| The natural gas hydrate formats and exists in high-pressure and low-temperature environment. For the particularity of the environment, there have been difficulties in gas hydrate exploration.There are two kinds of ideas for gas hydrates sampler design at home and abroud, one is mainly holding pressure and accessorial preserving heat. The other is mainly preserving heat and accessorial holding pressure or not. Hydrate samplers abroud based largely on pressure holding, and this kind of sampler is mainly used in marine sedimentary strata of natural gas hydrate. In recent years, Jilin University gives out the freezing idea for the gas hadryte sampler design by the research and analysis to the temperature-pressure characteristic of the gas hadryte. Then this idea was put into the development of the gas hadryte sampler.The paper uses freezing idea of freezing the sample in the hole. The way of freezing sampling is combineed with the wire-line coring technique. The sampler uses refrigerant to freeze the hadryte core to a certain temperature(-20℃). Then use wire-line coring method to bring the core out of the hole quickly. Compared with dill-lift coring, wire-line coring technique is faster, which can prevent the decompositing of hydrate core in the process of lifting.The paper refers to the existing ordinary wire-line coring samplers. Then design the freezing and wire-line coring sampler and its technical parameters. The sampler has not only the basic structure of the ordinary wire-line coring sampler, but also the internal and external spline institutions, control mechanism, refrigeration preservation organizations and frozen institutions. Then the agencies of the sampler were designed and the technical parameters for the entire drilling tool were confirmed. That provides reference for the design and processing of the sampler.The preservation of the refrigerant is an important prerequisite for the sampler to achive its frozen fuction. How to effectively save the refrigerant is the focus of this paper. The existing refrigerant-dry ice and liquid nitrogen are studied and compared in the paper. Relevant refrigerant saving style is put forward for their different physical properties. For dry ice, heat insulating material is used to save cold. By the study and contrast to the commonly used insulation material, the best performance insulating material- polyurethane which is widely used is chosen to save dry ice. The paper designs the cold saving structure, and calculate the cold insulation thickness in heat transfer method. For liquid nitrogen, Because of its ultra-low temperature properties which exceed the range of existing insulation materials, vacuum insulation is adopted to save this refrident. The paper reference to currently available low-temperature medium container, design the basic structure of the cold saving container, applicable to the sampler. Then calculate the cold loss of the container. At last, take experiments to verify the cooling measures for the dry ice and liquid nitrogen.Then, a frozen gas hydrate indoor test bed is established, which uses sand samples as the simulation core. Sand sample is frozen respectively in dry ice and liquid nitrogen. The results showed that the dry ice freezing rate to the simulation core (0.52℃/ min) is far less than the liquid nitrogen (9.5℃/ min). At the same time, r the heating rate of the core frozen by dry ice (0.25℃/ min ) is also less than the liquid nitrogen (0.8℃/ min). The paper also simulated temperature changes of the simulaton core by finite element method. Then draw the temperature curve of core and the temperature distribution in cross section at the lowest point of the temperature.The simulation results are compared with the experimental results .Then the right refrigent and its freezing style which is more suitable for the sampler is got. After analysis and comparison, using liquid nitrogen as a refrigerant gives a more significantly larger cooling rate than using dry ice. That mesns using liquid nitrogen as a refrigerant has a better effect.
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