T23 Geologic Emissions of Methane from Lands and Seafloor: Mud Volcanoes and Observing System (Posters)

GMM - A GAS MONITORING MODULE FOR SEABED METHANE LEAKAGE

Paper number: T23-5
Program: Technical Sessions
Time: 1:30 PM – 4:30 PM

Authors

Abstract

Methane monitoring in marine environments is an urgent task demanded by the scientific community in the framework of geohazard, biological and global change studies. In this respect a new seafloor lander module (GMM - Gas Monitoring Module) has been developed by the European Commission ASSEM project (Array of Sensors for long term SEabed Monitoring of geohazards) for continuous and long-term measurements of methane concentration in seawater at the benthic boundary layer. The module is designed to host a series of sensors controlled and managed by a data acquisition and control system capable of performing first-level data quality checks. The prototype includes semi-conductor methane sensors and a CTD for temperature, salinity, pressure recording, as well as interfaces available for further sensors. The electronics can perform a series of tasks including: data acquisition from all scientific packages and status sensors, preparation and continuous update of a periodic (e.g. hourly) data message, ready to be transmitted via serial link on request, management of the sensors (switch on/off of individual sensors according to command from operator; event detection), reception and management of commands from external units (data request, system reconfiguration, restart, etc.), monitor internal status parameters and external power supply, back-up of data in internal memory. The methane sensor (METS by Capsum) is an improved version of a commercial product used for short-term deployment such as profiling. It uses a semi-conductor as sensing element, integrated in a small gas volume in the sensor-head. Protection against the outside water and pressure is given by a special membrane. The improved version for GMM addresses long-term operativity, increased operation depth and increased sensitivity. A series of tests showed the improved METS performance. GMM can be linked to submarine cables for real-time data transmission to onshore operators. The system is suitable to monitor, for long periods, natural gas emission from seafloor or leakages from pipelines and boreholes.