API RP 5C7
Recommended Practice for Coiled Tubing Operations in Oil and Gas Well Services
|Publication Date:||1 December 1996|
This recommended practice covers coiled tubing and associated equipment (see Figure 1) as well as applications (see 1.3). Coiled tubing sizes are specified by outside diameter (OD) and are currently available in ¾-inch OD through 3½-inch OD. Materials covered in this recommended practice are high-strength, low-alloy steels with specified yield strengths from 55 thousand pounds per square inch to 90 thousand pounds per square inch. Use of coiled tubing in onshore and offshore operations as well as critical and routine operations are discussed.
MATERIAL NOT COVERED
Due to the limited scope of this document, not all coiled tubing materials and applications are addressed here. Although some of the information presented could be relevant, alternate materials under development (such as titanium, corrosion resistant alloys and composite materials) are not covered. In addition, the applications listed in 1.4 are outside the scope of this recommended practice.
Coiled tubing applications covered in this document are as follows:
a. Cased hole workovers.
b. Cased hole drilling.
APPLICATIONS NOT COVERED
Coiled tubing applications not covered in this document are as follows:
a. Open hole drillings (balanced or unbalanced).
b. Open hole workover operations.
c. Pipelines and flowlines.
d. Control line.
e. Capillary tubing.
Material presented in this recommended practice is organized into five sections, including these general sections (1 through 4).
Section 5 covers design, care, and handling of coiled tubing as manufactured and prepared for delivery to the purchaser. The current processes of coiled tubing manufacture and high-strength, low-alloy steel materials used are reviewed. Mechanical and performance properties for new coiled tubing are also covered, along with a review of tapered string design and construction. Section 5 concludes with a review of the nondestructive inspection practices and tests commonly employed by coiled tubing manufacturers.
Section 6 addresses the serviceability issues related to performing coiled tubing operations, and offers recommended guidelines for coiled tube maintenance, record keeping, and derating. This includes a discussion of the unique characteristics of coiled tubing, such as fatigue, fatigue derating methods, changes in tube diameter resulting from bending while in service, derated collapse pressures due to ovality, and effects of corrosion and cracking of coiled tubing. This section concludes with a general discussion of the performance of welds in the coiled tubing string.
Section 7 addresses surface and downhole equipment used during coiled tubing operations. Equipment addressed includes coiled tubing injectors, tubing reels, hydraulic power supply (prime mover), tubing guide arches, well control components, riser stacks, high-pressure surface piping, and a review of tubing connectors for attaching tools to the coiled tubing.
Section 8 is a discussion of operational contingencies and suggested guidelines for performing coiled tubing services. Topics covered include pre-job preparation, rig up, entering the well, and potential operating concerns which may be experienced when performing various downhole services.