Producing hot, high rate, high pressure wells can subject tubing threads to compression and tensile forces that exceed the scope of current published data and specifications.
Mobil Oil Indonesia, contractor to Pertamina, Indonesia's National Oil Company initiated the development of test apparatus and test procedures to simulate actual downhole stresses on tubulars. Mobil's intention was to fill the gap in the published data and to determine the cause of thread leaks in Aran wells. It was postulated that the leaks were the result of extreme compression and tensile forces acting on the tubing threads. Weils completed in the Arun Limestone are capable of producing 250 MMSCFD at well-head pressures and temperatures of 4000 psi and 347° F. Forces on the tubing string varying from 350,000 lbs compression to nearly 500.000 lbs tension during pressure and temperature reversals between conditions of shut-in, producing and stimulating.
The test apparatus and procedure can detect thread leaks while subjecting test specimens to:
7500 psi internal pressure
Compression and tensile loads up to 500,000 lbs.
Temperatures up to 350° F.
Quenching of internal pin surface such that the temperature is reduced from 350° F to 150° in
Application of the equipment and test procedures confirmed the failure mechanism and helped evaluate other thread designs for use in the harsh Aran wellhore environment.