ASTM D6726-01(2007)

An appropriately developed, documented, and executed guide is essential for the proper collection and application of induction logs. This guide is to be used in conjunction with Guide D5753.

The benefits of its use include improving: selection of induction logging methods and equipment; induction log quality and reliability; and usefulness of the induction log data for subsequent display and interpretation.

This guide applies to commonly used induction logging methods for geotechnical applications.

It is essential that personnel (see Section 8.3.2, Guide D5753) consult up-to-date textbooks and reports on the induction technique, application, and interpretation methods.

1.1 This guide is focused on the general procedures necessary to conduct electromagnetic-induction, induction, electromagnetic-conductivity, or electromagnetic-resistivity logging (hereafter referred as induction logging) of boreholes, wells, access tubes, caissons, or shafts (hereafter referred as boreholes) as commonly applied to geologic, engineering, groundwater and environmental (hereafter referred as geotechnical) investigations. Induction logging for minerals or petroleum applications is excluded.

1.2 This guide defines an induction log as a record of formation electrical conductivity or resistivity with depth as measured by the induction method in a borehole.

1.2.1 Induction logs are treated quantitatively and should be interpreted with other logs and data whenever possible.

1.2.2 Induction logs are commonly used to: (1) delineate lithology; (2) evaluate formation water quality and effective porosity, and (3) correlate stratigraphy between boreholes.

1.3 This guide is restricted to induction measurements that are at a frequency of less than 50 KHz; are non-directional; and average formation properties around the circumference of the borehole; which are the most common induction measurement devices used in geotechnical applications.

1.4 This guide provides an overview of induction logging including (1) general procedures; (2) specific documentation; (3) calibration and standardization; and (4) log quality and interpretation.

1.5 To obtain additional information on induction logs see References section in this guide.

1.6 This guide is to be used in conjunction with Standard Guide D5753.

1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide should not be used as a sole criterion for induction logging and does not replace education, experience, and professional judgement. Induction logging procedures should be adapted to meet the needs of a range of applications and stated in general terms so that flexibility or innovation are not suppressed. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged without consideration of a project's many unique aspects. The word standard in the title of this document means that the document has been approved through the ASTM consensus process.

1.8 The geotechnical industry uses English or SI units. The induction log is typically recorded in millisiemens per meter (mS/m) or millimhos per meter (mmhos/m).

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.