Geometrics, Inc.
45 years experience in making geophysical instruments
San Jose, California USA
Douglas Groom, Director of Geoelectrical Products
Geode EM3D
New geophysical instrument for
High-resolution CSAMT surveys
(controlled source audio magnetotellurics)
Minex Central Asia, April 2014
Astana, Kazakhstan
Geode EM3D Features
What is it?
• Distributed network of up to forty EM receivers each
have six channels for total 240 EM channels
• Each receiver configurable for up to six telluric (E-field)
channels and up to three magnetic (H-field) channels
• Durable metal enclosure.
• Low noise front end as low as 10 nV/rtHz
• Low distortion front end
• Automatic calibration in the field
• Automatic contact resistance measurement in the field
• Much more
Highlights
• Synchronized electric and magnetic field
measurements for CSAMT, AMT, and more
• Synchronized by GPS to CSAMT transmitter
• Rugged instrumentation
• Reliable network architecture
• Backed by 45 years of experience in
geophysical instrument manufacture
Geode EM3D 24-Channel Network
20 E – 4 H Channels
Benefits
Why use it?
• High-density 3-D data sets for complete
characterization of your mining prospect
• Rapid data collection with all channels GPSsynchronized to a single transmitter
• Flexible spacing of H-field sensors to maximize
resolution yet minimize cost
• Scalable network from 6 channels up to 240 channels
• Full tensor CSAMT using two transmitter polarizations
• Automatic contact resistance measurement for better
data quality
• In-field calibration for more accurate measurement
• Future AMT, IP, Resistivity modules available
Geode EM3D Single Receiver
High-resolution, high-density EM data with
many sounding stations at the same time
(simultaneous data acquisition).
• Traditional CSAMT uses a separate setup for each
sounding.
• For example, for 50 traditional CSAMT stations
(soundings) the transmitter must be run fifty times and
the station moved 50 times. Typically 30 minutes to
one hour transmitter run time for each station
meaning 50 hours of transmitter time for the survey,
not including setup time.
• Geode EM3D allows a single setup of all stations and
one transmitter run for acquisition of all 50 sounding at
the same time (simultaneous acquisition). That is only
30 to 60 minutes in total for all 50 stations.
Orienting and leveling magnetic coils can be the
most time consuming process in setting up a
station
Geode EM3D offers flexibility in the
use of H-field magnetic sensor coils
• Saves time: Traditional CSAMT requires burying coils for
every sounding. Each time the station is moved the coils
are reburied. Geode EM3D network allows using magnetic
coils on one receiver to be used for multiple soundings on
other receivers so fewer coils need to be buried.
• Improves efficiency: Operator can choose the optimal
number of magnetic coils for the survey needs. For
example H-field measurements can be used for every two
E-field measurements, or maybe only every six, ten, or
more E-field measurements, depending on the complexity
of the geology and the requirements of the survey.
• Improves data quality: Using multiple Hy and Hx on
different receivers, at different locations simultaneously,
allows local referencing to improve data quality.
Flexible networking
Easily scalable system from singlereceiver 6-channel system to 40receiver, 240-channel system
• Maximum flexibility in survey setup. Each
receiver can be any combination of E and H up
to six channels, such as:
• 3E/3H
• 4E/2H
• 5E/1H
• 6E
Field setup and channel parameters
Note automatic contact resistance for every E-field
dipole
GeodEM2010 Acquisition Menu
Note “Measure Contact Resistance” and
“Measure AC & DC Level”
• Contact resistance measured on automatically on all electrode
channels. AC and DC noise level measured automatically.
China GeoTech Beijing
• Introduction of multi-node Geode EM3D to
Chinese
120-Channel, 20-Receiver setup on
bench
Exhibit interest
In-field screen display of test signal
into 120 channel Geode EM3D
Better results with full tensor CSAMT
• Traditional CSAMT only does scalar (Ex/HY)
impedance calculations. The Geode EM3D
can easily do full-tensor measurements (Ex/Hy
and Ey/Hx) using multiple polarizations from
the controlled-source transmitter.
Geode EM3D field test approximately
100 km north of Beijing
• Four receiver network consisting of 20
channels used.
• Four magnetic (H-field) channels
• Sixteen electric (E-field) channels
• Four channels not deployed
Phoenix T-3
3 kW transmitter
Transmitter + Controller + Generator +
PDA Monitor
Planting the transmitter dipole
Grounding transmitter dipole with
metal plates and stakes
Chinese made 30 kW transmitter +
controller + power supplies + junction
boxes + monitoring gear
Two 15 kW generators for 30 kW
Chinese transmitter
Set up frequency scheduler
CSAMT field data
16 channels at 8 Hz with 1.5 kW transmitter at
12.5 km distance
CSAMT field data
16 channels at 8 Hz with transmitter at 12.5 km
distance
Real-time CSAMT impedance curves
for six soundings in field
CSAMT and AMT now with future, IP,
resistivity and other methods in future
• The first Geode EM3D product is controlled
source audio magnetotellurics (CSAMT).
Future products plans include AMT (naturalfield audio magnetotellurics), induced
polarization (IP) resistivity and other
geoelectrical techniques.
Setting parameters for AMT acquisition
Note that seven channels defines tensor site
• Ex, Ey, Hx, Hy, Hz, Hx2 and Hy2 for local reference
AMT real-time times series field display
(natural field with no transmitter)
AMT
AMT
Real-time field data processing
GEM3D receiver with coil cables, porous
pot, dipole cables, battery, Ethernet cable
Retrieving 250-m Ethernet cables at
end of day
System Configurations
• 1. Single Node
– One GeodeEM box used for AMT/CSAMT/IP with
various configurations 6E, 5E1H, 4E2H, 3E3H
• 2. “Typical” Small Networked System
– Four Geode EM3D receivers is the base network, with
various configurations possible
• 3. “Maximum” Networked System
– 40 GeodeEM boxes, i.e. 240 channels.
– 20 Geode EM networ of 110 on display in Laurel
Geophysical booth in exhibition hall.