Improving Casing Integrity by Induction Brazing of Casing Connections
Authors: Carpenter Chris 
Published: July 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 184703, “Improving Casing Integrity by Induction Brazing of Casing Connections,” by D. Ernens, H. Hariharan, W. van Haaften, H.R. Pasaribu, M. Jabs, and R. McKim, Shell, prepared for the 2017 SPE/IADC Drilling Conference and Exhibition, The Hague, The Netherlands, 14–16 March. The paper has not been peer reviewed.

Brazing technology allows metallurgical joining of dissimilar materials by use of a filler material. In this paper, brazing technology applied to casing connections is presented. The brazing process, or temperature/torque/time (TTT) process, is performed with regular casing connections, a filler material deposited by flame spray, and a flux. Two processes were developed, one for expandable-grade material (VM50) and one for quenched-and-tempered-grade material.

Introduction

Casing connectors continue to be a potential liability in complex wells that use premium connections or expandable liners. The technology presented in this paper applies brazing to casing connectors to improve leak tightness of American Petroleum Institute or premium connectors, ensure leak tightness after severe plastic deformation, and increase torque capacity.

The casing connector needed to have mechanical and pressure integrity before and particularly after expansion. However, the extreme plastic deformation reduced the critical cross section and the effectiveness of the metal-to-metal sealing mechanisms. This proved to be difficult to solve with only mechanical design considerations.

The bond needed relatively high shear strength and enough ductility to cope with the plastic deformation. Furthermore, the bond needed to be made quickly, should not alter the material properties of the expandable material, and should be compatible with standard rig operations. Multiple technologies were investigated to overcome these difficulties, including welding and gluing. However, among the technologies evaluated, only brazing provided the strength and ductility with the relatively high speed for making the joints approaching that of the standard casing running process.

Methods

Brazing Process. The brazing process is shown schematically in Fig. 1. The first step involves deposition of the filler material on the threads. This operation is carried out off line, away from the critical path of casing-running operations on the rig. This is followed by a process to make the final brazed joint. Briefly, the pin of the joint is stabbed and made up to a fraction of the required optimal torque; the filler material already deposited on the threads is melted using heat; and the joint is torqued up to its final makeup torque. This is followed by cooling of the joint before running in hole. It is important to note that virtually any casing connector can be joined with this technology.

Filler-Material Selection on the Basis of Pipe Grade. The type of filler material is determined on the basis of the pipe grade, which, in turn, is determined by the application. To determine the sensitivity of the pipe grade to the effect of heat treatment, a set of simple experiments was carried out.