Helicopter time-domain electromagnetics can be of substantial value to pre-engineering and construction projects. This White Paper presents several real world examples of how and where SkyTEM data was used to quickly and economically create or revise geological models and reduce risk on geotechnical engineering projects.
The ability to reveal the availability and movement of groundwater can be a huge asset for countries and regions with the need to responsibly and sustainably manage their aquifers.
The SkyTEM method, specifically developed to map buried aquifers, is widely accepted globally as the principal technique for mapping water resources. SkyTEM is an innovative and technologically advanced airborne geophysical system capable of mapping the top 500 metres of the Earth in fine detail and in 3 dimensions. SkyTEM was conceived and engineered in Denmark, a country with a reputation for environmental care and R&D. SkyTEM helps geological organizations and government water agencies on seven continents unearth a wealth of information about their aquifers and aids in their understanding of how geology and mankind can affect, and be affected by, groundwater resources. The SkyTEM method has mapped water resources on a Galapagos Island, important agricultural areas in the USA, Australia, Africa and India, islands in the Caribbean and Indian Ocean and even Antarctica. Recognized for its ability to quickly and accurately map geology in fine detail, the SkyTEM method is also employed globally for mineral and oil & gas exploration as well as environmental and engineering investigations.
This white paper provides results from recent global water exploration projects – from finding new fresh water sources to identifying groundwater recharge areas, saline water encroachment and more.
Water is essential for life on earth. Two thirds of Earth’s surface is covered by water and oceans hold about 97% of all our water. In the remaining 3% of fresh, or non-saline water, groundwater provides us with 30% of all our drinking water while 68% is trapped in a frozen state. Less than 2% is available as surface water. This limited supply of available surface and groundwater is the main source of drinking water for the planet’s seven billion plus people. In recent decades as demand for water increases we witness falling water levels in almost all of the world’s wells, and many are beginning to run dry.
According to a recent NASA study one third of the Earth’s largest groundwater basins are being over-exploited. Twenty-one of the world’s 37 largest aquifers, in locations from India and China to the United States and France have removed water quicker than it can be replaced by rain and snow and their sustainability is at a critical point. (see http://go.nasa.gov/1G3fLIV). Depletion of water resources is an immediate and growing concern and is creating overwhelming challenges for the next generations.
Click here to download the entire white paper: Mapping Groundwater with SkyTEM
The SkyTEM system is an innovative and technologically advanced airborne geophysical system specifically designed to mapping water resources. This unique technology, capable of mapping the top 500 metres of the Earth in fine detail and in 3 dimensions, was conceived and developed in Denmark, a country with a reputation for environmental care and R&D.
SkyTEM has helped geological organizations and government water agencies on seven continents unearth a wealth of information about their aquifers and aided in their understanding of how geology and mankind can affect, and be affected by, groundwater resources.
Drillling boreholes is not enough for mapping water
In most parts of the world groundwater mapping is based only on one data source – drilling information. A 6 inch borehole represents less than one millionth of acre. This 6 inch borehole will provide precise information about the geology immediately in the vicinity of the hole, but any assumptions made about the surrounding geology is a leap of faith or at best a guess. Drilling boreholes can be expensive particularly when insufficient information is available to determine where to drill and how deep to drill for water. If a large area is being studied, budgets may only allow for limited drilling so selection of where to drill is crucial. Also, access to some areas can be difficult and expensive if the terrain is remote, rugged or heavily vegetated. Limited drilling is often the only option cosidered and low borehole density can result in uncertainties and low confidence levels in geologial interpretations and hydrogeological models.
The SkyTEM airborne method of mappping quickly and economically delivers accurate subsurface data from which location of and depth to aquifers can be revealed.
Read more about the SkyTEM method for mapping water resources in the brochure here.
Information presented in the report is the result of the Peace Project, a Geoscience BC-funded project focused on mapping and assessing groundwater in the Peace Region of British Columbia. The report presents data from a SkyTEM airborne electromagnetic (AEM) geophysical survey that was employed to map the hydrogeology in the Peace Project area.
The Peace Project was planned to deliver regional hydrogeological data through an integration of pre-existing data from shallow wells and 3-D seismic surveys with the results of an airborne geophysical survey. Airborne geophysics was considered an essential tool to provide more cost-effective and time-efficient coverage of a large area, than ground-based geophysical methods. The AEM system employed for the project was SkyTEM312FAST, a helicopter-borne TDEM system. The 8000 km2 area was covered in 43 days.
The objective of the AEM survey was to collect resistivity data from near surface to depths up to 300 m and combine this new information with prior data to 1) interpret potential Quaternary and bedrock aquifers within the area; 2) provide a map of the Quaternary–bedrock interface and thus Quaternary sediment thickness; and 3) generate a magnetic structure map of the basement. In general, it is expected that a joint interpretation of all geophysical data will help to determine optimal places for accessing and/or protecting the groundwater and finding non potable sources of water for energy sector use.
The AEM survey involved collecting over 21,000 line-km of data, covering an area of about 8000 km2.The airborne system used, SkyTEM312FAST, collected TDEM and magnetic data with an average speed of 118.8 km/h over the entire survey area. Preliminary data was delivered for quality assurance-quality control purposes every 48 to 72 hours to a third-party consulting firm. At the time of writing this paper, the final data and inversion results were still in the processing stage.
An important component of the airborne survey was communication and outreach with Treaty 8 First Nations and
communities within the survey area. Flights were planned and co-ordinated daily to avoid disturbance of First Nation cultural events, farmers and ranchers in the area. Through discussions with the Blueberry River, Doig River and Halfway River First Nations, the original survey area was expanded to include areas of interest over sections of their traditional lands. Additionally, an area around Fort St. John was flown in response to a request from the Peace River Regional District
Based on the raw data presented above, data-inversion was carried out using the laterally constrained inversion (LCI) method developed at Aarhus University, Denmark. The LCI technique is a relatively new inversion methodology whereby field data are filtered then modelled against a subsurface layer structure that is constrained laterally on a number of chosen model parameters (including layer conductivity and layer thickness).
The inversion results show very detailed structures in both the near-surface and deeper layers. Higher resistivities in the northwestern corner at all depths correlate with the presence of bedrock. High values of resistivity present in the shallower levels, indicate the presence of coarser material, such as sand, gravel and till, near the surface. The deeper levels are dominated by lower resistivities, which indicate the presence of more clay-rich material, till, water saturated sediments and/or bedrock shale and siltstone.
The report including data and results can be downloaded from Geoscience BC’s website here: http://www.geosciencebc.com/i/pdf/SummaryofActivities2015/SoA2015_Brown.pdf
The on-going development of SkyTEM MultiMoment® TEM systems has been driven by specific exploration objectives. First, to increase the power and depth of penetration. Second, to reduce the noise level and enhance detection of subtle contrast at depth. The result of a 5 year development program, SkyTEM516 has recently demonstrated its accomplishment of these objectives over the Caber Deposit in Québec, Canada. SkyTEM516, with a transmitter area of 536 m2 and 16 turns, is capable of delivering a dipole moment of more than 1,000,000 NIA. In addition, a unique receiver design has been engineered to reduce the noise level by a factor of 20.
The Caber North deposit is particularly suitable for testing a helicopter-borne EM system’s signal-to-noise as it is a challenging target and one that conventional ground EM systems have difficulty detecting. The deposit (1.3 Mt @ 4.0% Zn, 1.7% Cu) is buried under more than 300 meters of conductive overburden. SkyTEM516 and SkyTEM512 (launched in 2014) are both proven to successfully detect the Caber North deposit. Detection of this target is difficult because its response ranges from 2 to 10 fV/Am4 where 1 fV=10-15 V. Hence, detection of Caber North and similar targets requires a dipole moment in the range of 1,000,000 NIA and, above all, an exceedingly low noise level.
The SkyTEM516 has an un-normalized target responses range between 2-10 nV/m2. Therefore, in order to detect this target the noise level must be markedly lower than 0.5 nV/m2. Few airborne EM systems are capable of achieving this since systems with a high dipole moment typically have a corresponding high noise level due to limitations of the receiver system. As a result, many systems are incapable of detecting the Caber North Deposit due to an inferior signal-to-noise ratio.
All SkyTEM MultiMoment® systems are capable of mapping the near surface concurrently with depth. A range of systems is available to provide solutions for varying exploration objectives.
Download the brochure with test results here: SkyTEM516 over Caber Deposits.
If you would like to see the entire test results, please send an email to CEO Flemming Effersø, firstname.lastname@example.org, with your name, organization and email address. We will respond to you within 1 or 2 working days. You will be asked to sign a confidentiality agreement before you receive link and password to an FTP site.
Read two papers regarding SkyTEM used for geotechnical Engineering.
Presented at ASEG-PESA in 2013 by NGI and RockSense Geosolutions.
They investigate an active rock slide in Western Norway with ground- and airborne resistivity mapping to ultimately find weakness zones and sliding planes embedded in crystalline bedrock. Based on a successful airborne electromagnetic (AEM) demonstration survey they conducted a total of 1,600 profile meteres of ground resisitivy Measurements to confirm AEM anomalies, to gain precise 2D geometries and to link conductivity anomalies with geology.
Presented at Near Surface Geoscience in 2014 by NGI and Queen’s University.
A new road segment is being planned northeast of Norway’s Capital city, Oslo. In this context, knowledge of sediment thickness is vital, as is information about occurrence and extent of highly sensitive marine clay (so-called quick clay).
Airborne EM Measurements were donducted to provide information of depth to bedrock/sediment thickness between drilling sites and guide the further drilling program. AEM data indicate a variable bedrock depth with a general trend towards shallower bedrock in the northeastern part of the investigation area. Quick clay is not easily identified in the AEM data, but some possible occurrence agree well with the results form the drillings.
The objective of the whitepaper is to summarize the efforts of SkyTEM development team to extend the capability of SkyTEM time-domain electromagnetic systems in order to acquire multi geophysical data. We are also proud to introduce unique geophysical system capable to acquire simultaneously dual-moment time domain electromagnetic, magnetic and gamma-ray spectrometry data at the same height level.
The system is designated for different applications where it is required to acquire multi-geophysical with high resolution and low terrain clearance. This is possible because we have found way how to place all sensors on the same carrier and acquire all data without to interfere each other. The key of the success was to use a concept of light-weight robust spectrometers and full spectrum analysis method as an alternative to heavy big volume spectrometers placed on aircraft and conventional windows method. Certainly we can offer the big volume NaI spectrometer concept accepted as industry standard, however we believe that the light weight spectrometer concept may provide better data resolution.
Download the whitepaper Whitepaper – Combined GRS Surveys.
SkyTEM surveys has conducted a survey of Graphite One Resources’ Graphite Creek property in Alaska, USA. The SkyTEM304 system successfully mapped conductive bodies coincident with the extent of known graphite mineralization. SkyTEM also detected a significantly larger trend of conductors that led to the discovery of new high grade graphite mineralization.
…the system remains open along strike and depth as defined by the geophysics and mapping, conrfirming the strength and continuity of this deposit.
President and Director
Graphite One Resources
Download the case study Graphite_Exploration_Case_Study.