Premium threaded casing and tubing connections are expected to maintain structural integrity and sealability performance throughout the life of the well. Industry and various company standards for evaluating connection performance via physical testing on specific size/weight/grade combinations have been optimized. The industry now seeks methods to infer performance for combinations that have not been tested, based on completed tests. Time and cost savings are realized by extending test results within a family compared with multiple individual evaluation programs. One operator has implemented an approach to evaluating a family of premium connection designs across a range of size/weight/grade combinations. This approach includes a comprehensive review of the threading specifications within the family to provide a consistent design approach, finite element analysis of all of the family members within the range under extreme tolerance and load conditions to evaluate the consistency of performance, and rigorous physical testing of combinations representing the boundaries of the range or worst cases within the range. The operator has confidently assigned performance envelopes for several premium connection design families. Physical testing and finite element analysis evaluations assessed design and performance consistency, and established specific design-family-specific performance criteria. This paper will describe the process implemented to provide appropriate performance assessment of a connection product family for which all size/weight/grade combinations were not tested. Connection Performance Performance is just one of many factors that must be considered when selecting a specific connection thread design for a well casing or tubing application. Some well designers seek connections that are as strong as the pipe body; however, some connection designs remove enough material during threading that the assembled connection does not provide structural integrity equal to that of the pipe body on which it is threaded. Also, connections represent a potential leak path at the ends of each joint. ExxonMobil affiliates ("ExxonMobil") operating with many different well types and applications worldwide, have taken the approach of determining an envelope for each threaded connection based on structural integrity and sealability performance limits under combined load conditions, and ensuring that the anticipated loads from the well application are within the envelope. Fig. 1 is an example of a generic connection envelope that describes the structural and sealability performance of a specific connection. The sizes of the different sealability regions are determined by evaluating the connection's gas or liquid seal integrity for a load combination (i.e., axial and net pressure). The well designer determines design scenarios anticipated over the well's life and calculates the corresponding loads. These loads are plotted on the seal envelope corresponding to the fluid type for that design scenario. If all the loads fit within the appropriate envelopes, that connection design is suitable for the application. A challenge for the well designer and the industry is to determine accurate performance limits for a connection as economically as possible. A typical approach is to create geometries (specimen threads or an analysis model) representing extreme tolerance combinations within the connection design and then subjecting the geometries to combined load conditions in the test lab or in the analysis that exceed anticipated downhole conditions. The true seal integrity performance envelope of a connection may extend past the connection manufacturer's uniaxial ratings or even past the triaxial yield ellipse of the pipe body, although this latter performance may be difficult to validate during physical tests. The well designer wants to know the absolute limits for the connection even if other design constraints will keep the loads from approaching those limits.

American Petroleum Institute (API) threaded casing and tubing connections are expected to maintain structural integrity and sealability performance throughout the life of the well. Current industry standards specify thread dimensions and tolerances, but the critical makeup operation is specified with either torque-only or standoff (position) control. Variation among individual pin/ coupling geometry combinations makes either of these makeupcontrol processes inadequate to ensure the expected structural and sealability performance of the connection. One operator developed, and for the last 20 years has been using, a quality-control process for makeup that combines torque monitoring and a measurement of final assembly position. This assembly method, called TorquePosition, has provided gas-tight strings for critical well applications worldwide.Torque-Position assembly parameters were developed for tubing external upset (EUE), casing long thread (LTC), casing short thread (STC), and buttress (BTC) connections by use of advanced nonlinear finite-element analysis (FEA) and physical testing. Procedures were developed for easily implementing the assembly parameters for coupling buck on in the mill and for final makeup at the rig floor. These procedures include painting a narrow circumferential band on the pin end behind the threads and watching for the face of the coupling to fall within the band at the end of the assembly operation to validate the position. Simultaneously, makeup torque is measured with an electronic load cell.The operator will continue to use Torque-Position assembly parameters and implementation procedures and hopes that publication will lead to wider application of the technology. This paper will describe lessons learned over the past 20 years to ensure successful application of Torque-Position makeup technology. API Thread StandardsThreads intended for downhole application in well casing and tubing service are specified in API Specification 5B (API SPEC 5B 2008). Specification 5B includes dimensions and tolerances of the threads and thread forms, as well as gauging and inspection guidance. Several thread profiles are specified in the standard; however, the most common examples are BTC and 8 round. BTC features a more-rectangular thread form that is tapered, while the 8-round thread features a 60° flank angle with rounded roots and crests, and it is also tapered. The 8-round thread form is used in STC, LTC, and EUE connections. Millions of feet of all these connections have been run in all types of wells around the world since API first standardized them in 1939.The BTC and 8-round thread form specifications have not changed much over the decades, but machine-tool capability and computer-numeric-controlled (CNC) lathes have made these threads more precise. Gauging practice defined in API Specification 5B and Recommended Practice 5B1 (API RP 5B1 2004) requires various measurements such as pitch diameter, taper, and thread length. API thread forms rely on radial interference between the mating pin and c...

API threaded casing and tubing connections are expected to maintain structural integrity and sealability performance throughout the life of the well. Current industry standards specify thread dimensions and tolerances, but the critical makeup operation is specified with either torque-only or standoff (position) control. Variation among individual pin/coupling geometry combinations makes either of these makeup control processes inadequate to assure the expected structural and sealability performance of the connection. One operator developed and for the last 20 years has been using a quality control process for makeup that combines torque monitoring and a measurement of final assembly position. This assembly method, called Torque-Position, has provided gas-tight strings for critical well applications worldwide.Torque-Position assembly parameters were developed for tubing external upset (EUE), casing long thread (LTC), casing short thread (STC), and buttress (BTC) connections using advanced nonlinear finite element analysis and physical testing. Procedures were developed for easily implementing the assembly parameters for coupling buck-on in the mill and for final makeup at the rig floor. These procedures include painting a narrow circumferential band on the pin end behind the threads and watching for the face of the coupling to fall within the band at the end of the assembly operation to validate the position. Simultaneously, makeup torque is measured with an electronic load cell.The operator will continue to use Torque-Position assembly parameters and implementation procedures and hopes that publication will lead to wider application of the technology. This paper will describe lessons learned over the past 20 years to ensure successful application of Torque-Position makeup technology.