The people, science and technology behind discovery

Subscribe to the Magazine

Get new articles sent directly to
your mailbox.


Join the network

Twitter Updates Group Forum

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

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...

November 9, 2016

International Volcano Scientists Unite

For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...

October 4, 2016

USGS Assesses Mineral Potential for Sagebrush Habitats in Six Western States

USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...

October 3, 2016

Uganda Targets Up to U.S.$100 Million for Mineral Exploration

Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...

September 9, 2016

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...

September 1, 2016

Scientists take to the skies to track West African pollution

Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...

August 17, 2016

New IGS Xplore prospectivity maps for Botswana

International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.

August 11, 2016

NexGen Makes New High Grade Discovery

NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...

August 10, 2016

Rampion UXO Disposal to Take Place This Week

E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...

August 9, 2016

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...

August 8, 2016

Northern Shield Identifies High Quality VTEM Targets at Séquoi

Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...

August 3, 2016

Rio Tinto tailors big data drive to copper

Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...

August 1, 2016

Tetra Tech Awarded $200 Million Navy CLEAN Contract

Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...

May 3, 2016

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...

April 11, 2016

Medgold Resources: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...

April 8, 2016

De-carbonizing our energy sector

Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...

March 15, 2016

N-Sea Expands into the French Offshore Wind Industry

Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...

March 9, 2016

PDAC 2016 Convention Exceeds 22,000 Attendees

Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...

March 3, 2016

6 Alpha Launches EOD Contracting Division

6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...

When seismic isn’t enough

Interview with Dr. Michal Ellen Ruder, Wintermoon Geotechnologies Inc on the use of gravity and magnetic methods for Oil and Gas exploration.

August 6, 2010

1. Under what conditions will gravity methods outdo seismic? Why?

Seismic data quality is not uniform in all geologic settings. Due to their elastic properties, some rock lithologies do not readily transmit acoustic energy.  As a result, seismic signal can be greatly attenuated, providing little or no seismic imaging below these acoustically-challenging horizons. If there is a significant lateral density variation below the problematic acoustic horizon, gravity can provide unique information about these rocks.  Gravity is not negatively impacted by rock elastic properties.

Another common imaging problem for seismic data is a near-vertical fault or interface (like a salt or shale diaper). Seismic signal is typically scattered by these interfaces. In contrast, both gravity and magnetics have their best imaging at vertical interfaces across which lateral density or magnetic susceptibility contrasts exist.

2. In what situations are gravity methods absolutely indispensable if you want results?

Gravity methods are vital for providing an independent corroboration of total volume and shape of salt when investigating sub-salt hydrocarbon potential. Seismic data quality can be significantly improved when we use gravity modeling results to improve and refine our seismic velocity model of the base of salt. This result is fed back into the seismic pre-stack depth migration processing to provide an improved seismic image of the sub-salt horizons’ geometries. Ultimately, this leads to more successful prospecting. We are presently using this approach in salt-prone basins offshore West Africa, South America, North America, and northern Europe.

3. Can you describe some cases where seismic and gravity methods complement one another?

Gravity is correctly characterized as a ‘low-resolution’ geophysical exploration tool. Without constraining information, a gravity model can be modified in an infinite number of ways in order to match the observed gravity signal. Seismic, well log, and other geologic data provide critical constraining information for gravity models, limiting the degrees of freedom of our modifications and enabling us to produce a meaningful, constrained earth model that is consistent with both gravity and seismic datasets.

4. What techniques have you personally developed or enhanced?

At Wintermoon Geotechnologies, we use a multi-faceted approach to interpretation. We work hard to identify and separate ‘regional’ and ‘residual’ signals within the observed gravity and magnetic datasets using our state-of-the-art Fourier-based 2D filtering routines. We have pioneered the construction of complex, geologically constrained 2D and 3D forward and inverse models. We construct models which incorporate geometries and physical properties derived from all available geologic and geophysical data, and we then invert the observed gravity and magnetic data to gain further insight into the geologic question at hand. Our 3D forward and inverse modeling approach has been successfully used in prospect evaluation projects in the Gulf of Mexico, offshore Brazil, and offshore West Africa.

5. Gravity/magnetic methods used to be used mainly to tell an explorer where to best place seismic. Nowadays you’re advocating its use as complementary and integrative to seismic as well. What has caused the shift?

Grav/mag data quality has improved significantly since the 1980’s. Not only can we acquire data more quickly now, but also our data resolution is much better and we can now resolve more subtle (lower amplitude and shorter spatial wavelength or high frequency) perturbations in both the gravity and the crustal magnetic fields. This improved resolution now allows us to imagine very small-scale and shallow lateral variations in density and magnetic susceptibility. These are often associated with the hydrocarbon play itself. Modern grav/mag surveys can now provide a set of observations that is more directly associated with hydrocarbon play character, in addition to the ‘traditional’ regional information for which we have long used potential field data.

6. What has been the hottest development in the past two years with respect to using grav/mag in oil and gas exploration?

We have two areas in which recent significant advances have been made. These include, in acquisition, airborne gravity gradiometry which provides a rapidly acquired, high-resolution image of local gravity anomalies, and in software development, improved 3D inversion algorithms for sophisticated gravity and magnetic earth models.