Advanced Deepwater Monitoring System

Abstract

This study investigates new methods to improve deepwater monitoring and addresses installation of advanced sensors on “already deployed” risers, flowlines, trees, and other deepwater devices. A major shortcoming of post installed monitoring systems in subsea is poor coupling between the sensor and structure. This study provided methods to overcome this problem. Both field testing in subsea environments and laboratory testing were performed. Test articles included actual flowline pipe and steel catenary risers up to twenty-four inches in diameter. A monitoring device resulting from this study can be installed in-situ on underwater structures and could enhance productivity and improve safety of offshore operations. This paper details the test results to determine coupling methods for attaching fiber optic sensor systems to deepwater structures that have already been deployed. Subsea attachment methods were evaluated in a forty foot deep pool by divers. Afterword, structural testing was conducted on the systems at the NASA Johnson Space Center. Additionally a 7,000 foot deep sensor station was attached to a flowline with the aid of a remote operated vehicle. Various sensor to pipe coupling methods were tested to measure tensile load, shear strength and coupling capability. Several adhesive bonding methods in a subsea environment were investigated and subsea testing yielded exceptionally good results. Tensile and shear properties of subsea application were approximately 80 percent of those values obtained in dry conditions. Additionally, a carbide alloy coating was found to increase the shear strength of metal to metal clamping interface by up to 46 percent. This study provides valuable data for assessing the feasibility of developing the next generation fiber optic sensor system that could be retrofitted onto existing subsea pipeline structures.