Well logging characteristics and evaluation of hydrates in Qilian Mountain permafrost

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.