ISO/TR 14685:2001
(Main)Hydrometric determinations — Geophysical logging of boreholes for hydrogeological purposes — Considerations and guidelines for making measurements
Hydrometric determinations — Geophysical logging of boreholes for hydrogeological purposes — Considerations and guidelines for making measurements
This Technical Report is a summary of best practice for those involved in geophysical borehole logging for hydrogeological purposes. It describes the factors that need to be considered and the measurements that are required to be made when logging boreholes. There can, however, be no definite "standard" logging procedure because of great diversity of objectives, ground-water conditions and available technology. Geophysical logging of boreholes is an evolving science, continually adopting new and different techniques. Every application poses a range of problems and is likely to require a particular set of logs to gain maximum information. This Technical Report therefore provides information on field practice with the objective of how variations in measured parameters may be useful to take account of particular local conditions. It deals with the usual types of logging carried out for delineation of aquifer boundaries; mapping aquifer geometry; assessing the chemical quality and quantity of ground water; water-supply purposes; landfill investigations and contamination studies; borehole construction and conditions; and subsurface lithological information. Applications not specifically considered in this Technical Report include mineral and hydrocarbon evaluation and geotechnical and structural engineering investigations. However, this Technical Report may be a source of general information for any borehole geophysical logging effort. NOTE Interpretation of the data collected during logging is referred to in this Technical Report only in a general way. For full details of the analysis and interpretation of geophysical logs, reference should be made to specialized texts. Examples of such texts are included in the Bibliography.
Déterminations hydrométriques — Répertoriage géophysique des trous de sonde pour des besoins hydrogéologiques — Considérations et lignes directrices relatives aux mesurages
General Information
Relations
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 14685
First edition
2001-12-15
Hydrometric determinations — Geophysical
logging of boreholes for hydrogeological
purposes — Considerations and guidelines
for making measurements
Déterminations hydrométriques — Répertoriage géophysique des trous de
sonde pour des besoins hydrogéologiques — Considérations et lignes
directrices relatives aux mesurages
Reference number
ISO/TR 14685:2001(E)
©
ISO 2001
---------------------- Page: 1 ----------------------
ISO/TR 14685:2001(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2001
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 14685:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Terms and definitions .1
3 Units of measurement.6
4 Purpose of geophysical logging .6
4.1 General.6
4.2 Formation logging .7
4.3 Fluid logging .9
4.4 Construction logging .12
4.5 Selection of logs .12
5 Planning.13
5.1 General considerations.13
5.2 Safety around wells, boreholes and shafts .15
5.3 Site access .15
5.4 Access within a borehole.16
5.5 Equipment .16
5.6 Borehole details.16
5.7 Logging sequence .17
5.8 Quality assurance.18
6 Formation logging .18
6.1 General.18
6.2 Electric logs .18
6.3 Natural gamma-ray logs.21
6.4 Neutron-neutron (porosity) logs .22
6.5 Gamma-gamma (density) logs .23
6.6 Sonic logs.24
6.7 Other logs.25
7 Fluid logging .26
7.1 General.26
7.2 Temperature .26
7.3 Fluid conductivity.26
7.4 Flow.28
8 Construction logging .29
8.1 General.29
8.2 Calliper.29
8.3 Casing collar locator .30
8.4 Cement bond.31
8.5 Closed circuit television log.32
9 Log presentation.32
9.1 General.32
9.2 Track layout.35
9.3 Log parameter scales.35
9.4 Depth scales.35
9.5 Composite logs.35
9.6 Differential logs.36
Bibliography.37
© ISO 2001 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/TR 14685:2001(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted
by the technical committees are circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority
vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature
and does not have to be reviewed until the data it provides are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this Technical Report may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 14685 was prepared by Technical Committee ISO/TC 113, Hydrometric determinations, Subcommittee
SC 8, Ground water.
iv © ISO 2001 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TR 14685:2001(E)
Introduction
Geophysical logging of boreholes, wells and/or shafts (hereafter referred to as boreholes) for hydrogeologic
purposes provides a measurement of various physical and chemical properties of formations penetrated by a
borehole and of their contained fluids. Sondes measuring different parameters are lowered into the borehole and
the continuous depthwise change in a measured parameter is presented graphically as a geophysical log.
Geophysical logging of boreholes is carried out to obtain information on:
a) the lithology of the formations through which the borehole is drilled;
b) the occurrence, quantity, location and quality of formation fluid (usually water);
c) the dimensions, construction and physical condition of the borehole.
The logging equipment consists essentially of three parts: the downhole sensor and oblique tool (hereafter referred
to as a sonde); cable and winch; power and a surface system of power, signal processing and recording units (see
Figure 1).
The various sondes contain sensors to enable specific properties to be measured. Output from the sondes is in the
form of electronic signals, either analogue or digital. These signals are transmitted to the surface instruments via
the cable and winch.
The cable serves the dual purpose of supporting the sonde and conveying electrical power and signals to and from
the sonde. To this end it has a double outer layer of high tensile steel or polyurethane/kevlar.
The winch serves to raise or lower the sonde and to measure its precise depth. This is achieved by passing the
cable round a measuring sheave of known diameter linked to an accurate depth measuring system.
The surface instrumentation typically consists of two sections to provide power and process the electronic signals
from each of the sondes for recording purposes.
Data recorder units are either analogue or digital, comprising pen and ink recorders, film, a dedicated computer,
encoding the signal data from the sonde or surface modules, formatting them and storing them on magnetic tape or
disk, and driving the plotter to produce filed logs.
© ISO 2001 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/TR 14685:2001(E)
Key
1 Sensor 9 Recorder drive 17 ac power source (regulated)
2 Electronic section 10 Winch 18 Recorder
3 Cable head 11 Slip ring 19 Depth indicator
4 Sonde 12 Ground (electric logging) 20 Varying dc voltage (mV) for driving recorder pens
5 Power (down) 13 Motor 21 Logging speed and direction
6 Signal (up) 14 Signal 22 Downhole power (not universal)
7 Logging cable 15 Power 23 Signal conditioning; zero positioning; sensitivity; time
constant etc.
8 Cable-measuring sheave 16 Vertical scale control
24 Logging controls
NOTE Taken from reference [14].
Figure 1 — Schematic of a basic geophysical logging system
vi © ISO 2001 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL REPORT ISO/TR 14685:2001(E)
Hydrometric determinations — Geophysical logging of boreholes
for hydrogeological purposes — Considerations and guidelines for
making measurements
1 Scope
This Technical Report is a summary of best practice for those involved in geophysical borehole logging for
hydrogeological purposes. It describes the factors that need to be considered and the measurements that are
required to be made when logging boreholes. There can, however, be no definite “standard” logging procedure
because of great diversity of objectives, groundwater conditions and available technology. Geophysical logging of
boreholes is an evolving science, continually adopting new and different techniques. Every application poses a
range of problems and is likely to require a particular set of logs to gain maximum information. This Technical
Report therefore provides information on field practice with the objective of how variations in measured parameters
may be useful to take account of particular local conditions. It deals with the usual types of logging carried out for
delineation of aquifer boundaries; mapping aquifer geometry; assessing the chemical quality and quantity of ground
water; water-supply purposes; landfill investigations and contamination studies; borehole construction and
conditions; and subsurface lithological information.
Applications not specifically considered in this Technical Report include mineral and hydrocarbon evaluation and
geotechnical and structural engineering investigations. However, this Technical Report may be a source of general
information for any borehole geophysical logging effort.
NOTE Interpretation of the data collected during logging is referred to in this Technical Report only in a general way. For
full details of the analysis and interpretation of geophysical logs, reference should be made to specialized texts. Examples of
such texts are included in the Bibliography.
2 Terms and definitions
For the purposes of this Technical Report, the following terms and definitions apply.
2.1
abstraction
removal of water from a borehole or well
2.2
access tube
dip tube
pipe inserted into a well to permit safe installation of instruments, thus safeguarding them from touching or
becoming entangled with the pump or other equipment in the well
2.3
air lifting
method of producing a discharge of water from a borehole by the injection of compressed air
2.4
aquifer
lithological unit, group of lithological units, or part of a lithological unit containing sufficient saturated permeable
material to yield significant quantities of water to wells, boreholes, or springs
© ISO 2001 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/TR 14685:2001(E)
2.5
aquifer properties
properties of an aquifer that determine its hydraulic behaviour and its response to abstraction
2.6
argillaceous
containing clay minerals
2.7
bed resolution
minimum bed thickness that can be resolved
2.8
bonding
seal between a borehole lining and the geological formation
2.9
cable boom
rigid support from which the geophysical sonde and cable are suspended
2.10
calibration tail
section of field log carrying information on sonde calibration
2.11
casing
tubular retaining structure, which is installed in a drilled borehole or excavated well, to maintain the borehole
opening
NOTE Plain casing prevents the entry of water.
2.12
casing string
set of lengths of casing assembled for lowering into a borehole
2.13
composite log
several well logs of the same or similar types suitable for correlation, spliced together to form a single continuous
record
2.14
core
section of geological formation obtained from a borehole by drilling
2.15
curve matching
comparison of individual borehole data in graphical form with standard or control data
2.16
drawdown
reduction in static head within the aquifer resulting from abstraction
2.17
drilling circulation
movement of drilling fluid (air foam or liquid) used to clear the borehole during drilling
2 © ISO 2001 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/TR 14685:2001(E)
2.18
filter pack
granular material introduced into a borehole between the aquifer and a screen or perforated lining to prevent or
control the movement of particles from the aquifer into the borehole
2.19
fishing tool
grappling equipment used to locate and recover items from within a borehole
2.20
flushed zone
zone at a relatively short radial distance from the borehole immediately behind the mudcake where all of the pore
spaces are filled with borehole fluid
2.21
fluid column
that part of a borehole filled with fluid
2.22
formation
geological unit or series of units
2.23
geophysical log
continuous record of a physical or chemical property plotted against depth or time
2.24
grain size
principal dimension of the basic particle making up an aquifer or lithological unit
2.25
grout
cement and water mixture
2.26
header information
description of type of data required for inclusion in a table or as input to a computer program
2.27
invaded zone
portion of formation surrounding a borehole into which drilling fluid has partially penetrated
2.28
jig
calibrating device for logging sondes
2.29
leachate
liquid that has percolated through solid wastes
2.30
lining
tube or wall used to support the sides of a well and sometimes to prevent the entry of water
2.31
lithology
physical character and mineralogical composition that gives rise to the appearance and properties of a rock or
sediment
© ISO 2001 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/TR 14685:2001(E)
2.32
logging
recording of data
2.33
mud cake
residue deposited on the borehole wall during drilling
2.34
open borehole
unlined borehole
2.35
packer
device placed in a borehole to seal or plug it at a specific point
2.36
permeability
characteristic of a material that determines the rate at which fluids pass through it under the influence of differential
pressure
2.37
photomultiplier
electronic device for amplifying and converting light pulses into measurable electrical signals
2.38
plummet
plumb bob used for determining the apparent depth of a borehole
2.39
porosity
ratio of the volume of pore space in a sample to the bulk volume of that sample
2.40
rising main
pipe carrying water from within a well to a point of discharge
2.41
rugosity
degree of roughness (of the borehole wall)
2.42
saline interface
boundary between waters of differing salt content
2.43
saturated zone
that part of earthen material normally beneath the water table in which all voids are filled with water that is under a
greater-than-atmospheric pressure
2.44
screen
type of lining tube, with apertures designed to permit the flow of water into a well while preventing the entry of
aquifer or filter pack material
2.45
sidewalling
running a log up or down a borehole with the sonde in contact with the borehole wall
4 © ISO 2001 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/TR 14685:2001(E)
2.46
sonde
cable-suspended probe or tool containing a sensor
2.47
unconfined aquifer
water bearing formation with a free water surface
2.48
unconsolidated rock
rock that lacks natural cementation
2.49
unsaturated zone
that part of earthen material between the land surface and the water table
2.50
washout
cavity formed by the action of drilling
2.51
water table
surface of the saturated zone at which the water pressure is atmospheric
2.52
API unit
American Petroleum Institute unit
unit or counting rate used for scaling gamma-ray logs and neutron logs
© ISO 2001 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO/TR 14685:2001(E)
3 Units of measurement
Table 1 gives a list of parameters and units of measurement in common use. Historically there has been a mix of
units, many from the oil industry and the United States.
Table 1 — Parameters and units of measurement
Parameter Units of measurement Logging method
Electrical resistivity Ωm Resistivity
Electrical conductivity mS/m Induction
Electrical potential mV Spontaneous potential (SP)
Natural gamma radiation API units (see 2.52) Gamma-ray
Percent “matrix” porosity where matrix has to be
Porosity Neutron; gamma-gamma; sonic
stated as sandstone, limestone or dolomite porosity
3
Bulk density g/cm Gamma-gamma (Compton effect)
Acoustic velocity m/s Sonic
Fluid temperature °C Fluid temperature
Temperature gradient °C/m Differential temperature
Fluid conductivity µS/cm Fluid conductivity
2
Conductivity gradient S/m Differential conductivity
Flowmeter; heat pulse flowmeter; tracer pulse
Fluid velocity mm/s flowmeter; packer-flowmeter (PFM); repeated
fluid conductivity/temperature logging
Borehole diameter mm Calliper
Cement bonding % Sonic bond
Casing condition mV Casing collar location (CCL)
4 Purpose of geophysical logging
4.1 General
Ideally, every borehole drilled for hydrogeological purposes should be geophysically logged. For a small
percentage (typically 2 % to 10 %) of the cost of drilling a borehole, the return of information derived from
geophysical logs can far exceed that derived from drilling samples. Logging costs are an even smaller percentage
of total costs for developing a groundwater source or remediation of contamination. Even when a borehole is totally
cored and 100 % recovery is achieved, many geophysical logs will continuously sample many times (10 or more)
the volume of the cores.
Not only are coring and subsequent laboratory analysis very expensive, they are also time-consuming. Long-term
storage of cores presents problems but digital data of geophysical logs can be stored and recalled easily. Whilst
there can be no substitute for high quality lithological samples for determining strata classification, lithology, mineral
content and grain size, the geophysical log provides in situ data on the hydrogeological regime around the
borehole. Also, it provides correction for depth uncertainty of lag in sample collection.
Boreholes drilled for hydrogeological investigation are not often cored and good sample collection techniques are
often difficult to achieve. Sample quality is unpredictable in these circumstances and sampling will not be possible
where drilling circulation is lost. It is in such situations that geophysical logging provides a continuous quantitative
set of data when compared with the drilling samples, which are always subjective. Furthermore geophysical logging
can be used in old boreholes where geological records are undocumented.
6 © ISO 2001 – All rights reserved
---------------------- Page: 12 ----------------------
ISO/TR 14685:2001(E)
In addition to lithological interpretation, a number of physical and chemical properties of the surrounding rock and
fluids contained therein can be investigated.
Geophysical logs can be run in all boreholes including those cased with metal or plastic casing and filled with
water, brine, mud, drilling foam or air. The greatest return of information is derived from open (uncased) boreholes
filled with formation water or mud. In plain-cased boreholes, investigation of the geological formation is limited to
the nuclear logs and, with plastics casing, induction logs may also be used. Conventional resistivity logs (especially
focused ones) are possible to use in plastic screens.
The wealth of information from geophysical logs means that they can be used in many spheres of hydrogeological
investigation; for example, in water resources projects to investigate aquifer hydraulics and distribution of yield
within an aquifer of group of aquifers. In the rapidly expanding field of groundwater quality control, geophysical
logging is now extensively used to monitor groundwater pollution, to trace leachate movement and to monitor the
boundaries between saline interfaces.
Borehole logging is also important in investigating the deep hydraulic and hydrogeological properties of rocks in
geothermal and radioactive waste disposal projects. There are a number of engineering applications of geophysical
logging for investigating borehole conditions and, where television logging is available, for the inspection of casing
and pumps.
Figure 2 shows an example of a composite log where the disposition of aquifers can be seen.
Geophysical logging can be repeated many times in a borehole or series of boreholes at intervals ranging from
minutes to years, adding a new dimension to the information obtainable. This is particularly applicable to aquifer
hydraulics and recharge and pollution studies.
Geophysical logs also provide information that can be directly used in surface geophysical studies for
standardization and calibration of parameters. For example, sonic logs can be calibrated with seismic sections and
resistivity logs can be compared with surface electrical resistivity surveys for resistivity standardization.
4.2 Formation logging
4.2.1 General
No geophysical log has a unique response to a particular rock type or named stratigraphic unit and at some point in
any hydrogeological investigation the formation logs have to be referred to a borehole with a well-described set of
samples.
It is important therefore that formation logs should be run not just in boreholes where incomplete or no samples are
available but in all boreholes, particularly any which have been cored. The three main purposes of formation
logging are described in 4.2.2 to 4.2.4.
4.2.2 Identification of lithology
Geophysical logging can provide a very detailed description of subsurface formation lithologies. Some logs such as
the natural gamma log commonly provide an unambiguous delineation of shale and shale-free zones, with the SP
and electrical resistivity logs supplying supporting evidence. Other logs are generally not diagnostic on their own
but in combination can provide accurate information. The combination of calibrated neutron porosity and density
logs, for example, will differentiate sandstone, limestone and dolomite of different porosities. The additional
information provided by the sonic log enables the identification of halite, gypsum and other minerals.
Where calibrated logs are unavailable, differentiation of lithology will require some geological knowledge, this often
being obtained from examination of core samples or cuttings. Where core recovery is incomplete, geophysical logs
will normally provide a complete lithological description together with accurate depths to lithological boundaries.
The use of geophysical log interpretation is a major factor in the design of casing strings particularly in large
thicknesses of variable unconsolidated alluvial sediments. The positioning of plain and screen casing is commonly
based entirely on a natural gamma log run in a temporarily cased borehole.
© ISO 2001 – All rights reserved 7
---------------------- Page: 13 ----------------------
ISO/TR 14685:2001(E)
Key
1 Poor
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.