque monitoring and a measurement of final assembly position. This assembly method, called Torque-Position, has provided gas-tight strings for critical well applications worldwide.Torque-Position assembly parameters were developed for tubing external upset (EUE), casing long thread (LTC), casing short thread (STC), and buttress (BTC) connections using advanced nonlinear finite element analysis and physical testing. Procedures were developed for easily implementing the assembly parameters for coupling buck-on in the mill and for final makeup at the rig floor. These procedures include painting a narrow circumferential band on the pin end behind the threads and watching for the face of the coupling to fall within the band at the end of the assembly operation to validate the position. Simultaneously, makeup torque is measured with an electronic load cell.The operator will continue to use Torque-Position assembly parameters and implementation procedures and hopes that publication will lead to wider application of the technology. This paper will describe lessons learned over the past 20 years to ensure successful application of Torque-Position makeup technology.