1、Designation: D 6726 01 (Reapproved 2007)Standard Guide forConducting Borehole Geophysical LoggingElectromagnetic Induction1This standard is issued under the fixed designation D 6726; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is focused on the general procedures neces-sary to conduct electromagnetic-induction, inductio
3、n,electromagnetic-conductivity, or electromagnetic-resistivitylogging (hereafter referred as induction logging) of boreholes,wells, access tubes, caissons, or shafts (hereafter referred asboreholes) as commonly applied to geologic, engineering,ground-water and environmental (hereafter referred as ge
4、o-technical) investigations. Induction logging for minerals orpetroleum applications is excluded.1.2 This guide defines an induction log as a record offormation electrical conductivity or resistivity with depth asmeasured by the induction method in a borehole.1.2.1 Induction logs are treated quantit
5、atively and should beinterpreted with other logs and data whenever possible.1.2.2 Induction logs are commonly used to: (1) delineatelithology; (2) evaluate formation water quality and effectiveporosity, and (3) correlate stratigraphy between boreholes.1.3 This guide is restricted to induction measur
6、ements thatare at a frequency of less than 50 KHz; are non-directional; andaverage formation properties around the circumference of theborehole; which are the most common induction measurementdevices used in geotechnical applications.1.4 This guide provides an overview of induction loggingincluding
7、(1) general procedures; (2) specific documentation;(3) calibration and standardization; and (4) log quality andinterpretation.1.5 To obtain additional information on induction logs seeReferences section in this guide.1.6 This guide is to be used in conjunction with StandardGuide D 5753.1.7 This guid
8、e offers an organized collection of informationor a series of options and does not recommend a specific courseof action. This guide should not be used as a sole criterion forinduction logging and does not replace education, experience,and professional judgement. Induction logging proceduresshould be
9、 adapted to meet the needs of a range of applicationsand stated in general terms so that flexibility or innovation arenot suppressed. Not all aspects of this guide may be applicablein all circumstances. This ASTM standard is not intended torepresent or replace the standard of care by which the adequ
10、acyof a given professional service must be judged withoutconsideration of a projects many unique aspects. The wordstandard in the title of this document means that the documenthas been approved through the ASTM consensus process.1.8 The geotechnical industry uses English or SI units. Theinduction lo
11、g 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 thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practice
12、s and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D 420 Guide to Site Characterization for Engineering De-sign and Construction PurposesD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 5088 Practices for Decontaminatio
13、n of Field EquipmentUsed at Waste SitesD 5608 Practices for Decontamination of Field EquipmentUsed at Low Level Radioactive Waste SitesD 5730 Guide for Site Characterization for EnvironmentalPurposes With Emphasis on Soil, Rock, the Vadose Zoneand Ground WaterD 5753 Guide for Planning and Conducting
14、 Borehole Geo-physical LoggingD 6167 Guide for Conducting Borehole Geophysical Log-ging: Mechanical Caliper1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.01 on Surface and SubsurfaceCharacterization.Current edition appr
15、oved July 1, 2007. Published August 2007. Originallyapproved in 2001. Last previous edition approved in 2001 as D 6727 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
16、er to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 6235 Practice for Expedited Site Characterization ofVadose Zone and Ground Water Contamination at Hazard-ous Waste Contami
17、nated SitesD 6274 Guide for Conducting Borehole Geophysical Log-ging - GammaD 6429 Guide for Selecting Surface Geophysical MethodsD 6431 Guide for Using the Direct Current ResistivityMethod for Subsurface Investigation3. Terminology3.1 DefinitionsDefinitions shall be in accordance withterms and symb
18、ols given in Terminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 accuracyhow close a measured log value ap-proaches true value. It is determined in a controlled environ-ment. A controlled environment represents a homogeneoussample volume with known properties.3.2.2 depth of in
19、vestigationthe radial distance from themeasurement point to a point where the predominant measuredresponse may be considered centered, which is not to beconfused with borehole depth (for example, distance) mea-sured from the surface.3.2.3 measurement resolutionthe minimum change inmeasured value tha
20、t can be detected.3.2.4 repeatabilitythe difference in magnitude of twomeasurements with the same equipment and in the sameenvironment.3.2.5 vertical resolutionthe minimum thickness that canbe separated into distinct units.3.2.6 volume of investigationthe volume that contributes90 percent of the mea
21、sured response. It is determined by acombination of theoretical and empirical modeling. The vol-ume of investigation is non-spherical and has gradationalboundaries.4. Summary of Guide4.1 This guide applies to induction logging and is to be usein conjunction with Guide D 5753.4.2 This guide briefly d
22、escribes the significance and use,apparatus, calibration and standardization, procedures andreports for conducting induction logging.5. Significance and Use5.1 An appropriately developed, documented, and executedguide is essential for the proper collection and application ofinduction logs. This guid
23、e is to be used in conjunction withGuide D 5753.5.2 The benefits of its use include improving: selection ofinduction logging methods and equipment; induction logquality and reliability; and usefulness of the induction log datafor subsequent display and interpretation.5.3 This guide applies to common
24、ly used induction loggingmethods for geotechnical applications.5.4 It is essential that personnel (see Section 8.3.2, GuideD 5753) consult up-to-date textbooks and reports on theinduction technique, application, and interpretation methods.6. Interferences6.1 Most extraneous effects on induction logs
25、 are caused bylogging procedures, instrument problems, borehole conditions,and geologic conditions.6.2 Logging procedures include incorrect range setting,incorrect calibration, and logging too fast.6.3 Instrument problems include electrical leakage and tem-perature drift.6.3.1 Induction probes need
26、to warm up and stabilize withthe borehole environment. Some probes record internal elec-tronic temperature; this temperature record should not beconfused with a borehole fluid temperature log.6.4 Effects of borehole fluid is dependent on probe design,borehole diameter, and borehole-fluid conductivit
27、y. Inductionmeasurements can be made in air-, water-, or mud-filledboreholes. Induction probes are designed to minimize effects ofborehole fluid. Conductivity of borehole fluid will significantlyaffect induction response only in larger diameter boreholes(typically, greater than 8 to 10 in. (20 to 25
28、 cm) diameter).6.4.1 Effects of mud-invasion zone is dependent on probedesign, invasion depth, and mud and formation conductivity.6.4.2 Steel or other conductive material interferes and mayprohibit induction measurements. PVC casing and other non-conductive casing does not affect induction response.
29、 Clayseals and sand/gravel packs may affect induction response inlarger diameter boreholes (typically, greater than 8 to 10 in. (20to 25 cm) diameter).6.5 Geologic Conditions:6.5.1 In high-conductivity formations and ground water, theelectrical conductivity measured by induction is less than thetrue
30、 electrical conductivity due to skin effects. Some probescorrect for skin effect assuming a homogeneous medium.6.5.2 In steeply dipping formations (greater than 60 de-grees), electrical anisotropy affects apparent bed thickness andlocation of bed contacts and corrections need to be applied.6.6 Theor
31、etical and empirical tool response curves andinversion algorithms may be applied to correct for manyinterferences.7. Apparatus7.1 A geophysical logging system has been described in thegeneral guide (Section 6, Guide D 5753).7.2 Induction logs are collected with probes that haveelectromagnetic transm
32、itter and receiver coils (Fig. 1).7.2.1 Transmitter and receiver coils typically are spacedabout 20 in. (50 cm) apart. In deep-induction configurations,coils are spaced at about 40 in (1 m) apart.7.2.2 The transmitter coil emits an electromagnetic signal inthe range of 20 to 40 KHz that induces eddy
33、 currents in themedium surrounding the borehole.7.2.3 The receiver coil senses the primary and secondarymagnetic fields.7.2.4 Strength of the secondary magnetic field is a functionof the electrical conductivity of the surrounding medium.7.2.5 One or more additional coils are used to cancel theprimar
34、y field, reduce sensitivity to the borehole fluid, and focusthe horizontal response.D 6726 01 (2007)27.3 Volume of Investigation and Depth of Investigation ofinduction measurements are dependent on coil configurationand increases with increased spacing between transmitter andreceiver coils.7.3.1 The
35、 Depth of Investigation typically varies from 20 to30 in. (50 to 75 cm) (Fig. 2), but is up to 130 in. (325 cm) indeep-induction configurations.7.3.2 The radial distance from which log response is negli-gible typically varies from 3 to 5 in. (7.5 to 12.5 cm), but is 20in. (50 cm) or more in deep-ind
36、uction configurations.7.3.3 Induction probes used for geotechnical applicationstypically can be logged inside of a 2 in. (5 cm) diametermonitoring well.7.3.4 Dual-induction probes have coil configurations thatmeasure two different depths of investigations including deepinduction and generally are gr
37、eater than 2 in. (5 cm) indiameter.7.4 Vertical Resolution of induction measurements is depen-dent on coil configuration.7.4.1 Vertical Resolution is approximated by dividing thetransmitter-receiver coil spacing by 1.5.7.4.2 Vertical Resolution typically is about 14 in. (35 cm).7.4.3 Vertical Resolu
38、tion is up to 6 feet in deep-inductionconfigurations.7.5 Typical accuracy is within 5 percent at 30 mS/m.7.6 Additional logs may also be run in combination withinduction.7.6.1 Induction probes commonly have the capability tosimultaneously record gamma along with electrical conductiv-ity.7.6.2 Induct
39、ion and gamma logs can be collected in open orboreholes cased with non-conductive materials (PVC, fiber-glass, etc.) that are air, water, or mud filled.7.6.3 Some induction probes may also record magneticsusceptibility simultaneously with the electric conductivitymeasurement. Note induction probes t
40、ypically are not opti-mized for magnetic susceptibility measurements.FIG. 1 Electromagnetic-Induction Logging System (8)FIG. 2 Cumulative Response Versus Radial Distance for a Typical Electromagnetic-Induction Probe Showing Depth of Investigation andRadial Focusing (11)D 6726 01 (2007)37.7 Measureme
41、nt resolution of induction probes is deter-mined by probe design. Measurement resolution is typically0.01 mS/m.7.8 A variety of induction logging equipment available isfor geotechnical investigations. It is not practical to list all ofthe sources of potentially acceptable equipment.8. Calibration an
42、d Standardization of Electromagnetic-Induction Logs8.1 General:8.1.1 National Institute of Standards and Technology(NIST) calibration and standardization procedures do not existfor induction logging.8.1.2 Induction logs can be used in a qualitative (forexample, comparative) or quantitative manner de
43、pending uponthe project objectives.8.1.3 Induction calibration methods and frequency shall besufficient to meet project objectives.8.1.3.1 Calibration and standardization should be performedeach time an induction probe is suspected to be damaged,modified, repaired, and at periodic intervals.8.1.3.2
44、Induction probe calibration is sensitive to the effectsof temperature, humidity, calibration coil position, and conduc-tive material.8.2 Calibration is the process of establishing values forinduction response and is accomplished in free air and withrepresentative physical models. Calibration data va
45、lues relatedto the physical properties are recorded in units (for example,counts per second) that are converted to units of electricalconductivity (mS/m).8.2.1 At least two, and preferably more, values, whichapproximate the anticipated operating range, are needed toestablish a calibration curve (for
46、 example, 10 and 100 mS/m).8.2.2 Typical tolerances for calibration are 5 percent ofmeasured standard.8.2.3 Calibration is done in an area free of conductiveobjects within the Volume of Investigation.8.2.4 Free-air calibration check to approximately zero elec-trical conductivity is accomplished by s
47、uspending the probe inair where humidity is minimal and away from conductivematerial.8.2.5 The physical model typically used to calibrate induc-tion response is a calibration ring.8.2.5.1 A calibration ring is a ring of non-conductive mate-rial (plastic or wood), which has a wire loop with a resista
48、ncethat produces a known response.8.2.5.2 The position of the calibration ring on the probemust be duplicated for accurate calibration. Calibration ringsdesigned not be positioned at the center of the measurementpoint are more sensitive to changes in their position.8.2.6 Calibration also can be esta
49、blished in a body of watersuch as a lake with a known electrical conductivity that is largeenough to be infinite with respect of the Volume of Investiga-tion of the probe.8.2.7 Calibration should be performed when the probetemperature is as close to the borehole temperature as possible.This is most readily performed by recalibrating immediatelyafter logging a borehole.8.3 Standardization is the process of checking loggingresponse to show evidence of repeatability and consistency.8.3.1 Calibration insures standardization.8.3.2 A representative borehole may be used to period
