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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.

News & Views

News Archive

February 25, 2015

NexGen Drills Best Angled Hole to Date: Discovers New High Grade Zone at Arrow

NexGen Energy Ltd. announced ongoing results from their winter 2015 drilling program at their our 100% owned Rook I property, Athabasca Basin, Saskatchewan...

February 24, 2015

Phase II drilling underway on Kootenay's La Negra

Kootenay Silver Inc. announced that camp upgrades are complete and Phase II drilling has now commenced on its La Negra Silver discovery, contained within the Promontorio Mineral Belt in Sonora, Mexico...

February 23, 2015

Explorer Speaker Series at the PDAC

Geosoft's Explorer Speaker Series at the PDAC 2015 includes presentations on Peregrine's Chidliak Project and Cameco's initiatives to increase efficiency and 'harvest time' through data organization…...

February 18, 2015

Largest Dam Removal in U.S. History Scientifically Characterized

The effects of dam removal are better known as a result of several new studies released this week by government, tribal and university researchers...

February 18, 2015

Exeter outlines the significance of its Caspiche Project water discovery

Exeter Resource Corporation has announced further positive results from the expanded water exploration drilling program for its Caspiche gold-copper project in northern Chile...

February 17, 2015

Earthstar Geographics Releases Arctic Ocean 15-Meter Satellite Imagery Mosaic

In response to the rapidly increasing demand for high quality geodata of the Arctic Ocean, Earthstar Geographics LLC has compiled a detailed satellite imagery mosaic of the entire region and released it in map projections optimized for visualizing the northern polar areas...

February 11, 2015

Geophysics and Geology together for Discovery: Geosoft at ASEG-PESA

Geosoft's program for the ASEG-PESA, February 15-18 in Perth, includes a workshop on practical geophysical workflows for resolving common problems in minerals targeting...

February 9, 2015

Pilot Gold Reports Final 2014 Results from Columbaz Discovery at TV Tower

Pilot Gold announced the final 2014 results from its third gold rich porphyry discovery at TV Tower, located 6.5 kilometres north of the Valley and Hilltop porphyries...

February 5, 2015

Coastal Gold finds the high grade

Coastal Gold has defined a high grade resource at its 100%-owned Hope Brook gold deposit in Newfoundland by developing a 3D model that has tighter constraints and focuses on higher grade drill results.

February 4, 2015

Non-seismic Geophysics

Finding Petroleum is hosting a half-day event on the role of non-seismic geophysical techniques. Are they coming of age? Reserve your space for this free event, being held in London, February 19.

January 27, 2015

Factors Driving 2015 U.S. Oil Output

Rig counts are a highly imperfect guide to future oil production but they are one of the few readily available statistics on oilfield activity so it is unwise to dismiss their importance entirely...

January 23, 2015

Will 2015 Break this ‘Dry Spell’ for New Discoveries?

Steve Todoruk, a broker with Sprott Global Resource Investments, explained in Sprott’s Thoughts recently why ‘juniors’ should look for new discoveries by drilling into the unexplored depths near existing mines...

January 20, 2015

Eni Wins Two Exploration Licenses in Norway

Italian oil and gas group Eni said on Tuesday it had won two exploration licenses in the Barents sea and in the North Sea in Norway...

January 9, 2015

WVU, USGS collaboration sheds new light on coal-cleaning chemicals found in the 2014 Elk River Spill

A collaboration between the U.S. Geological Service and West Virginia University has resulted in a better understanding of the chemicals that spilled into the Elk River in 2014, affecting the drinking water of 300,000 Charleston-area residents...

January 7, 2015

Precipitate's Phase 2 IP Survey Extends Ginger Ridge Chargeability Anomaly Additional 800 metres North

Precipitate Gold Corp announced results from its recently completed Phase 2 induced polarization ("IP") geophysical survey at the Ginger Ridge Zone within the Company's Juan de Herrera project in the Dominican Republic...

December 18, 2014

IGC's completion of Eastern Seaboard regional integrated interpretation package

Integrated Geophysics Corporation (IGC) announced today the successful completion their Eastern Seaboard regional integrated interpretation package. Designed for oil and gas companies needing a First Pass Look at the regional tectonics and structural trends for this new frontier...

December 10, 2014

Advances in base of salt and sub-salt imaging, Geosoft releases VALEM HPC inversion modelling

Integrated within Geosoft’s GM-SYS 3D Modelling software program, VALEM is an improved, interactive solution for sub-salt interpretation that resolves the base of salt from gravity data bound by the constraints of seismic modelling...

December 03, 2014

Petrobras makes deepwater discovery in Colombian Caribbean

Petrobras reported the discovery of a natural gas accumulation with the Orca-1 exploratory well drilled on the Tayrona block in the deepwater Caribbean Sea, 40 km offshore La Guajira, Colombia...

Harnessing the Power of Parker

April 29, 2010

Even with the dramatic advances in computation speed, the demands of the petroleum exploration industry to find more oil faster has grown exponentially. Geosoft’s Gerry Connard explains the advantages of using Fast Fourier Transforms (FFT) for gravity and magnetic modelling.

What research is the approach based on?

Robert Parker’s seminal paper published in 1972, The Rapid Calculation of Potential Anomalies, has led to a revolution in using FFT for gravity and magnetic modeling using ‘gridded’ data. Since then, a number of additional papers, including some by Parker himself, have extended and improved Parker’s original work. Richard Blakely’s 1995 book summarizes most of this development and provides some additional, related FFT algorithms for FFT-based gravity and magnetic calculations (such as Blakely’s ‘Earth Filters’).

What are the advantages of the FFT-based methods?

Parker describes in the introduction of his 1972 paper that the computation time for a model grid containing N points is proportional to N ln(N). For equivalent space-domain calculations on the same type of model, the computation time is proportional to N2. This difference is not so significant for small models. For example, to calculate the response of a grid with 100 points, the space-domain approach would require approximately 20 times as many calculations as the FFT approach. However, as the number of grid point increase, the ratio of the number of calculations in the space-domain approach compared to the number of calculations in the FFT-based approach increases rapidly. For a grid with 1000 points, the ratio is 144. For a grid with one million points, the ratio is 72,382. So if the FFT-based approach took one minute of compute time, the space-domain approach would take 50 days.

Are there disadvantages of the Parker method?

There are pitfalls in the FFT-based calculation approach, including but not limited to the problems of edge effects, periodicity, and the fact that the original Parker algorithm is based on the convergence of a Taylor-series approximation. With two decades of practical experience using the FFT-based approach, most of these problems have been solved or at least minimised. For example the “Earth Filter” algorithm does not need the Taylor-series approximation.

What are your future predictions?

The FFT approach continues to evolve. Two papers by Parker in 1995 and 1996 extend his method to compute the results on an uneven surface. This allows more flexible models that more closely resemble a real earth model which are more appropriate in many exploration scenarios. In 2009, a new paper published by Caratori Tontini and others describes how to use 3D FFTs for gravity and magnetic calculations that will likely lead to significant improvements in FFT-based methods. Although raw computing power continues to grow according to Moore’s Law, our computing needs are growing even faster. Explorers today are taking advantage of a wealth of detailed exploration data to build larger and more complex models with grid sizes often exceeding one million points. FFT-based methods will play an important role in tools for the utilization of gravity and magnetic data in large, detailed models.

In spite of the disadvantages of the computational speed of space-domain techniques, they will also continue to be important tools in the interpretation tool kit. Space-domain techniques are inherently more flexible than FFT-based techniques and more easily utilised for inversion schemes. One powerful approach is to use a hybrid technique that combines both FFT-based and space-domain techniques in a modeling tool. Cloud computing (such as using large banks of parallel processors at a remote site) is also likely to be part of our exploration computing future. This approach is already being used by companies like Microsoft and Google to bring amazing computing power to desktops around the world.

Gerry Connard is the Petroleum Industry Market Manager with Geosoft. Connard is a geophysicist with over 30 years’ experience in the exploration industry. He founded NGA, Inc. and developed gravity and magnetic profiling and modelling software – GM-SYS and GM-SYS 3D.