Simply introduced are the physical & chemical properties, forming conditions, existing models of gas hydrate, and logging responses and evaluation methods for gas hydrate reservoir. The log responses prove that several logs, such as natural gamma ray log, caliper log, density log, neutron log, acoustic log and resistivity log, have obvious responses in gas hydrate reservoir. A combined resistivity-acoustic log is the most effective method for identifying the gas hydrates. The present logging technologies have difficulties in such reservoir assessments. Since gas hydrates easily accumulate in the tundra, and high frequency dielectric log is the best way to tell the hydrate from ice, so it's better to use LWD log. In disperse marine sediments, the wireline log has much poor reliability, therefore, the LWD log may help strengthen the reliability, and to further enhance this reliability, we should improve log resolutions. Porosity of the hydrate-bearing reservoir is higher, so it is hard for core boring. Since there is always hydrate decompositing in the process of core transportation from well head to lab, storage in the core chambers and second core samplings, etc., so, the obtained test data will not be very accurate. At last, the difficulties are pointed out in gas hydrate evaluation based on present logging technologies.%介绍了天然气水合物的物理化学性质、形成条件及赋存模式,以及天然气水合物储层的测井响应特征和测井评价方法.自然伽马、井径、密度、中子、声波和电阻率测井在天然气水合物层段均有明显反应.电阻率与声波测井组合被认为是识别天然气水合物最有效的方法.指出现阶段测井技术对天然气水合物评价存在的困难.水合物容易富集在冻土层,高频介电测井是区分天然气水合物和冰的最好途径,最好使用随钻测井;在松散的海洋沉积环境下电缆测井响应的可信度大大降低;可以通过随钻测井改进和改进测井分辨率使其解释结论更加可靠;天然气水合物储层孔隙度偏大且质地疏松,钻井取心困难;岩心从井口向实验室运输、被放人岩心室以及二次取样和保存过程中都有可能存在天然气水合物分解,造成实验数据不准确.
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