One of the most important functions of a tubular connection is sealability.
This is especially the case for premium connections that are commonly used in
the demanding conditions of high-pressure/high-temperature (HP/HT) and
thermal-well applications. Sealability, therefore, also is one of the most
important criteria used during connection qualification in which the capability
of the connection is verified for the characteristics of the application.
During qualification tests, it has been found that breakdown in connection
sealability can be traced to damage on the primary seal surface, which can
eventually develop into a leak path.
Ultrasonic-inspection technology can be used to provide a means to obtain
nonintrusive measurements of contact stress between two mating metal surfaces
separated by a thin lubricating film. While the technology has a wide scope of
potential applications in this respect, the technology has been specifically
developed to measure seal-surface-contact stresses inside oilfield tubular
This application of ultrasonic technology has been used numerous times
during connection-qualification programs to assess the quality of the
contact-stress band in premium connections. During these analyses, the
technology has been able to detect seal-surface damage in premium
This paper will cover the basic concepts of premium connection design, along
with some of the issues that can affect the sealability of premium connections.
As well, this paper will include an overview of the use of ultrasonic
technology as a technique to assess the contact stress along the metal-to-metal
seal band of a premium connection and methods used to monitor changes in the
contact-stress profile induced by many installation and service loads.
© 2009. Society of Petroleum Engineers
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- Original manuscript received:
8 August 2007
- Meeting paper published:
11 November 2007
- Revised manuscript received:
21 April 2008
- Manuscript approved:
30 April 2008
- Published online:
23 July 2009
- Version of record:
23 December 2009