Method of measurement Methane hydrate using Acoustic Doppler Current Profiler

近年来，由于石油和煤炭等有限资源的枯竭，甲烷水合物（MH）引起了人们的广泛关注。与石油和煤相比，MH产生的二氧化碳和氮氧化物非常少。MH的这种行为意味着MH在空气污染和地球变暖等环境问题方面比石油和煤炭具有极其上级的优势，另一方面，人们也非常担心MH的开发会破坏底栖生态系统。同时，还应预先评估开发对生态系统的影响和风险.因此，测量MH和/或甲烷羽流的井喷是非常重要的。本文提出了一种利用声学多普勒海流剖面仪（ADCP）测量深海MH深度剖面的新方法。该测量方法将超声波在水下的传播视为反问题，利用超声波在水下的传播模型测量金属基片的深度分布。由于ADCP可以获得三维速度，因此该方法适用于深海监测，以了解MH动力学。

Recently, Methane Hydrate(MH) has attracted much attention because of depletion of a finite resource such as oil and coal. The generation of carbon dioxide and the oxide of nitrogen by MH are very little compared with oil and coal. This behavior of MH means that the MH is extremely superior to oil and coal in terms of environmental problem such as air pollution and earth warming.On the other hand, there is also great fear that the development of MH damages the benthic ecosystem. We should also assess the influence and risk of ecosystem by the development in advance. From these reasons, it is very important to measure the blowout of MH and/or methane plume. However, very few studies have been reported on measurement of MH in deep-sea area.In this study, the author proposed a new measurement method of MH depth profiles with Acoustic Doppler Current Profilers(ADCP). In this measurement method, the propagation of ultrasonic waves was regarded as inverse problem, and the depth profile of MH can be measured by model of propagation of ultrasonic underwater. Since ADCP can be obtained the three-dimensional velocity, the present method is suitable for monitoring in order to understand MH dynamics under deep sea.