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3D Borehole Radar™
Product Information
System Configuration
Applications
Survey Data Sheets
Operational Infomation
T&A Survey B.V.Dynamostraat 481014 BK AmsterdamThe NetherlandsT: +31 20 [email protected] www.ta-survey.nl
U.S. Agent:[email protected]: +1 720 2614775
Contents
3D Borehole Radar: A Breakthrough in Ground Penetrating Radar Survey ..................... 2
System Configuration Prototype .............................................................................. 4
3D BHR Next Generation Tool: Technical Plan Summary ............................................. 6
Application: Oil and Gas Exploration ......................................................................... 7
Application: Mining Industry ................................................................................... 8
Application: Geothermal Energy Detection ................................................................ 9
Application: Geotechnical Survey ........................................................................... 10
Application: Determination of Jet Grout Column Diameter ........................................ 11
Application: Tunnel Track Exploration ..................................................................... 12
Application: Detection of Unexploded Ordnance (UXO) ............................................. 13
Data Sheet 1: Water Test Case ............................................................................. 14
Data Sheet 2: Soil Test Case ................................................................................. 16
Data Sheet 3: Sheet Piling Wall ............................................................................. 18
Data Sheet 4: Object Classification ........................................................................ 19
Operational Information ....................................................................................... 20
3D Borehole Radar 2
3D Borehole Radar: A Breakthrough in Ground
Penetrating Radar Survey
About T&A Survey
T&A Survey is an experienced and technologically advanced subsurface research company
founded in 1992 in Amsterdam, The Netherlands. T&A specializes in geological and
geophysical studies of the deep underground and the development of geophysical
hardware and software. Our customers include all major Dutch engineering
companies, building contractors, oil and gas companies as well as regional and national
authorities. Interest in T&A Survey from large, multi-national oil and gas companies
continues to increase as T&A has demonstrated its continued development with proven
technology.
Robert van Ingen is the single shareholder and Managing Director. He holds an MSc in
Geology and has 25 years of experience in geophysics with Atlas Wireline Services and
Jason (Fugro). T&A employs highly qualified engineers from the Universities of Zürich,
Utrecht, Delft and Amsterdam, ensuring optimum performance in projects undertaken.
The Technology
T&A Survey was founded on the principal and Robert’s personal belief that the success of
the company would be in direct response to its commitment to investing in research and
development. These R&D efforts have resulted in the patented 3D Borehole Radar (3D BHR)
technique. Applications for this technique include oil and gas exploration, mining and
geothermal applications.
As a non-seismic tool, it can add useful information to existing logging techniques. Due
to the unprecedented penetration of the directional radar signal, combined with its
typical high resolution, it is able to investigate the first few meters of the reservoir
formation and build up a fully detailed 3D image of the surrounding borehole. This is the
first time that it is possible to obtain high-resolution information from the borehole
surroundings and not only from the borehole wall.
3D Borehole Radar applications for oil and gas are as a wireline logging, measurement
while drilling (MWD), and a geosteering tool especially in thin pay zones. This facilitates
the 3D positioning of the drill bit, reservoir characterization, fracture detection and 3D
monitoring of the steam/waterfront. T&A Survey believes the technology is uniquely
effective and profitable with other multiple applications such as SAGD and as a fishing
tool.
3D Borehole Radar 3
In order to use the 3D BHR in the oil & gas exploration and production industry it needs
to be adapted to function in the high temperature and high pressure conditions which
commonly occur in deep-lying reservoirs. Furthermore, it needs to be adapted to the
data communications and drill pipe industry standards. The first step in this R&D process
is the proof of concept for geological applications of the tool, for which a “next
generation” 3D BHR tool is required.
Applications of the 3D BHR:
• Oil and gas reservoir
characterization
• Mining
• Geothermal energy detection
• Geotechnical survey
• Determination of jet grout
column diameter
• Tunnel track exploration • Object detection
3D Borehole Radar 4
System Configuration Prototype
The 3D Borehole Radar system is pulled or pushed through a
non-metallic cased and water-filled borehole. It consists of
four main parts:
1. Positioning unit
The positioning unit contains a control unit, a motor to rotate
the radar unit and several sensors to determine the position of
the system in the borehole. The sensors consist of
magnetometers, accelerometers, FOG gyroscopes sensors and
an angle encoder. This unit is the outer shell of the complete
3D BHR system as it has a specially designed housing for the
enclosed radar unit, protecting it from mechanical and
environmental borehole conditions.
2. Radar unit
The radar unit is enclosed and rotates inside the 3D BHR
system. It contains two directional antennas. The
reflectors behind the antennas provide the directional
sensitivity and the energy bundling of the antenna.
The control unit, transmitter electronics and receiver
electronics are also situated in the radar unit. The
recorded analogue data is digitized down hole by a very
fast A/D converter.
3. Cable
The 3D BHR is connected to the surface by a cable which
supplies power and allows high-speed data transmission.
At the surface, the data is stored and can then be
processed to provide a 3D image of the borehole
surroundings.
4. Software
The 3D BHR is supplied with custom designed operating
and processing software, called Dafos, which can also be
used by other geophysical equipment containing multiple
sensors.
Accessories
Depending on the application, the following accessories
are required to operate the 3D BHR:
Tripod
Winch
Surface equipment (DC power supply, computer
and housing)
15.9 cm
A specially designed connection between the
positioning unit and radar unit allows high-speed data communication and power supply during rotation.
and power supply during
rotation.
3D Borehole Radar 5
Technical Specifications
Length 4.2 meters
Diameter 16 centimeters
Weight 250 kg
Source signal impulse (up to 850 V)
Centre frequency 100 MHz
Sample frequency 600 MHz
Bandwidth 100 MHz
Dynamic range between
transmitter/receiver
120 dB
Avg. penetration 5 – 15 meters
Avg. angle accuracy 1– 30 degrees
Avg. axial accuracy 1 – 30 centimeters
Conductivity range 20 mS/m @ 100MHz and lower
Antenna set-up bistatic (two antennas)
Antenna type shielded dipole (directional)
Temperature rage 0˚C - 60˚C
Max. pressure 15 bar (150 meters in vertical water-
filled borehole)
Avg. power consumption 60 Watts
Material RVS 316 (non-magnetic) and
composite materials
T&A operates on a policy of continuous product improvement. Future series of the 3D
BHR will be smaller and possess extended temperature and pressure ranges.
Versions
The 3D BHR is available in different versions, from a full-service modular geophysical tool
to a stand-alone radar module.
3D BHR Omni To be used in cased boreholes (in every position)
Parts: positioning and radar unit, housing and cable
Length: 4.2 meters, Weight: 250 kg
Extras: centralizers for open boreholes
3D BHR Vertical Only to be used in vertical boreholes.
Parts: Integrated positioning and radar unit (more robust)
Length: 3.2 meters, Weight: 200 kg
Parts: 1 (integrated rotor/stator and cable)
3D BHR Probe A system of a separate radar unit (with embedded software)
To be integrated in other equipment
Length: 1.50 meters, Weight: 65 kg
3D Borehole Radar 6
3D BHR Next Generation Tool: Technical Plan Summary
The current first generation 3D Borehole Radar (3D BHR) tool was built based on the
following design criteria:
Application: detection of metal objects
Shallow boreholes, maximum depth 30 m, later on extended to 90 m
Rugged design
Because of continuous product development, the demand for new (geological)
applications and the major technical improvements in the hardware components and
operating and processing software for the tool, the need for a new tool has arisen. The
next generation 3D BHR should be applicable at greater depths up to 300 m.
Furthermore, the tool should be suitable for a wider range of applications, such as Oil &
Gas exploration and geothermal research. The new tool should be able to withstand the
following, still moderate, environmental circumstances: a temperature of 30 °C and a
borehole pressure of 35 bar.
Design Criteria
Based on the above information, including the accumulated experience to date with the
current tool, we propose the following changes with respect to the current system:
Adaption of the housing to 30 °C and 35 bar
Reduced overall diameter of the tool
Changes in antenna system configuration
Modified pulse generator pulse shape, improved matching to antenna system
Modified low noise front-end
Enlarged ADC (analogue to digital conversion) resolution
Light weight rotor and driving motor for power reduction
An option for down-hole data storage
Possibly a down-hole battery pack instead of on-line power
Fibre optic borehole data cable instead of metal coaxial cable
3D Borehole Radar 7
Application: Oil and Gas Exploration
The 3D Borehole Radar technology is a promising addition
to existing logging techniques used in oil and gas
exploration and production. The main benefit of the
3D BHR is the ability to see beyond the borehole.
Applications:
Monitor steam/water front
Fracture geometry (m to decametre scale)
Karst detection (m to decametre scale)
BHA
Measurement While Drilling
Geosteering
Steam-assisted gravity drainage (SAGD)
Very shallow oil reserves with horizontal wells
Monitor proppant placement
Time lapse measurement to image (saline) tracers
Penetration range
The penetration range of the 3D Borehole Radar system in reservoirs is 5 to 10 meters,
based on average reservoir properties (see table). Penetration range increases with
increasing resistivity. In ideal situations, a penetration range of 15 meters can be
obtained.
Reservoir Permittivity Resistivity [Ohm-m]
Oil-bearing 10 50
Water-bearing 20 2
T = 120º C and p = 300,000 hPa
Main Advantages
• 3D BHR detects the position of the oil-water contact zone in reservoirs
because the electromagnetic impedance contrast is higher than the contrast
in acoustic impedance.
• In SAGD, 3D BHR provides an accurate relative position of the two wells from
only one borehole without needing access to the producer well.
• In thin pay zones, 3D BHR provides the information to steer the drill bit. The
distance to the top and bottom of the reservoir can also be measured.
• In production phases, the 3D BHR monitors the movement of the
steam/water front in 3D.
• In an exploration environment, the 3D BHR can be used as an Electric
Propagation Tool to detect the electrical properties of the formation.
3D Borehole Radar 8
Application: Mining Industry
The mining industry is all about knowing what's going on in the underground. Without
subsurface testing, it is impossible to locate an ore body, to define exploitable reserves
or to design a mine plan.
Geophysical tools used in the oil industry
(such as 3D seismic techniques) have been
adapted and applied in mining industry,
resulting in great benefits for the exploration
of mines. However useful these tools may be,
none of them can compete with the 3D
Borehole Radar’s capacity to reveal a high-
resolution contrast between different
materials in the underground.
Main applications
The 3D Borehole Radar provides a useful
addition to existing geophysical techniques in
recognizing geology for mining. It can be applied
in both exploration and production phases.
In an exploration environment, the 3D Borehole
Radar can be applied in horizontal and vertical
drillings into e.g. coal, ore and salt bodies.
Depending on the resistivity of the formation,
the signals penetrate up to 20 meters around
the borehole. It can be used for detecting:
• Lateral and vertical inhomogeneities
• Cavities
• Faults
• Fracture zones: length, dip and distance
Other possible applications are:
• Locating an ore body
• Defining exploitable reserves
• Designing a mine plan
• Detecting pot holes
Main advantages
In an exploration environment:
• High-resolution data:
transitions can be detected
with great accuracy.
• Directional data: a 3D
image of geological situation
around the borehole is
obtained
• High penetration range up
to 20 meters.
In a production environment:
• monitoring and locating
potential mining problems.
• finding zones of potential
danger due to caving and
shock bumps.
• finding hazardous structures
like water bearing fissures
ahead of planned mine
development.
3D Borehole Radar 9
Application: Geothermal Energy Detection
Due to increasing scarcity in oil and gas
resources, energy costs are rising and so is the
demand for alternative resources. Deep
geothermal energy is an alternative energy source
with great advantages, which could become more
and more important.
Geothermal Energy is generated by pumping up
deep groundwater from a depth of 1.5 to 4.0
kilometers with a temperature of 70 to 100
degrees Celsius, in order to heat houses and/or
horticulture greenhouses. After releasing its heat,
the groundwater is pumped back into the
groundwater reservoir. This energy source is
almost inexhaustible.
Mapping deep groundwater reservoirs
In order for a geothermal project to be successful,
it is important to study the geological structure
and stratigraphy of the subsurface of the planned
location. The research target of a geological study is to map deep groundwater
reservoirs. The results of the study include a detailed description of, for example, the
geometry and other properties of the reservoir. The completed study is comprised with
other drillings, wire line logs and cores.
Main applications
The groundwater reservoir needs to be estimated very accurately prior to making the
decision whether a geothermal system can be successfully and economically exploited.
Additional information, next to the wire line logs, can be obtained by 3D Borehole radar
measurements. 3D Borehole
Radar data can be used to
delineate the location and
dimensions of the reservoir
and to determine the presence
of impermeable cap rock on
top of the groundwater
reservoir. Faults and fractures
can be detected, including dip
measurements.
Main advantages
• 3D BHR can be applied in vertical and
horizontal drillings into the formation to
detect transitions between different
rock types and to detect and delineate
cavities, faults and fractures.
• 3D BHR provides 3D positioning of
interesting features.
• 3D BHR provides high accuracy data.
• 3D BHR provides a high penetration
range compared to other geophysical survey methods.
3D Borehole Radar 10
Application: Geotechnical Survey
Measurement of underground structures (concrete
piles, sheet piles and foundations) are important in
order to verify their exact location and dimensions
and to check possible damage or degradation. After
many years, the exact location of structures is often
unknown and needs to be determined again.
Measurement of underground structures with
conventional surface measurement techniques are
operationally difficult and tend to be unreliable for
several reasons:
• The structures are positioned too deep for
conventional measuring.
• The current surface techniques prevents
conducting overburden.
• The current techniques do not provide enough
resolution.
• The existing above ground structures makes measuring difficult.
Steered Drilling
Steered drilling is a new technique for laying underground cables. As an alternative to
digging trenches, it is a cost-effective method that causes fewer disturbances to the
environment. As the number of cables and other objects in the shallow subsurface
increases, there is more need for exploration of the drilling path. As an alternative to
measurements from the surface, the high-resolution directional borehole radar can be
integrated in the drilling process to explore the drilling path in advance.
Main advantages
• The radar is brought down to the location
of the object in the subsurface.
• No overburden effects.
• Much higher resolution with the acquired
images.
• No site constraints with surface structures
as boreholes can be drilled at any angle or even horizontally.
3D Borehole Radar 11
Application: Determination of Jet Grout Column Diameter
Measuring jet grout columns
Concrete foundations are used for an increasing number of underground infrastructure
projects. Various jet grout injections consolidate the soil and decrease the risks of
subsidence from large surface structures.
Jet grout columns vary in diameter, depending upon the injection pressure and the soil
conditions. The diameter is an important property that should be quantified, especially
when several grout columns are connected to form an underground concrete floor.
Until now, no proven or tested techniques existed to calculate the diameter of
injected columns. Until now, it has been almost impossible to conclude whether the
jetgrout foundations provide enough stability, especially in underpinning applications.
Main applications
By integrating the 3D Borehole Radar technology into the injection
lance, the diameter of the column can be determined on site. The
boundary between grout column and hosting medium is a sharp edge
and, therefore, a good
reflector for incident radar waves.
There are two ways to apply the 3D BHR in the jet grouting process.
In both cases, the diameter can be measured very precisely because
of the resolution of the 3D Borehole Radar method:
Integrating the 3D BHR in the jet grouting system. During construction of
the column, the radar is located just below the injection point and the grout
column diameter is measured from within the column. The injection pressure can
be adjusted while the column is being made.
Drilling a borehole near the grout column allows the 3D BHR to measure the
distance from this borehole to the edge of the column.
Main advantages
The diameter of a jet grout column can be measured very precisely, because of
the resolution of the 3D Borehole Radar method.
3D Borehole Radar 12
Application: Tunnel Track Exploration
It is essential that any tunnel project starts with a comprehensive investigation of ground
conditions. In addition, encountering unforeseen ground conditions, objects or anomalies
can be costly in terms of time and materials. The 3D Borehole Radar technique
continuously gathers detailed information about obstacles and geological transition
zones.
Main applications
The 3D BHR is positioned in a
horizontal borehole with a diameter of
about 20 centimeters, and drilled
along the planned trajectory. It
measures the complete surroundings
of the borehole. Rotating 360°, it
gathers and processes data from all
angles with special proprietary
software. After processing, the raw
ground penetrating radar data is
combined with simultaneously
collected positioning data, providing
meaningful operating data.
T&A is the first geophysical survey company to successfully integrate radar electronics
into a geophysical tool. It is capable of surveying the surrounding soil construction and
simultaneously determining the exact position of objects from within one borehole.
Main advantages
• Better analysis: The complete tunnel track can be explored in advance,
identifying the exact location of fault zones.
• More efficient use of TBM’s: As more relevant information is available
during drilling, it allows for more precise decision-making.
• Substantial technical and financial risks can be avoided. • Enhanced safety during tunnel construction.
3D Borehole Radar 13
Application: Detection of Unexploded Ordnance (UXO)
Unexploded ordnance, such as aircraft bombs and
artillery shells from for example World War II still
can be found in the subsurface throughout Europe.
These explosives are especially dangerous when
touched or moved during digging, dredging or piling
activities.
Detection from the surface is often not feasible, since
the explosives are buried too deep. When a bomb
dropped from an airplane doesn't explode touching
the surface, it penetrates the upper soft peat and
clay layer and stops at the first stable sand layer. In
the Netherlands, this layer can be located at a depth
of more than 10 meters below the surface. Due to
resolution problems, detection from the surface is
not an option in these cases. Measurements from a
borehole are needed to solve the problem.
Traditionally, these measurements are done using a
magnetometer.
The main drawbacks of the magnetometer method are:
Limited penetration range of 1 to 2 meters.
The measurements contain no directional information.
Main applications
For 3D Borehole Radar measurements, a
borehole is drilled in a safe zone, just
outside the investigation area. When it's
determined that the area around this
borehole is safe, the next measurement is
done in an adjacent position closer to the
area of investigation. This way the whole
area is searched for deep explosives.
Unexploded bombs with a large metal
content show a strong electrical contrast
with the surrounding soil. Therefore, these
objects are very good reflectors of radar
waves.
Main advantages
High penetration range of 5-15
metres reduces the number of
boreholes considerably. Even
with a penetration range of
only 5 meters, the number of
required boreholes is reduced
by a factor of 25 compared to
the magnetometer method.
Very high location accuracy due
to the nature of the radar
method and the directional
radiation pattern that is transmitted by the 3D BHR.
3D Borehole Radar 14
Data Sheet 1: Water Test Case
Objective and circumstances
The first measurements in water were carried out to calibrate the
3D Borehole Radar. These measurements took place in a water
basin at the TNO Physics and Electronics Laboratory. An iron gas
cylinder was hung next to the 3D BHR at a distance of 1.5
meters from the 3D BHR, at a depth of 2 meters below water
level and at an angle of 270º.
Radiation pattern
The 3D BHR was positioned vertically in the water basin. This
way, the transmitted signal travels along a horizontal plane, as
shown in the figure below. The radar unit of the 3D BHR rotates,
so it is a directional device. This means that the signal that is
transmitted has an angular movement in the horizontal plane. In
both vertical and angular (horizontal) direction, the signal is not
transmitted in a single direction but in a bundle of directions.
This bundle has a width of 10-15º in vertical direction and a
width of 70-90º in angular direction. The two bundles combined
form what we call a detection cone. The energy density of the
transmitted signal is strongest in the middle of the cone. Because
of this, in measured data, objects are visible within a certain
angle and depth range and not at one single angle/depth
position. Note also that, because a separate transmitting and
receiving antenna are used, the detection cone starts at a small
radial distance from the antennas.
Detection cone
Detected object
70-90°
Horizontal plane
Transmitting antenna
10-15°
Detection cone
Receiving antenna
Rays that hit the receiver
Detected object
Side view Top view
Rays that miss the receiver
3D Borehole Radar 15
Measurement results
The figure to the left shows a
vertical angle scan of the
gas cylinder measurement.
All data in a vertical angle
scan have the same
measurement angle. The x-
axis represents the radial
distance from the 3D BHR
and the y-axis the depth
below water surface. The
radial distance is converted
from measurement time,
using the relative permittivity
of water.
The figure shows the reflection of the cylinder at a depth of 2 meters below water surface
and at a radial distance of 1.5 meters from the 3D BHR. In the vertical direction, one can
see the same hyperbolic reflection pattern that is characteristic for surface ground
penetrating radar. This is because, as the 3D BHR is lifted vertically and ‘passes’ the
object, the distance between the object and the 3D BHR first decreases and subsequently
increases.
The figure to the right shows a
horizontal depth scan of the
same measurement. All data in a
horizontal depth scan have the
same measurement depth, in this
case, 2 meters below the water
surface. The radial axis is the
radial distance from the 3D BHR
and the angular axis is the angle in
relation to the magnetic North.
The figure shows the reflection
from the cylinder at an angle of
270º with respect to magnetic
North and at a radial distance of
1.5 meters from the 3D BHR, a
prove of the excellent directionality
of the system.
In a horizontal depth scan, one doesn’t see a hyperbolic reflection pattern. This is
because, as the 3D BHR rotates and horizontally passes the object, the distance between
the object and the 3D BHR remains constant. What does change, however, is the
intensity of the radiated wave. It increases and subsequently decreases as the antenna
radiation beam horizontally passes the object. This results in the kind of ‘banana’ pattern
that can be seen in the figure. The object is located in the middle of this pattern.
3D Borehole Radar 16
Data Sheet 2: Soil Test Case
Objective and circumstances
The water test case was repeated under the real circumstances of the subsoil. In this
test, the 3D Borehole Radar (3D BHR) was placed in one borehole and an iron cylinder of
10 cm. in diameter and 30 cm. in height was placed in another.
The cylinder was placed at depth of 6
meters, at a radial distance of 9
meters and at an angle of 345 degrees
relating to the magnetic North from
the 3D BHR.
The soil was composed of
homogeneous sand and was water-
saturated to about half a meter below
the surface. Conductivity was low.
Measurement results
The figure below shows the measured raw data. No processing has been done yet. The
figure shows a vertical angle scan of the measurement data. All data in a vertical angle
scan have the same measurement angle. The x-axis is the radial distance from the 3D
BHR and the y-axis is the depth below surface. The radial distance is converted from
measurement time, using the relative permittivity of the soil.
The large amplitude at small distance, which corresponds with small amount of time, is
the direct wave. This is the signal that travels directly (without reflection) from
transmitter to receiver antenna. The object cannot be seen in this unprocessed data.
3D Borehole Radar 17
The figure to the left shows a
vertical angle scan of the
cylinder after processing. The
direct wave has been
suppressed and the reflection
from the cylinder now appears
at a depth of 6 meters below
surface and at a radial distance
of 9 meters from the 3D BHR,
the exact position of the object!
The figure to the right shows a
horizontal depth scan of the same
measurement. All data in a
horizontal depth scan have the
same measurement depth, in this
case 6 meters below the surface.
The radial axis is the radial
distance from the 3D BHR and the
angular axis is the angle in relation
to the magnetic North.
The figure shows the reflection
from the cylinder at an angle of
345 degrees and at a radial
distance of 9 meters from the 3D
BHR, again the exact position of
the object!
Although the bottle object has a diameter of only 10 centimeters, the object appears in
the data not only at an angle of 345 degrees, but over an angle range of about 300 to 30
degrees. This is because the 3D BHR transmits a bundle of signals with a width of 70 to
90 degrees. The energy density of the transmitted signal is the strongest in the middle of
this bundle.
This test case proved the excellent performance of the 3D BHR with regard to
directionality and accuracy, not only under laboratory circumstances, but also in a real-
life case of a subsoil survey. It shows the system is able to detect the exact position of
an object placed at 9 meters from a single borehole, which is an unprecedented result in
ground penetrating radar survey.
3D Borehole Radar 18
Data Sheet 3: Sheet Piling Wall
Survey objective and circumstances
In this survey, the objective was to detect a sheet piling metal wall in the subsoil. The
measurements were carried out from a 15-metre deep, PVC-cased borehole. The local
subsoil consisted of peat material (from the surface until 6 meter depth) and below it
consisted of sand. The metal wall was located at 2.8 meters horizontally from the 3D
Borehole Radar (3D BHR) and had a depth of 10 meters. The subsoil water table was
very near to the surface. The conductivity of the water-saturated subsoil was rated fairly
high.
Measurement results
The figure to the right shows a
vertical angle scan of the
measurement. All data in this
a scan have the same
measurement angle. The x-
axis represents the radial
distance from the Borehole
and the y-axis the depth
below water surface. The
radial distance is converted
from measurement time, using
the relative permittivity of the
soil. The figure shows the
results after data processing.
One can see the reflection of
the metal wall up to a depth of
about 10 meters and at a
distance of 2.5 meters from
the 3D BHR.
The figure to the right shows a horizontal
depth scan of the same measurement. All
data in this scan has the same
measurement depth, in this case 8 meters
below the surface. The radial axis is the
radial distance from the 3D BHR and the
angular axis is the angle in relation to the
magnetic North.
The figure shows the wave reflection from
the wall at an angle of 200 degrees and at
a radial distance of 2.5 meters from the 3D
BHR.
3D Borehole Radar 19
Data Sheet 4: Object Classification
Objective and circumstances
The objective of the survey was to determine
whether objects encountered during drilling
could be World War II conventional explosives.
During drilling activities, an object was hit at 8
m depth, which caused the drill bar to break.
Because of the history of the area, the
presence of either explosives or a bunker in the
underground could not be excluded. To
minimize risks during further drilling activities,
a 3D BHR survey was carried out at the drill
hole location. The specific goal in this survey
was to determine the dimensions of the object and whether it was part of a larger structure
like a bunker.
Measurement results
The results of the measurements indicated that the object was not part of a larger
structure. The survey also indicated that the object was located at a depth of 5 meters.
This conclusion was later confirmed by magnetometer measurements.
The figure to the left shows a
vertical cross-section of the
data at a single angle of 2.8º.
The absolute value of the
data is shown, the wave
pattern of the data has been
removed. The object is
represented by the yellow
color at 5 meters depth and
3.5 meters radial distance.
The red color at small radial
distances represents the
direct wave between
transmitter and receiver
antenna.
3D Borehole Radar 20
Operational Information
Equipment
The field crew needs a flat surface of about 40 m² near the
borehole to unpack and mount the equipment. Computers
and monitors need to be protected from rain and dirt, either
by a shelter or by a van. Setting up the equipment takes
approximately 60 minutes for two operators.
Auxiliary equipment
Auxiliary equipment needed to operate the 3D BHR:
Crane, rig or tripod
Winch
Power supply
Water supply
The mounted 3D BHR is 4.4 meters long, has a diameter
of 16 centimeters and weighs approximately 250
kilograms, so it needs to be lifted by a crane or, when
using a tripod, by an electrical winch. The crane or tripod
must be able to lift the 3D BHR approximately 5.0 meters
above borehole casing level. The cable speed of the crane
or winch must be reducible
to 1 meter per minute.
Boreholes
Boreholes can have a maximum depth of 30 meter and need
to be cased using PVC pipes or any other non-metallic (non-
conductive) material. Preferably, they have a inner diameter
of approximately 20 cm, with a minimum inner diameter of
19 cm and a maximum inner diameter of 24 cm. During
measurements, these holes need to be filled with fresh
water up to the edge of the casing.
If the groundwater table is low, for example, a few
meters below the surface, it is recommended to plug the
bottom end of the casing using a lid or clay in order to
avoid losing borehole water during measurements. A
fresh water supply is needed to maintain a stable water
reference level at all times.
Right: Water fill and depth reference.
Left: Wheel blocks at top and bottom will centralize the 3D BHR. An
inner diameter of 20 cm is ideal.
3D Borehole Radar 21
Connection
The cable can be connected
in multiple ways, using hooks
or pulleys as indicated in the
pictures. The inner diameter
of the eye on top of the
upper wheel block is 34 mm.
Left: ribbon
Right: hook
Procedure
The 3D BHR is lowered into the borehole, followed by a heating up period of 15 minutes.
After heating up, the 3D BHR is lifted slowly (1 meter per minute) while measuring.
When the 3D BHR is surfacing, the measurements are stopped.
Left:
Lowering
Middle:
Heating and
starting
Right:
Stopping
Power supply
230 V/50 Hz/200 W or 24 Vdc/8A
Objects on the site
Large objects at the surface of the site like steel pylons, metal plates, concrete walls will
cause interference with the 3D BHR measurements. Please provide us all the information
to make sure that 3D BHR measurements can be performed under the given conditions.
The presence of power cables near a borehole should be avoided as much as possible.
Weather conditions
Weather conditions, except lightning, do not influence 3D BHR measurements. In the
case of lightning, measuring will stop until the weather improves.
The minimum temperature during operation is –5 °C as lower temperatures can damage
the water filled 3D BHR system.
3D Borehole Radar 22
Summary
Crane, rig or tripod cable length Approximately 30 meters of free cable length
Crane, rig or tripod weight
lifting
Approximately 250 kg
Crane, rig or tripod cable
pulling velocity
Approximately 1.0 meter/minute during measuring
Boreholes Maximum depth 30 meter, PVC cased (or similar)
inner diameter 20 cm, closed at bottom end in
certain situations
Connection Eye in top wheel block 34 mm inner diameter
Power supply 230 V/50 Hz/200 W or 24 Vdc/8A
Water supply Fresh water, quantity depending on geology, water
table height and site.
Object on the site Contact us
Power cables nearby Contact us
Weather condition Minimum temperature –5 °C