For recent years gas hydrate has discovered in northern part of Southern ocean and in frozen zone of southern fringe of Qilian mountain ,in Qinghai province, Tianjun county in China. This new energy source will play an important role for adjusting energy resources structures and relaxing the energy resources tension of China. In September and October 2011 the scientists of IET CDA twice made experimental exploitation in the frozen zone. Experimental exploitation lasted 11 hours, total volume of obtained gas was more than 85 cubic meters. The obtained gas was methane. That means, that China has discovered gas hydrate in the ocean and land. However the security of exploitation of the gas hydrate is a serious problem in the world. The casing tube column state is an important part of the problem. The Institute of Well Geophysical Research, Russia Federation, has developed a small diameter electro magnetic detector ЭМДС-ТМ-42TC, with help of which the technical state of casing tube column can be controlled and measured. The detector has been used in many countries of the world and excellent results obtained.