Research And Development Of In-situ Monitoring System For Methane Sensor Based On Seafloor Observation Network

Natural gas hydrate is an ice crystal compound composed of water and natural gas,which main component is methane(CH₄).Methane is an important greenhouse gas,which has a 21 fold effect on greenhouse gases co MPared with carbon dioxide.Researches show that more than 90%of the natural gas hydrate in the world distributes in the ocean,and the decomposition of gas hydrate is the main source of methane in sea water,thus,it's very important for the exploration and development of gas hydrate to detect the abnormal changes of methane concentration in sea water.The submarine observation network is considered to be the"third platform"for observing the ocean,which can realize all-weather,comprehensive and long-term continuous real-time observation of marine internal processes and relationship.Therefore,it is urgent currently and also has practical significance for marine environment monitoring,new energy exploration and development to research and develop marine methane in-situ detection system based on seafloor observation network.This research is based on the sub project entitled“series of high-precision detection of deep-sea methane concentration sensor system”which belongs to the National High Technology Research and Development Program 863 project entitled“The new type of marine chemical sensor for long term observation network of ocean bottom”.An instrument for real-time,long-term and continuous observation of methane concentration in seawater is introduced in this paper.Based on the investigation of the status of the submarine observation network and the methane sensor dissolved in seawater and according to the design principle and task requirements of the methane sensor,the internal structure of the sensor is designed as follows:Buck steady flow system,gas-liquid separation system,gaseous hydrocarbon detection system,signal acquisition system and pressurization system,meanwhile,a drainage system of ultra-high pressure liquid pump,liquid storage tank and probe is designed to ensure the smooth implementation of the sensor function.“An adjustable temperature and pressure solution preparation device”was developed to simulate the properties and supply of marine fluid in the deep sea environment,which provides technical support for the establishment of experimental environment for the development of instruments.The important contribution of this paper:The design of methane sensor control system was accomplished,the sensor work flow was optimized and the parameter selection was accomplished through the experimental study of the marine conditions.The in situ test and connection test of the offshore instruments were accomplished.The data of the dissolved methane in sea water was successfully obtained.The rationality and scientificity of the design system was verified.According to the problems occurring during the experiment and the test results,some suggestions for the subsequent research and development of the instrument were put forward.