Shale plays continue to push the demand for OCTG connections that can achieve higher torque, tension, compression, and pressure ratings while remaining economical as the drive for lower well costs intensifies. These unconventional wells require new connection technologies and adapted testing protocols to ensure no downhole issues occur. The work presented in this paper focuses on a new locking-thread connection developed specifically to address the shale performance need.
The connection testing program has been based on the API TR 5SF June 2019 ballot draft. This new standard is being drafted by API Working Group 3081 specifically for shale applications and divides the testing into a sequence typical of operation including connection make-up, installation and running, stimulation, and production.
In addition, the connection needed to address an issue that Shale operations are commonly facing, i.e. inner diameter (ID) restriction. This phenomenon was investigated with torque and drag simulations and utilizing finite element analysis (FEA). Various conditions and locations in a typical well were analyzed.
By utilizing locking-thread connections, the new connection resulted in a significant increase in operational torque. The use of a thread seal allowed for a more economical design better suited for the application. This paper explains in detail which test conditions have been defined and successfully performed on the connection, aimed at being representative of all Shale play load sequences and usage.
ID restrictions are a result of unique combined loading in shale developments – high torque being applied in combination with tension and compression. This connection exhibits low risk of ID restrictions thanks to its high torque capacity and design features. The high torque capacity in turn, allows operators to push their laterals further as they move to torque to mitigate friction factors.
Additionally, a torque-tension relationship was investigated which is currently sparsely reported in any OCTG literature. This relationship suggests that the new connection could obtain higher torques under most conditions but would experience a reduction of torque capacity if high torque and tension loads were applied. This will help the operator to mitigate the ID restriction risk.
The testing protocol presented in this work sets an interesting reference for Shale connection testing as it is the most advanced testing seen in the industry for shale products, combining API 5SF guidelines with the API RP 5C5 2017 standard. This paper also provides the details of torque capacity evolution vs. tension and compression, allowing the user to have a more accurate model for connection suitability when combining with torque and drag simulations.