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Description

This report is a collection of information on the interpretation of well logs and borehole geophysical surveys in permafrost. The body of the report is preceded by an executive summary that gives the highlights of the report in condensed form. The introductory chapter contains background information that is fundamental to the understanding of well log applications in permafrost, including definitions and descriptions of well logs, permafrost, and related terms, and illustrations showing the extent of permafrost in Alaska. Chapter 2 presents information on physical properties of permafrost that relate to well log interpretation, including porosity and pore-filling media (water, ice and air), and their effects on thermal properties, electrical properties and acoustic properties. Chapters 3-8 describe the following types of well logs in detail, including measurement principles and methods, procedures for calibration and interpretation, and identification of special problems related to permafrost: thermal logs, electric logs, sonic logs, nuclear logs, magnetic logs, and miscellaneous (caliper and drilling) logs. Chapter 9 gives information on three types of borehole geophysical surveys, electrical resistivity, seismic velocity, and borehole gravity, with emphasis on the increased depth of investigation afforded by these surveys as compared with well logs. Chapter 10 described a number of specific applications, including the identification of lithology in permafrost, characterization of the thermal regime and the thermal properties of permafrost, petroleum exploration and production, mining applications, and geotechnical applications. A concluding chapter summarizes the information contained in the body of the report and includes a table that gives an overview of the relative value of various borehole geophysical measurements that can be used for delineating and characterizing permafrost. Conclusions of the report are that a number of standard borehole measurement techniques have been tried and proven in permafrost and can be used effectively to delineate and characterize earth material penetrated by the borehole. However, there are several well logging techniques that have special potential for detecting permafrost that have not been tested: dielectric constant, sonic waveform, televiewer, and nuclear magnetic resonance. Borehole electrical and seismic surveys have potential for detecting permafrost at large distances from the borehole, and these techniques need further development and refinement to take full advantage of their capability.

Publication Date

12-17-1985

Keywords

Geophysical well logging, Permafrost, Thermal properties, Alaska

Handle

http://hdl.handle.net/11122/15349

Interpretation of geophysical well logs in permafrost

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