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The heavy weight drill pipe, one of the most expensive components of the drill string, is exposed, beside fatigue and corrosion, to an intensive wear process as a result of the friction with the inner wall of the casing or the borehole wall, that lead to a drastically decrease of it durability. In order to improve the durability, the worldwide specialists apply the hardbanding technology to increase the heavy weight drill pipe wear resistance. The major problem raised by the hardbanding process is the selection of the most suitable wear resistant alloy and the optimum hardbanding technology. The present research work investigate the possibility of hardbanding the heavy weight drill pipes by using the gas metal arc welding process, taking into considerations three different wear resistant materials with the trade name ARNCO 100XT, ARNCO 300XT and FLUXOFIL M58.

This paper brings forward the results of theoretical and experimental investigations performed to determine the causes that led to the failure of 20 inches threaded casing connections during the tubing of the Lupşa Sat No. 1 oil well, Romania. The failure occurred due to the breakout of the threaded casing connections assembled in the factory. In order to establish the main causes of failure, theoretical investigations were taken into consideration to highlight the influence of the thread element errors on the correct make-up casing pin–coupling (box) conditions and to the axial tensile strength of the threaded casing connection. In addition, experimental investigations were performed on the failure casing connections, consisted of measuring the dimensional characteristics of the thread elements to determine the performance and monitor the technical condition of the tubular material used in the petroleum industry.

The present researches established the failure causes of the drill string, used in corrosive environments with H2S, in an oil field, by initiating fatigue cracks from the corrosion points on the inner surface of the drill pipes, which favoured the diffusion of hydrogen, the brittleness of the material and the brittle fracture.