Improving casing integrity with induction brazing of casing connections

Brazing technology allows metallurgical joining of dissimilar materials using a filler material. In this paper, brazing technology applied to casing connections is presented as an enhancement of existing (premium) connections and/or a replacement of metal/metal seals. The initial application was triggered by challenges with mechanical and pressure integrity after the expansion of casing connections. Creating a strong bond between the pin and the box could resolve this and remove the need for a metal/metal seal. Brazing was selected because of the combination of ductility and high bond strength and the relatively fast process to create the bond. The brazing process or the temperature/torque/time (TTT) process is performed using regular casing connections, a filler material deposited by flame spray and a flux. Two processes were developed, one for expandable (VM 50) grade material and one for quenched and tempered grade material. A rig-ready (Class 1, Division 1) prototype brazing system was developed consisting of an induction coil as the heat source, an environmental chamber to shield the hot work, and a modified power tong to provide torque. The results of a series of brazing trials on 8⁵=8- and 9⁵=8-in.-casing connections are presented. The brazed connections were subsequently capped, end-pressure tested, expanded (when applicable), and load cycled. It is concluded that both processes produced leak-tight casing connectors before and after expansion (when applicable), as shown by full-scale tests.