1、Designation: D6726 01 (Reapproved 2007)D6726 15Standard Guide forConducting Borehole Geophysical LoggingElectromagnetic Induction1This standard is issued under the fixed designation D6726; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This guide is focused on the general procedures necessary to conduct electromagnetic-inductio
3、n, 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 andenvironmental (hereafter re
4、ferred as geotechnical) investigations.explorations. Induction logging for minerals or petroleumapplications is excluded.1.2 This guide defines an induction log as a record of formation electrical conductivity or resistivity with depth as measuredby the induction method in a borehole.1.2.1 Induction
5、 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 res
6、tricted to induction measurements that are at a frequency of less than 50 KHz; are non-directional; andaverage formation properties around the circumference of the borehole; which are the most common induction measurementdevices used in geotechnical applications.1.4 This guide provides an overview o
7、f 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 S
8、tandard Guide D5753.1.6 This guide offers an organized collection of information or a series of options and does not recommend a specific courseof action. This guide should not be used as a sole criterion for induction logging and does not replace education, experience, andprofessional judgement.jud
9、gment. Induction logging procedures should be adapted to meet the needs of a range of applications andstated in general terms so that flexibility or innovation are not suppressed. Not all aspects of this guide may be applicable in allcircumstances. This ASTM standard is not intended to represent or
10、replace the standard of care by which the adequacy of a givenprofessional service must be judged without consideration of a projects many unique aspects. The word standard in the title ofthis document means that the document has been approved through the ASTM consensus process.1.7 UnitsThe geotechni
11、cal industry uses English or SI units. The induction log is typically recorded in millisiemens per meter(mS/m) or millimhos per meter (mmhos/m).values stated in either inch-pound units or SI units given in brackets are to beregarded separately as standard. The values stated in each system may not be
12、 exact equivalents; therefore, each system shall beuse independently of the other. Combining values from the two systems may result in non-conformance with the standard. Add,if appropriate, “Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard.”
13、1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatoryrequirements prior to use.1 This guide is
14、under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.01 on Surface and SubsurfaceCharacterization.Current edition approved July 1, 2007Dec. 1, 2015. Published August 2007January 2016. Originally approved in 2001. Last previous edition app
15、roved in 20012007 asD6727 01.D6727 01(2007). DOI: 10.1520/D6726-01R07.10.1520/D6726-15.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to
16、 adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright
17、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2D420 Guide to Site Characterization for Engineering Design and Construction Purposes (Withdrawn 2011)3D653 Terminology Relating to Soil, Rock, and Contai
18、ned FluidsD5088 Practice for Decontamination of Field Equipment Used at Waste SitesD5608 Practices for Decontamination of Field Equipment Used at Low Level Radioactive Waste SitesD5730 Guide for Site Characterization for Environmental Purposes With Emphasis on Soil, Rock, the Vadose Zone andGroundwa
19、ter (Withdrawn 2013)3D5753 Guide for Planning and Conducting Borehole Geophysical LoggingD6167 Guide for Conducting Borehole Geophysical Logging: Mechanical CaliperD6235 Practice for Expedited Site Characterization of Vadose Zone and Groundwater Contamination at Hazardous WasteContaminated SitesD627
20、4 Guide for Conducting Borehole Geophysical Logging - GammaD6429 Guide for Selecting Surface Geophysical MethodsD6431 Guide for Using the Direct Current Resistivity Method for Subsurface Investigation3. Terminology3.1 DefinitionsDefinitions: Definitions shall be in accordance with terms and symbols
21、given in Terminology D653.3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 accuracyhow close a measured log value approaches true value. It is determined in a controlled environment. Acontrolled envir
22、onment represents a homogeneous sample volume with known properties.3.2.1 depth of investigationexploration, nin geophysics, the radial distance from the measurement point to a point wherethe predominant measured response may be considered centered, which is not centered (not to be confused with bor
23、ehole depth(for example, distance) measured from the surface.the depth below the surface).3.2.3 measurement resolutionthe minimum change in measured value that can be detected.3.2.4 repeatabilitythe difference in magnitude of two measurements with the same equipment and in the same environment.3.2.2
24、 vertical resolutionresolution, nthe minimum thickness that can be separated into distinct units.3.2.3 volume of investigationexploration, nthe volumein geophysics, a volume, which is non-spherical and has gradationboundaries, that contributes 90 percent of the measured response. Itresponse, and is
25、determined by a combination of theoreticaland empirical modeling. The volume of investigation is non-spherical and has gradational boundaries.4. Summary of Guide4.1 This guide applies to induction logging and is to be use in conjunction with Guide logging.D5753.4.2 This guide briefly describes the s
26、ignificance and use, apparatus, calibration and standardization, procedures and reports forconducting induction logging.5. Significance and Use5.1 An appropriately developed, documented, and executed guide is essential for the proper collection and application ofinduction logs. This guide is to be u
27、sed in conjunction with Guide D5753.5.2 The benefits of its use include improving: selection of induction logging methods and equipment; induction log quality andreliability; and usefulness of the induction log data for subsequent display and interpretation.5.3 This guide applies to commonly used in
28、duction logging methods for geotechnical applications.5.4 It is essential that personnel (see Section 8.3.2, Guide D5753) consult up-to-date textbooks and reports on the inductiontechnique, application, and interpretation methods.6. Interferences6.1 Most extraneous effects on induction logs are caus
29、ed by logging procedures, instrument problems, borehole conditions, andgeologic conditions.6.2 Logging procedures include incorrect range setting, incorrect calibration, and logging too fast.6.3 Instrument problems include electrical leakage and temperature drift.2 For referencedASTM standards, visi
30、t theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.D6726 1526.3.1 Induction probes need to warm up and stabilize with the borehole environment. Some
31、 probes record internal electronictemperature; this temperature record should not be confused with a borehole fluid temperature log.6.4 Effects of borehole fluid is dependent on probe design, borehole diameter, and borehole-fluid conductivity. Inductionmeasurements can be made in air-, water-, or mu
32、d-filled boreholes. Induction probes are designed to minimize effects of boreholefluid. Conductivity of borehole fluid will significantly affect induction response only in larger diameter boreholes (typically, greaterthan 8 to 10 in. (2020 to 25 cm)cm diameter).6.4.1 Effects of mud-invasion zone is
33、dependent on probe design, invasion depth, and mud and formation conductivity.6.4.2 Steel or other conductive material interferes and may prohibit induction measurements. PVC casing and othernon-conductive casing does not affect induction response. Clay seals and sand/gravel packs may affect inducti
34、on response in largerdiameter boreholes (typically, greater than 8 to 10 in. (2020 to 25 cm)cm diameter).6.5 Geologic Conditions:6.5.1 In high-conductivity formations and groundwater, the electrical conductivity measured by induction is less than the trueelectrical conductivity due to skin effects.
35、Some probes correct for skin effect assuming a homogeneous medium.6.5.2 In steeply dipping formations (greater than 60 degrees), electrical anisotropy affects apparent bed thickness and locationof bed contacts and corrections need to be applied.6.6 Theoretical and empirical tool response curves and
36、inversion algorithms may be applied to correct for many interferences.7. Apparatus7.1 A geophysical logging system has been described in the general guide (Section 6, Guide D5753).7.2 Induction logs are collected with probes that have electromagnetic transmitter and receiver coils (Fig. 1).7.2.1 Tra
37、nsmitter and receiver coils typically are spaced about 20 in. (50 cm)0.5 m apart. In deep-induction configurations,coils are spaced at about 40 in (1 m)1 m apart.7.2.2 The transmitter coil emits an electromagnetic signal in the range of 20 to 40 KHzkHz that induces eddy currents in themedium surroun
38、ding the borehole.7.2.3 The receiver coil senses the primary and secondary magnetic fields.7.2.4 Strength of the secondary magnetic field is a function of the electrical conductivity of the surrounding medium.7.2.5 One or more additional coils are used to cancel the primary field, reduce sensitivity
39、 to the borehole fluid, and focus thehorizontal response.7.3 Volume of InvestigationExploration and Depth of InvestigationExploration of induction measurements are dependent oncoil configuration and increases with increased spacing between transmitter and receiver coils.7.3.1 The Depth of Investigat
40、ionExploration typically varies from 20 to 30 in. (5050 to 75 cm)cm (Fig. 2), but is up to 130in. (325 cm)325 cm in deep-induction configurations.7.3.2 The radial distance from which log response is negligible typically varies from 3 to 5 in. (7.57.5 to 12.5 cm),cm, butis 20 in. (50 cm)50 cm or more
41、 in deep-induction configurations.7.3.3 Induction probes used for geotechnical applications typically can be logged inside of a 2 in. (5 cm)5 cm diametermonitoring well.7.3.4 Dual-induction probes have coil configurations that measure two different depths of investigationsexplorations includingdeep
42、induction and generally are greater than 2 in. (5 cm)5 cm in diameter.7.4 Vertical Resolution of induction measurements is dependent on coil configuration.FIG. 1 Electromagnetic-Induction Logging System (1)D6726 1537.4.1 Vertical Resolution is approximated by dividing the transmitter-receiver coil s
43、pacing by 1.5.7.4.2 Vertical Resolution typically is about 14 in. (35 cm).35 cm.7.4.3 Vertical Resolution is up to 6 feet ft 1.8 m in deep-induction configurations.7.5 Typical accuracy is within 5 percent at 30 mS/m.7.6 Additional logs may also be run in combination with induction.7.6.1 Induction pr
44、obes commonly have the capability to simultaneously record gamma along with electrical conductivity.7.6.2 Induction and gamma logs can be collected in open or boreholes cased with non-conductive materials (PVC, fiberglass,etc.) that are air, water, or mud filled.7.6.3 Some induction probes may also
45、record magnetic susceptibility simultaneously with the electric conductivity measure-ment. Note induction probes typically are not optimized for magnetic susceptibility measurements.7.7 Measurement resolution of induction probes is determined by probe design. Measurement resolution is typically 0.01
46、 mS/m.7.8 A variety of induction logging equipment available is for geotechnical investigations.explorations. It is not practical to listall of the sources of potentially acceptable equipment.8. Calibration and Standardization of Electromagnetic-Induction Logs8.1 General:8.1.1 National Institute of
47、Standards and Technology (NIST) calibration and standardization procedures do not exist forinduction logging.8.1.2 Induction logs can be used in a qualitative (for example, comparative) or quantitative manner depending upon the projectobjectives.8.1.3 Induction calibration methods and frequency shal
48、l be sufficient to meet project objectives.8.1.3.1 Calibration and standardization should be performed each time an induction probe is suspected to be damaged, modified,repaired, and at periodic intervals.8.1.3.2 Induction probe calibration is sensitive to the effects of temperature, humidity, calib
49、ration coil position, and conductivematerial.8.2 Calibration is the process of establishing values for induction response and is accomplished in free air and withrepresentative physical models. Calibration data values related to the physical properties are recorded in units (for example, countsper second) that are converted to units of electrical conductivity (mS/m).mS/m.8.2.1 At least two, and preferably more, values, which approximate the anticipated operating range, are needed to establish acalibration curve (for example, 10 and 100 mS
