Airborne geophysical surveys

The more you understand about your project in the early stages, the better you are able to plan for, and manage risk for the ultimate success of the project. Where unknown factors and conditions exist, there is significant risk that can produce additional costs and expensive delays. All projects, from those of a regional nature to those with a small footprint, benefit from an understanding of the geology in the near surface. Airborne geophysical surveys offer mature, non-invasive technologies that provide systematic, quantitative, rapid, cost-effective, information about the near-surface in the project area.

Modern airborne geophysical methods offer accurate, high precision, calibrated data sets which measure the electrical conductivity, magnetization, natural radioactivity, topography, and density. The correct combination of these methods for a given project will provide valuable layers of information for integration and interpretation of the surface and sub-surface characteristics.

The Aeroquest International Group of Companies provides a full range of airborne methods and services throughout the world. With a presence on every continent (barring Antarctica), and as a public company focused exclusively on airborne surveying, Aeroquest is uniquely positioned to deliver customized turnkey airborne services wherever the project is located. Aeroquest is focused on raising the bar in the Airborne Geophysics Industry, building on its past successes and leadership in our industry. The UTS arm of the company was the first to offer compensated, stinger-mounted magnetics on a helicopter for high resolution, high accuracy magnetic mapping in any terrain. UTS continued to innovate, and developed Ultra High Resolution Airborne Magnetic and Radiometric (UHRAM) surveys. These surveys offer the highest resolution data sets available from a fixed wing platform and are delivered using purpose-built crop-duster aircraft capable of flying safely as low as 15-20 metres above the ground. Aeroquest was also the first to commercially offer helicopter-borne time-domain electromagnetic (HTEM) surveys. Aeroquest's AeroTEM HTEM system has an excellent reputation earned through responding to explorationists' need for a combination of spatial resolution and depth penetration.

AeroTEM is a helicopter-towed electromagnetic system first developed in 1998. These systems have powerful transmitters that allow for mapping to depths of several hundred metres with great spatial resolution and detail. The AeroTEM system is well-suited to the delineation and interpretation of both discrete targets and stratigraphy in many environments. The AeroTEM system is designed for application to a wide variety of markets including mineral exploration, oil and gas exploration, engineering, groundwater, and environmental. Helicopter-based systems provide project managers with many technical and logistical advantages, the AeroTEM system can be quickly employed and has been credited with a number of mineral discoveries. The AeroTEM system continues to be recognized as an industry leading technology worldwide.

In this example, the AeroTEM survey is interpreted to produce a 3-D model of the variation in the electrical conductivity of the ground. These results are used to map the continuity, thickness and depth of the various layers across the survey area. A conductive shale formation in this area is very important in delineating the underlying sandstone (the reservoir rock), and is also an important element in defining the mining/extraction process for Oil Sands. The AeroTEM results also effectively map the distribution of aggregate resources at surface. Paleochannels are mapped as relatively resistive units with a very clear morphology and are important as sources of aggregate and water, and for planning the oil sand extraction process. The spatial resolution of the AeroTEM system allows for detailed mapping of these channels and their relationship with the stratigraphy.

The conductivity depth slices above show the detailed mapping capability that the AeroTEM system can provide. The left image shows the conductivity distribution in the near-surface (30 m), the middle image at greater depth (100 m), and the right image at still greater depth (160 m). The dark orange region in the south central area of the image at the left maps a deposit of sand to a depth of 120 m. Note that the conductive shale unit shown as the cooler colours dips gently to the east. Note also the high degree of detail mapped within the shale unit. A paleochannel system is clearly mapped in the northwestern and northern portion of the survey area and likely cuts through the shale formation. Inversion of AeroTEM data can also map the variation of conductivity within the Oil Sand itself. Less conductive regions are more likely to reflect lean Oil Sand, and the least conductive areas often reflect the richest Oil Sand. When combined with even sparse drilling information, AeroTEM survey data can accurately delineate the thickness of the Oil Sands.

The application of this technology is virtually limitless. In western Africa, AeroTEM was effective in locating and characterising conductive ground sinks for electrical transmission lines. In eastern Africa, AeroTEM was combined with the magnetic and radiometric methods for mapping potential gas seeps across a prospective licence area. Combining the appropriate EM technology with magnetics and radiometrics allows for the layering of information for a more effective and robust interpretation of the survey results. AeroTEM is currently being used in Yemen for the characterization of the low velocity layer to improve the static correction of noisy seismic data. The system has also been successful in determining the thickness of sand dunes to map the variation in the underlying strata. And AeroTEM has been attributed to several mineral exploration discoveries in the search for nickel, diamonds, and base metals.

Aeroquest's history is proof of capable guidance, growing an innovative, full-service airborne geophysical company that provides service globally to multiple markets. The company as a whole has acquired and delivered more than 9 million line kilometres of high-resolution airborne geophysical data and continues to employ over 100 people in offices worldwide.

Aeroquest's present is focused on further expanding and developing our technologies and services. Together as a group, Aeroquest Surveys in Toronto, UTS Geophysics in Perth, Australia, and Geophex, Inc. in North Carolina, we are working to advance our systems, our technologies, our standards, procedures and our teams so that we offer the highest quality and service. We are proud of our technological diversity - proud to be more than most and supply a suite of specific tools which are each focused on their own exploration expertise. From a high resolution magnetic gradiometer to the helicopter-borne AeroTEM system to our frequency domain EM systems, the strength of Aeroquest's product offering is in its diversity and the ability to customize the survey systems and parameters to match the project requirements.