No abstract

No abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractNondestructive Inspection of coiled tubing (CT) and coiled line pipe (CLP) is not only essential in assuring product quality, but also can be useful in determining physical attributes. In this paper are discussed some non-invasive methods that have been found to be useful in assessing these products.

The coiled tubing (CT) industry continues to operate in deeper and higher-pressure wells.1 Under these demanding service conditions, performance and reliability of the tubing are essential. This paper discusses field service and other events that led to an aggressive plan to introduce new inspection techniques that will help assure a higher level of performance of coiled tubing strings. The enhanced inspection techniques being instituted include inspection by the tubing manufacturer of the incoming strip and continuous phased-array ultrasonic inspection of the seam weld. In addition, the traditional through-hole calibration standards were upgraded with more realistic discontinuities to help ensure that the produced tubing is defect-free. The paper also discusses the important requirements of string management and maintenance procedures. A key to the success of this ongoing program has been the synergistic activity between the service company and the tubing manufacturer. Introduction Recently, the CT industry has begun to perform service work on deeper and higher-pressure wells. It is not uncommon to rate tubing for use at 10,000-psi. Previous experiences with high-pressure, high-temperature (HPHT) strings, however, have strongly indicated that additional testing of coiled tubing is required to ensure the integrity of the tube wall throughout its service life. Upon review of the issues, it was decided that both short-term and longer-term solutions and actions were required. Likewise, string management and tubing maintenance issues were recognized as essential components in completing the mission of providing reliable tubing to the CT operators. This paper outlines the steps taken by Quality Tubing, Inc. (QT) and Halliburton Energy Services, Inc. to assure tubing integrity from manufacture through the life of the tubing. Experiences Highlight Need for Enhanced Inspection Involvement with several string problems over the last year highlighted the need for increased assurance of seam weld quality as well as a need for higher assurance of tube body integrity. This assurance is vitally needed, of course, for HPHT strings but the case can also be made that all work strings deserve total integrity assurance. The primary incident that suggested that enhanced inspection of milled strings was needed occurred in August 2000 in Aberdeen. A leak was detected during pressure testing of a 1.750-in. OD QT-1000 string (12392) in preparation for an HPHT job. The string was relatively new (roughly 8% fatigue life utilization at the leak point, Fig. 1). It should be noted that leakage was not apparent after pressure testing at 5,000 psi but was only identified after testing at pressures in excess of 10,000 psi. The original mill hydrotest pressure was 11,800 psi, at which time there was no leak. A formal investigation concluded that the leak was the result of small weld-line imperfections in the longitudinal seam weld. Evidence collected during the failure analysis suggested that the string contained lack-of-fusion defects after milling,2as opposed to initiation-of-weld cracking during service work.

A new non-contact CT assessment system was placed in service in 2010, measuring wall thickness, diameter, ovality, and detecting imperfections in the wall of ferromagnetic steel tubing. The unit is capable of assessing both new tubing for compliance with API 5ST (Specification for Coiled Tubing)1supplementary requirement SR37, and also in-service tubing for erosion, corrosion and other imperfection conditions. The unit has the advantage of being able to assess the effect of flaws on tubing life via the Flexor programme. A review of results obtained with the new tool when used to assess both new and used CT will be presented. Knowledge of the condition of the tubing at all stages of its life should be of great importance to owners of tubing when deciding upon future tubing use.