| Gas hydrate, which is formed by some water molecules and natural gas molecules under the low temperature and high pressure (normally 0℃,10MPa), is a new type of substituted energy with the traits of high energy density, large reserves and wide-ranging distribution. The research of gas hydrate becomes the hotspot of the development of the geosciences and the energy industry of the present age. The research is involved with many fields, such as the exploration of a new type of energy, greenhouse effect, global carbon cycle, climatic change, ancient ocean, the ocean geological calamity, oil gas transportation, the blockage in the pipeline, the renewal of ship energy and military defense, and may also have the profound influence on the development of geology, environmental sciences and the energy industry.The technology of drilling in the sediments full of gas hydrate is a critical problem for the exploration and exploitation of it. When the bit is drilling the sediments full of gas hydrate, the stress of the wall bore in the hydrate deposits and the stratum at the bottom of the well is released, and the pressure of the strata is reduced. At the same time, great heat energy is produced by the bit cutting rocks and the friction between drilling tools and the well bore, and there is also a problem whether the temperature of the flushing media is controlled well, which may make the temperature in the well becoming higher and then cause the hydrate breakdown. The hydrate breakdown endangers the quality of the drilling, the life of the equipments and the protection of the environment. So it is very important to control the temperature and the pressure in the well, which can ensure the normal drilling, ascertain the reasonable drilling rules, avoid accidents and enhance the social and economic benefits of drilling.For it is difficult to continuously measure the temperature in the well by the actual measurement, simulating the distribution of the temperature in the well by the appropriate models becomes the main approach to determine it. Till now, many researches about this have been done and some models have been set up. Although these models are simplified more or less in some aspects, which limit the degree of the accurateness and the scope of application, they establish the foundation for the further development of the numerical heat transfer.The paper is based on the general project of NSFC, "The study of thermo-pressure characteristics in gas hydrates formation drilling". After a part of the physical, chemical and mechanical properties and the lab results in existence have been studied, the model used to determine the distribution of temperature in the well is set up by the control-volume integration method and the direct formula solution, and then their adaptabilities are discussed. For the control-volume integration method, the discretization method of it is discussed and the coherentmethods used by the numerical calculation are brought out. The solution to the binomial equation with the constant coefficients and the non-linearity, which is attained through the direct formula solution, is emphasized particularly on during the discussion of it. Then the integration invariables are determined by boundary conditions, and the program is worked out to deal with the five different examples, and the curves of the distribution of temperature in the well are drawn. The main content of the paper as follows:In the first chapter, the traits and the research significance of the gas hydrate and the aim and significance of the project are introduced. Then the research status in quo of the gas hydrate and the subject matter are narrated. At the end, the problem to be solved and the approach of research are put forward.In the second chapter, the physical and chemical properties of the gas hydrate are described, including the structure, the components, the inter-solubility between components and the conditions forming it.In the third chapter, the common steps of setting up the mathematical model and the...
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