LEAKAGE RESISTANCE ENVELOPES OF API 8 ROUND CASING CONNECTIONS USING FE ANALYSIS

Abstract

LEAKAGE RESISTANCE OF CASING CONNECTIONS CAN BE EVALUATED BY EXTREMELY EXPENSIVE TESTING PROCEDURES. ALTHOUGH TESTING IS REQUIRED FOR CONNECTION VALIDATION, SIGNIFICANT AMOUNT OF RESOURCES CAN BE SAVED BY COMPLEMENTING TESTING WITH FINITE ELEMENT (FE) ANALYSIS. IN THIS REGARD, A BROADLY ACCEPTED CRITERION TO CHARACTERIZE LEAKS IN FE SIMULATION IS STILL REQUIRED. THIS PAPER PROPOSES AN OBJECTIVE AND ACCURATE CRITERION TO CHARACTERIZE LEAKAGE RESISTANCE OF CASING CONNECTIONS IN AXISYMMETRIC FE SIMULATION. THE CRITERION IS BASED ON STAB FLANK CONTACT PRESSURES AND STAB FLANK ENGAGED LENGTH PARAMETERS. THE CRITERION IS TESTED IN APPLICATION TO API 8 ROUND LTC CONNECTIONS (5 ½ J55 14LB/FT), AND CONFRONTED WITH TEST RESULTS. LEAKAGE ENVELOPES ARE OBTAINED CONSIDERING MAKE-UP TORQUE AND TENSILE AXIAL LOADS. THE INFLUENCE OF TAPER ON CONNECTION SEALABILITY IS ALSO INVESTIGATED. THE LONG TERM GOAL OF THE INVESTIGATION IS TO DERIVE PROBABILISTIC LEAKAGE ENVELOPES OF CASING CONNECTIONS CONSIDERING MANUFACTURING TOLERANCES, EFFECT OF THERMAL CYCLES, AND SEAL OVALIZATION DUE TO BENDING DURING ASSEMBLY.