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by Virginia Heffernan on December 11, 2013 expertise
Despite a steep appreciation in exploration spending over the past decade, the number of greenfield discoveries is falling every year. Narrowing this gap will require harnessing the power of big data and cloud computing, according to a presentation by Rio Tinto’s exploration chief Stephen McIntosh at the International Geophysical Conference in Melbourne.
“In a lot of cases, we have the data but we haven’t got the most out of it because of time constraints and our ability to find or “discover” this data,” Amanda Butt, McIntosh’s colleague and former manager of exploration and geophysics, said in a follow-up interview with Earth Explorer. “Now that we can do things more quickly, and efficiently we can get more effective information out of the data.”
Developing key geophysical systems with the ability to map and integrate geology is a focus for Rio Tinto. Geophysics has contributed significantly to nine of the 16 greenfields discoveries Rio Tinto has made since 1996, including most recently discoveries at the La Granja copper project in Peru. Copyright © 2009 Rio Tinto
Geophysics, in particular, has become an increasingly important exploration tool as the depth of the average discovery moves from close to surface in the 1950s to hundreds of metres deep. Indeed, geophysics contributed significantly to nine of the 16 greenfields discoveries Rio Tinto has made since 1996, including the Diavik diamond mine in Canada and more recently at the La Granja copper project in Peru.
In the 30 years previous, just a few of the company’s many finds had a significant geophysical component (e.g. the Elliot Lake uranium camp in Canada, the Parogominas bauxite deposit in Brazil and the Rossing uranium mine in Namibia).
Rio Tinto believes that geophysics will become an even more important discovery tool in the future with better collection, storage and processing of petrophysical data. “Geophysicists could do their jobs much more efficiently if they had access to quality petrophysical data,” said Butt. “But it’s not as routinely collected or as well organized as geochemical data tends to be.”
One way to cut down on the amount of time and effort required to transform petrophysical data into a reliable visualization of the subsurface is to use 3D inversion models.
Until recently, the use of 3D inversion – which gives explorers a snapshot of the most likely distribution of physical properties under the surface – was limited by computing power and a requirement for highly specialized knowledge. Inversions took days, sometimes weeks, to complete, and introducing physical constraints was problematic. But the rise of cloud computing and advancements in the technology have made the technique much quicker and far more accessible.
At the geophysical conference in Melbourne, McIntosh referenced two separate techniques that accelerate the inversion process: AMIRA International’s P1022 project and Geosoft’s VOXI Earth Modelling. The former research project, led by Peter Fullagar of Fullagar Geophysics Pty. Ltd., converts EM data into magnetic 'moments' before inversion whereas Geosoft’s solution is to harness the computing power of the cloud for inversion.
“A lot of EM data has been collected, but historically it has been quite difficult and time consuming to invert it, try to turn it into a geological model, or constrain it in various ways so that the inversion makes sense considering what we know about the geology,” said Butt. “Ideally, you’d run a number of inversions to test various scenarios, and now we have the ability to do that quickly.”
She said the company has invested in the Geosoft VOXI suite of software services and is encouraging its geophysicists - who have traditionally dismissed inversion because of its complexities - to use 3D inversion on a more routine basis in their quest for new orebodies.
In addition to sponsoring collaborative R&D projects, such as AMIRA’s 3D inversion initiative, that are designed to improve discovery rates, Rio Tinto has its own portfolio of exploration research initiatives.
Eliminating the noise associated with geophysical exploration techniques is an important component of the company’s in house efforts. For example, Rio Tinto believes it will soon be able to remove aircraft noise from its VKI gravity gradiometer to better detect signals in the earth of just 1 Eö per hertz of bandwidth, an achievement McIntosh equated with an archer in Rio de Janeiro trying to shoot an arrow into a 10 cm bulls eye in Melbourne.
Rio has been working on the gravity system in collaboration with the University of Western Australia for the past 20 years. The technology has recently undergone extensive testing, including flight trials, in order to determine its effectiveness in finding those “needle in the haystack” deposits that elude other systems.
“In the future we need to improve on the techniques that we already have to eliminate noise and make them much more accurate so that we can be confident that what we are mapping is the geology and not instrument noise,” said Butt.
Deposits may have become harder to find in recent decades, but by eliminating instrument noise, making 3D inversion an integral part of the exploration process and harnessing the unprecedented computing power of the cloud, Rio Tinto aims to see what is currently hidden.