Summary
American Petroleum Institute (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 ensure 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 by use of advanced nonlinear finite-element analysis (FEA) 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.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
26 June 2010
- Meeting paper published:
21 September 2010
- Revised manuscript received:
13 November 2010
- Manuscript approved:
28 November 2010
- Published online:
26 May 2011
- Version of record:
15 September 2011