Fiber-Based Methane Leak Detection

Abstract Fiber-based Methane Leak Detection System The current focus in the post-Macondo era is the need to make the offshore work environment safe. The use of a fiber-based backbone to perform a number of functions in an installation with the potential of an explosive atmosphere has significant potential. Currently the novel fiber backbone has the capability to provide three basic functions: area and equipment lighting, distributed remote temperature sensing, and distributed remote methane sensing. The application of fiber optics for lighting and distributed sensing is a mature concept. It is the use of fiber optics for methane detection that is novel. Methane sensing utilizing discrete passive sensors connected to a central sensing unit with fiber optic cable. The system utilizes a low power (10mW) diode laser in conjunction with a distributed fiber network and a series of ruggedized sensor modules. It is largely unaffected by common environmental conditions which can cause erroneous readings with many other sensor types including high humidity, anaerobic conditions, and the presence of other non-target gases. The system is tolerant of dust contamination, and fully functioning at signal losses of up to 90%. It can be configured as a distributed network with hundreds of sensing points at distances of up to 20 km from a central control unit. Methane levels from 0.5 to 100% can be accurately measured. Standard communication grade fiber cable is utilized. Unlike conventional methane detection systems currently employed, this system does not require calibration at the remote sensor. Various alarm schemes can be configured to look for rising methane levels, over-limit conditions, as well as breaks in the sensing fiber. This paper describes the concepts and provides examples of real-world implementations of how this technology can provide for safe offshore working conditions.