Shipment
Tubing can be damaged during shipment, at the wellsite, and during running and pulling. API RP 5C1[1] Secs. 2 and 3 should be followed closely. For transportation, slightly different procedures are needed to prevent damage depending on whether shipped by water, rail, or truck. Care must be taken in unloading and storage. Thread protectors must be installed properly and rough handling avoided. Tubing should be stacked on racks following proper procedures, and tubing in storage should be inspected periodically and protected from corrosion. In general, the high-strength materials are more susceptible to handling damage.
Running and pulling tubing
Numerous factors must be considered when running and pulling tubing. The operating personnel should ensure that good practices are followed. Each length of tubing should be measured and drifted in compliance with American Petroleum Institute (API)/International Standards Organization (ISO) specifications. The tubing should be handled with thread protectors, which are not removed, until the tubing is ready to stab. Adequate thread cleaning is essential for proper connection makeup and pressure-tight strings. Apply a good thread compound but avoid excessive amounts. Collar-type tubing elevators are adequate for API non-beveled couplings; however, slip-type elevators are recommended when running tubing with beveled couplings, special clearance couplings, and integral joint tubing. Check spider slips to ensure they will not damage the tubing body.
Use of power tongs is necessary to obtain consistent makeup torque. Properly maintained, installed, and calibrated tongs are essential. Follow the API recommended tubing makeup torque for non-upset, external-upset, and integral-joint tubing. Follow the manufacturer ’ s recommendations for specialty joints. However, the makeup torque may vary depending on the thread coatings and lubricant type; thus, adjustments in makeup torque values are sometimes required. Torque values listed in API RP 5C1 apply to tubing with zinc-plated or phosphate-coated couplings. For tin-plated couplings, use 80% of the listed values as a guide for proper makeup. To establish the correct torque for API tubing threads, make up the first few joints to the recommended values and examine the connection. There should be no excessive heat, approximately two turns beyond the hand-tight position with all threads buried. Back out the connection (noting torque) and check threads for galling. If needed, adjust torque and repeat. Use the established makeup torque for the remainder of the string.
To obtain maximum leak resistance with the API-tapered thread, the pin end of the connection is made up to slightly beyond the point of yielding. Consequently, API EUE connections may make up slightly more on repeated operations. The problem of makeup is to use torque that is sufficient to provide the needed seal without permanently damaging the connection. Good experience has been reported with the torque-turn method with API EUE tubing. In the torque-turn method, the power tongs are calibrated to record both the number of turns and the torque to make up the API tubing coupling to the point of yielding. In many of the proprietary connections, there must be ample makeup torque so that the metal-to-metal seals are energized. Check with the manufacturer for makeup guidelines.
Thread compound
API-modified thread compound generally has been accepted for a wide range of service conditions over many years. The placement of thread compound at the root of the rounded API threads with the bearing pressure on the thread flanks (the interference fit, power tight makeup) produces the sealing mechanism. The thread compound also provides the lubrication to deter galling. The compound is a mixture of metallic and graphite powders uniformly dispersed in a grease base. API RP 5A3[3] and ISO 13678[4] provide the means for evaluating the suitability of thread compounds for use on API round threads in high-pressure service. For specialty connections, consult with the manufacturer on the proper thread compound. Environmentally non-damaging thread compounds meeting API thread-compound performance requirements are available.
Evaluation procedures for connections
Evaluation procedures for casing and tubing connections tests to be performed to determine the galling tendency, sealing performance, and structural integrity of tubular connections, especially for high-pressure application are under study. See ISO/DIS 13679.[5] Table 1 shows example relationships between test classes and service applications. Other relationships may be more appropriate for individual users. Class IV connections are intended for the most severe application, and Class I connections are intended for the least severe application.