Defining coiled tubing limits -- A new approach

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:434036

Newman, K R; Sathuvalli, U B; Stone, L R; Wolhart, S

The burst, collapse and axial load operating limits for Coiled Tubing (CT) are currently established using the Von Mises incipient yield criterion. This criterion has historically been used to calculate the limits for oil country tubular goods (OCTG). The limits according to this criterion are based on the point at which the pipe material reaches a load state in which it begins to yield. Because of the bending that occurs when the CT is spooled on and off the reel, and when it is bent over the guide arch, the CT is already far beyond the yield point before it enters a well. Thus, this criterion does not really apply to CT. This paper describes a research project currently in progress. The purpose of this project is to define a new set of CT limits based on criteria other than incipient yield. This new approach to setting CT operating limits takes into account the internal residual stresses in the CT which are a consequence of repeated bending cycles and the accompanying change in material properties.

• Sponsoring Organization: Gas Research Inst., Chicago, IL (United States)
• OSTI ID: 434036
• Report Number(s): CONF-960525--
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
FIELD PRODUCTION EQUIPMENT
LIMITING VALUES
MECHANICAL PROPERTIES
OIL WELLS
PIPES
RESIDUAL STRESSES
STANDARDS
YIELD STRENGTH