祁连山冻土区DK-1钻孔天然气水合物测井响应特征和评价

    Well logging characteristics and evaluation of hydrates in Qilian Mountain permafrost

    • 摘要: 祁连山冻土区天然气水合物科学钻探工程中采用电缆测井识别水合物储层,使用了三侧向、声波速度、自然伽马、长源距伽马伽马、井温、井径、井斜7种测井仪器,所获参数有利于确定天然气水合物的赋存位置。根据DK-1钻孔中获得水合物样品层段的测井曲线总结出水合物测井响应的特征,并参考国外的相关资料,对DK-1地层的孔隙度和天然气水合物饱和度进行了初步评价。结果表明,电阻率方法求出的地层孔隙度与岩心分析值较为接近,而用标准阿尔奇方程和修正的阿尔奇方程计算出的天然气水合物的饱和度值相差较大。因此,尚需对水合物岩心进行深入的分析测试,建立适当的岩石物理模型,来指导中国天然气水合物的测井评价。

       

      Abstract: Wireline logging was employed to confirm gas hydrate bearing sediments in the Scientific Drilling Project of Gas Hydrate in Qilian Mountain Permafrost. There were seven instruments including resistivity, sonic, natural gamma, density, temperature caliper and inclination logging tools in this project. The parameters acquired from the well logs are important in determining the position of gas hydrate in the Qilian Mountain permafrost. Referring to the data abroad, the authors used log data from drillhole DK-1 to investigate physical properties of gas hydrate and preliminarily estimate the formation porosity and in-situ gas hydrate saturations. The results show that the porosity derived from resistivity agrees with that from core analysis, while in-situ gas hydrate saturations estimated from Standard Archie and Modified Archie equation are different. Therefore, the gas hydrate sample should be further studied so as to develop an appropriate rock-physical model which can guide the future evaluation of gas hydrate.

       

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