Exploration Trends & Developments in 2003
Despite advances in airborne magnetic and EM surveying, developments in airborne gravity technology were more significant in 2003. Some sounded like science fiction. SQUIDs are evolving into practical tools. They are used in full-tensor magnetic gradiometers and full-tensor gravity gradiometers as well as in TEM systems. At least three different airborne gravity gradiometers and five airborne gravimeters are in development or use. One system involves magnetic levitation. A turnkey airborne gravimeter is available, as well as an “operator-less” system. Airborne gravity applications are moving into mineral exploration from oil and gas.
Late in December 2003, Exploranium GS Ltd., (Mississauga, Ont.) was acquired by SAIC Canada. Exploranium continues to operate from Mississauga, managed as a division of SAIC’s Transportation and Security Technology (TST) Group.
Quantec Logging Services Inc. (QLS) has officially changed its name to DGI Geoscience Inc. and moved to Toronto with an operations office in Sudbury.
Sander Geophysics Ltd. (SGL) (Ottawa, Ont.) added two fixed-wing aircraft and a helicopter to its fleet. SGL now has a total of 10 aircraft, all modified to reduce their magnetic effect, including six turbine-engine Cessna 208B Grand Caravans and a Eurocopter AS350-B3s.
Val-d’Or Sagax Inc. has changed its name to Abitibi Geophysics. The company will continue to be based in Val-d’Or, Que.
Airborne Geophysical Surveying
Aeroquest Ltd. (Milton, Ont.) reported that in the first six months of 2003 it flew over 30,000 line-km of helicopter time domain EM surveys with major surveys in the Raglan Belt of Quebec. Aeroquest claims that exploration companies are now drilling directly from interpreted AeroTEM targets without the need for ground surveys.
In February 2003 Firefly Aviation Ltd. (Calgary, Alta.) initiated its first international project in which a minimum of 175,000 line-km of survey will be completed in Sierra Leone. Firefly, which specializes in fixed-wing HRAM surveys, completed six surveys totalling 87,000 line-km in Ontario, Nunavut and Sierra Leone.
Fugro Airborne Surveys (Ottawa, Ont.) flew approximately 400,000 line-km in North America last year including more than 50,000 line-km of high-resolution HEM and HMAG data in the Northwest Territories, Nunavut, Ontario, and Quebec, contributing to the discovery of several kimberlite pipes. Over 34,000 line-km of HEM and HMAG were flown for precious metal exploration projects. In late 2003 the Discover Abitibi Initiative (www.discoverabitibi.com) awarded Fugro more than 60,000 line-km of magnetic surveys. MegaTEM surveys were completed in Quebec, Saskatchewan, Ontario, and the United States. GeoTEM surveys were also carried out throughout Canada and in Africa, Europe, the United States, and Brazil. A fixed-wing project, comprising almost 1.65 million line-km, was done in Saudi Arabia. The Fugro airborne gravity system flew over 40,000 line-km of oil and gas surveys in Brazil, Thailand, and Antarctica.
McPhar Geosurveys Ltd. (Newmarket, Ont.) completed aeromagnetic surveys in Bolivia and Mexico. In the Czech Republic a HEM-magnetic-spectrometric survey was carried out. HEM-magnetic surveys were also undertaken in Canada.
Sander flew airborne gravity surveys in Africa, the Middle East, and North America for petroleum exploration and surveys for IOCG deposits (Olympic Dam-type) in North America in 2003. The company also completed a large magnetic gradiometer and radiometric survey in Mauritania as well as several surveys in the United States and the Middle East.
Terraquest Ltd. (Toronto, Ont.) reported a busy year of magnetic surveying throughout North and Central America. The company flew 50,000 line-km using Edcon’s (Denver, Colo.) pre-programmed drape flying technique to map deep structures.
In Airborne Data Acquisition and Processing news, Condor Consulting (Lakewood, Colo.) can now provide processing services for airborne EM data using BHP Billiton’s AirStem software.
New releases in 2003 by Encom Technology Pty Ltd. (Sydney, Australia) include ModelVision Pro Release 5 which has full-tensor 3-D gravity gradiometer modelling and inversion applicable to data from the BHP Billiton Falcon and Bell Geospace airborne gravity gradiometer systems. Encom has added an interface to the University of British Columbia’s Grav3-D and Mag3-D voxel inversion packages and is finalizing research on full-tensor 3-D magnetic modelling applicable to SQUID magnetometers.
Noranda Inc., the University of Quebec Abitibi-Temiscamingue and Fugro continued to enhance MegaTEM data. A set of case histories over the mineral deposits of the Abitibi region including geology, geochemistry and drilling results is well under way.
With the high-resolution data Gedex Inc., (Mississauga, Ont.) expects to acquire with the gravity systems it is developing, the company will provide 2-D maps and inversions to produce 3-D density images using its own inversion algorithm.
IGM Ltd. (Swindon, Wilts, U.K.) released a free viewer for its GeoExpress 3-D software. GeoReviewer is available from its web site at www.geoexpress.co.uk.
Sander released a complete AirGrav dataset from the Timmins region on the Discover Abitibi website. The dataset includes raw and processed AirGrav data, grids, ground data for comparison, and a survey report.
Terraquest is co-operating with Eikon Envirotec Technologies Inc. (Concord, Ont.) on an Ontario Minerals Exploration Technologies (OMET) project to improve aeromagnetic compensation in magnetic terrains. Its magnetic gradient survey aircraft was outfitted with three extra dual-frequency GPS units to measure aircraft orientation.
In Aeromagnetic Surveying, Fugro’s Triax system now has 3-D attitude measurements that allow corrections to be made for aircraft motion on the gradient axes. Advances in HEM technology include Midas, a magnetic gradiometry platform with two magnetometers mounted 12 metres apart, and the horizontal magnetic gradiometer system with two cesium magnetometers in a 5-metre-long rigid Kevlar boom which can be quickly attached to either the Dighem or Resolve EM sensors.
GEM Systems Inc. (Richmond Hill, Ont.) has developed a compact, low-weight potassium vapour gradiometer for remotely controlled aircraft. The GSMP-30S has a total weight of only 1 kg and the sensors can span up to 22 metres wingtip-to-wingtip. The ultimate sensitivity (to sub-pT range) and speed of operation is customer-defined. The first installation is underway overseas.
Goldak Airborne Surveys (Saskatoon, Sask.) now uses high-speed digital video flight path recovery to replace VHS tape. Goldak is also developing the use of GPS antenna arrays on the aircraft to determine X-Y-Z attitude of the aircraft and effectively rotate the Tri-Maxial gradiometer array into a normal orientation to better than 1 in all axes.
RMS Instruments Ltd. (Mississauga, Ont.) will introduce new aeromagnetic compensators and data acquisition systems in late-2004. The compensator will offer enhancements including real-time compensation for up to eight magnetometers, integrated data acquisition, monitoring and recording capabilities, accurate synchronization to GPS, and simplified calibration procedures over the widely used AADCII.
The IPHT (Institute for Physical High Technology in Jena, Germany), has a new generation of SQUID-based high-sensitivity magnetic sensors, the Jessy Star, the world’s first airborne full-tensor magnetic gradiometer. Trials in Germany and South Africa were conducted in helicopter-towed-bird and stinger-mounted fixed-wing installations. Supracon plc (Jena, Germany) will market the Jessy Star system.
Advances in Airborne Electromagnetic Technology were reported by Aeroquest which is building two more AeroTEM-II systems for early-2004, and has also started development of AeroTEM-III due in mid-2004. The next generation AeroTEM system is expected to have a depth penetration in excess of 300 metres, comparable to that of f
In mid-2003 Geotech Ltd. (Aurora, Ont.) introduced a higher powered Mark II version of itsVTEM time domain helicopter system, initially for use in Brazil. Planned upgrades in 2004 include adding a magnetic gradiometer to the system, an X-component receiving coil and a GPS sensor on the transmitter loop. With OMET support, Geotech improved the performance of the Elfmag (digital airborne natural field system) with trial surveys in the Sudbury Basin.
Terraquest reported that development of its XTerraEM two-frequency, fixed-wing EM system is continuing.
In Airborne Gravity Developments, Bell Geospace Inc. (Houston, Tex.) started commercial airborne gravity gradient acquisition (based on declassified military technology) in January 2003 with surveys underway in Africa. Air-FTG is a 3-D full-tensor system that measures all of the independent tensors and the full gravity field. Bell Geospace claims the Air-FTG is the only commercial airborne gradiometer in the world that measures all of the gravity gradients.
In late 2003 Carson Helicopters Inc., Aerogravity Division (Perkasie, Penn.) introduced a new airborne digital unit to increase the sensitivity of its airborne gravity meter measurements.
Fugro introduced new stabilization platforms which have enhanced its L&R total field gravity sensors. The company is also the exclusive partner for Bell Geospace’s Air-FTG system using FTGG technology. Two systems are currently mounted in Cessna Caravan aircraft in Africa and the Americas. Fugro also supports the BHP Billiton Falcon airborne gravity gradiometer system, in a dedicated Cessna Grand Caravan in Australia.
Gedex is developing an airborne gravimeter and airborne gravity gradiometer system, based on laboratory work done by Rio Tinto and the University of Western Australia. The system uses a pair of crossed balance beams and SQUID detectors to sense the spatial gradient in the gravitational acceleration. To obtain the 1 Eotvos laboratory resolution in an airborne environment, Gedex licensed motion isolation mount technology from the Canadian Space Agency. Gedex is currently seeking partners to test fly the system.
A gravimeter system built by Tokimec Inc. (Japan) in 1999 has led to the development of a helicopter gravimeter system, the primary objective of a project funded by the New Energy and Industrial Technology Development Organization (NEDO) in Japan. Measurements were carried out over Japan with good correlation between the airborne gravity anomaly and upward continuation of the ground data.
An airborne gravimeter manufactured by Gravimetric Technology (Moscow, Russia) is available worldwide from Canadian Micro Gravity Pty Ltd. (Perth, Australia). The GT-1A airborne gravimeter has state-of-the-art design and fully automatic operation for measurements.
Scintrex Ltd. (Concord, Ont.) and Lacoste & Romberg Inc. (Austin, Tex.) will offer a turnkey aeromagnetic gravimeter beginning in 2004. The system is built around the L&R Air System II dynamic gravity meter, the latest version of the L&R AirSea meter. Positioning and velocity are determined using dual-frequency GPS receivers on the ground and aircraft. The system includes all the software and components necessary for producing free-air and Bouguer gravity maps.
Ground Survey Techniques
In Data Processing and Positioning news, GEM and Encom have teamed up to develop GEM-VIS, quality control and visualization software which enables users to review magnetometer data, grid results and produce presentations rapidly. GEM-VIS can create a Geosoft Oasis database for quality control and analysis.
Lamontagne Geophysics Ltd. (Kingston, Ont.) reported its MultiLoop 3, thin-foil modelling application can now handle multiple conductors in electrical contact with each other. Higher resolution moment functions were incorporated in the field calculation to make modelling possible at close range to conductors.
In Borehole Geophysics, the new UTEM 4 transmitter (U4TX) system by Lamontagne is optimized for light-gauge loop wire. In routine operation produces a dipole moment swing of 40 million Am2 into a 1.5-km-square loop. The U4TX shows data precision improvements by a factor of six on late channels and an even greater advantage on early channels.
Mount Sopris Instrument Company Inc, (Golden, Colo.) is developing a multi-frequency, four-spacing, complex resistivity IP downhole digital geophysical logging tool which will operate in the time and frequency domains.
In Ground Electromagnetic developments, Crone Geophysics & Exploration Ltd. (Mississauga, Ont.) reported on pros and cons of using high-temperature SQUID sensors in TEM surveys. Crone has been using the CSIROs’ LandTEM sensor in tests and production since 2000. On the ‘pro’ side, SQUID sensors have greater sensitivity, greater depth penetration and better discrimination of highly conductive targets than coils. ‘Cons’ include the restricted number of SQUIDs available, cost of deployment and complexity.
Lamontagne reported on a new surface UTEM system suitable for very low-frequency measurements in which a prototype sensor was successfully tested in 2002 with the UTEM 4 transmitter. A second sensor prototype with even higher sensitivity is being built. The new prototype has effective areas of more than 750 m2 on each axis. Plans call for field testing in early-2004.
IPHT completed trials with its ground-based Jessy Deep sensor (LTc SQUID) in three-vector time domain EM surveys, and the sensor is commercially available from Supracon. Transients of 200 ms and longer have been measured in the DC-to-10k-Hz bandwidth. The magnetometers have a sensitivity of 5 to 50 fT/%Hz. The combination of vector measurements and the high inherent sensitivity of LTc SQUIDS, ensure very high-resolution at low frequencies and a reduced measuring time compared to coils.
In Ground Gravity Surveying a large, three-month GPS-controlled land gravity survey was undertaken by McPhar in Bolivia for an oil and gas company.
In Ground Magnetic Surveying, an new v7.0 series of portable magnetometers with features designed to enhance productivity and ease-of-use was released by GEM Systems. They feature GPS-driven data acquisition; support for line-based formats from Geosoft, Encom and other software suppliers; programmable output; and easy-to-follow lane guidance. Users of v6.0 and v5.0 systems can convert their existing units to v7.0.
In 2003 GF Instruments (Brno, Czech Republic) added several new features to its SM-20 magnetic susceptibility meter. In addition to small size and light weight, the SM-20 offers a shorter measuring time of 1 sec/sample. It also has a scanning mode to obtain a rough average of magnetic susceptibility values (e.g. over outcrops) and faster access to the memory registers.
In Ground-Penetrating Radar news, Sensors & Software Inc. (Mississauga, Ont.) reported there were major changes in the GPR industry in 2003. The US Federal Communications Commission (FCC) has decided that radio frequency geophysical devices, such as GPR, must satisfy regulatory requirements. At Sensors & Software the Noggin GPR product line has been certified by the FCC and is now legal in the United States. New GPR software was also released for data processing and display with the entire range of the company’s GPR instruments.
Resistivity Surveying news included GF Instruments’ introduction of ARES, a third-generation automatic resistivity and IP imaging system. A single, weatherproof unit integrates a powerful transmitter and a sensitive receiver complete with software. ARES can measure resistivity and IP using 2-D/3-D multi-electrode resistivity tomography, VES, resistivity profiling, SP measuring methods, and using up to eight arrays simultaneously.