Accurate makeup of Rotary Shouldered Connections (RSC) isof most importance in achieving the best torque and axialforce transmission through the connection which optimizes itslifetime under downhole conditions. The makeup torque valueof RSC depends on the friction coefficient between the threadsand the parts of the shoulder that are connected during themakeup procedure. This friction coefficient cannot normallybe individually measured or determined, so that the APIRecommended Practice 7G gives an average recommendedmakeup torque based upon an assumed friction coefficient,adding a certain safety margin. Therefore, the majority of theRSC are being made-up with a torque value that differs fromthe connection optimum torque. This has two consequences:the lifetime of each connection is not maximized and thetorque and axial force values that can be transferred throughthe connection is different from the technical maximum thatthe connection is able to transfer if it was made-up with theoptimum makeup torqueThis paper describes a computer model that can be used todetermine the optimum torque at rig site. The model wasdeveloped at the Institute of Petroleum Engineering of theUniversity of Technology Clausthal and is based on more than300 tests on full scale specimens. Throughout the researchproject the authors found a new method of determining theoverall coefficient. A dynamic friction coefficient to achieve amuch better applicability of this method was introduced andthe way to determine is presented. This dynamic coefficient isthe key to compute the optimum makeup torque.Systems to makeup rotary shouldered connections are muchmore accurate than the traditional makeup with chains and rigtongs, thus reducing the damage of connections. State-of-theartdevices do not only allow the precise mechanized makeupof connections, but they also provide sufficient data to analyzethe quality of the connection make-up. The motivation behindthe research performed is the desire to make use of the datathat are already provided for the benefit of increased lifetimeof the connections and the reduction of drill string failures.A comparative evaluation of the proposed and the existing(API and Baryshnikov) methods was studied. The new methodout performed the existing ones. The new method can beimplemented in the new generation of computer controlledpower tongs to improve the makeup quality at rig site.
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