Performance of tubular connections under the loading conditions of horizontal wells

This study deals with the negative effects of bending stress and casing wear on tubular connections. The joint strength of three connection types, API long round thread (LTC), API buttress thread (BTC), and typical premium joint (PJ), was measured with a full-size combined loading tester. Measurements were also made for the connections simulating wear induced by drilling operations. The sealing ability of the connections were evaluated under bending and wearing conditions. Numerical simulations were undertaken to investigate the failure mechanism of the connections. The results indicate that LTC joint strength is lowered by bending, though that of BTC and PJ is not degraded. Joint strength is reduced in direct proportion to the wear area ratio of the pipe body. In sealing ability, only the premium connection maintained leak resistance under combined loading with bending. Axial loading is more detrimental to sealing integrity than the bending moment. In conclusion, the connection performance data can be useful in designing safer horizontal well casings.