This paper presents a comprehensive summary of the different techniques for increasing the available torque of existing drilling products, the limitations of these techniques and the best practices that can be implemented to reduce risks when using drilling tubulars beyond the API recommended make-up torques.
The torsional strength and make-up torque of a threaded connection are traditionally calculated by only using inherent attributes of the connection, such as the thread design, the yield strength of the connector's material, and the cross critical section of the connector. However, the design of a connector is not the only option to increase its operational torque. Stress balancing considerations and the thread compound friction factor can also help increase operational torque. The recommended make-up torque for rotary shouldered connections is typically defined by stressing those connections to 60% of their torsional strength, thus leaving a margin for using a higher make-up torque‒and hence reaching a higher operational torque. Another option to increase the available operational torque is to use a thread compound with an increased friction factor. API thread compounds are designed with a friction factor of 1. Because of this, when using a thread compound with a higher friction factor, the applicable make-up torque has to be corrected.
Although stress balancing and the thread compound friction factor considerations can easily and economically increase the available torque of a connector during drilling and allow having more versatile products on the rig, these practices can also carry some risks.
Compilation of lessons learned from torque-increasing techniques for rotary shouldered connections and compatibility considerations with rig equipment when using them.