Innovative Methods for Methane Leakage Monitoring Near Oil and Gas Installations

摘要

In recent years, there has been an increased focus on environmental issues near oil and gas production sitesrnand pipelines. The trend is likely to continue as future oil and gas production is commencing inrnenvironmentally vulnerable areas, and farther north near the polar ice cap. The exploration in more remoternareas implies that online in situ monitoring has great advantages over expedition based monitoring.rnThe Norwegian Geotechnical Institute (NGI) is an independent research and consultancy foundationrnhaving over 40 years of worldwide offshore instrumentation experience. NGI has recently launched arnresearch initiative to develop new methods for in situ and on line environmental monitoring offshore. Inrn2012, NGI designed and installed an integrated environmental monitoring system for subsea leakagerndetection. It was installed on the seabed beneath an operating oil and gas platform in the North Sea. Werngive here an overview of the instrumentation system and the motivation for the different design choices.rnThe system is an example of an integrated monitoring system, where different types of sensors complementrneach other and gives a more thorough understanding of methane transport at the site of interest. Afterrninstallation, NGI has analyzed monitoring data and provided decision support to operator personnel.rnNearly two years of production site data collection represents a unique data set that enables a comprehensivernanalysis of methane transport.rnFrom the operator side, the motivation for environmental monitoring usually arises from the need tornanswer clearly defined questions such as ‘Is there a gas leakage in the production system? Where is it?rnHow large is the leakage?’ The leakage detection system is expected to answer these questions,rnpreferrably in an unambiguous manner. However, natural gas can be released to the water phase fromrnseveral sources e.g. organic matter on the seabed. If the leakage detection monitoring data shall berninterpreted in a control room that operates with alarm states, these sources of background noise must bernidentified and separated from a real leak situation. We look at which circumstances to be aware of andrnhow to maximize the operational value of a leakage detection system.