Research On Key Technologies Of High-precision Detection Of Dissolved Methane Sensor Based On Seafloor Observation

The distribution of dissolved methane concentration in sea water is caused by biochemical process,seepage and diffusion of overlying petroleum resources and dissociation of gas hydrate.Dissolved methane in sea water not only plays an important role in the global climate and marine environment change,but also is one of the effective bases for finding the gas hydrate zone.The traditional method of fluid geochemistry can not realize in-situ and real-time monitoring of dissolved methane in seawater.At present,dissolved methane sensor technology has developed toward in-situ,real-time,efficient and continuous testing methods and directions in the international marine investigation and hydrate resource exploration.In this paper,the research work of high-precision detection of dissolved methane sensor based on seafloor observation is carried out from the aspects of technology design,system composition,working principle,relevant experiments and sea trials,and the main contents are as follows:(1)Starting from the research background and significance,the traditional methods of fluid geochemistry and in-situ detection of dissolved methane in seawater are systematically summarized.On this basis,the overall framework and principle design of the in-situ high-precision methane sensor system for dissolved methane are completed.(2)Research and design process of this system are elaborated in detail,which including the structure design and layout of the compressive cabin,the depressurization-stabilization and circulation of seawater,gas-liquid separation and quantitative injection,the technology of gas hydrocarbon detection,and the power supply and integrated control of the system.(3)The experimental research on the developed system were carried out,including its adaptability of the working environment,stability and reliability of the test performance,as well as the correction of the test data.(4)After the development of methane sensor,we carried out two sea trials in Qingdao and a network connection test in Hainan,the study validates the feasibility and effectiveness of the method,the scientific and rational design of the system,and the stability and reliability of performance.Dissolved methane concentration data of the Yellow Sea and the South China sea have been successfully obtained.Finally,this paper summarizes the research work,and puts forward some suggestions to improve the system function.