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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

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...

A Marathon Record

Innovative integration of gravity and magnetic methods help Marathon Oil Corporation maintain world leadership in oil and gas exploration

By Graham Chandler

When Pat Millegan came to Marathon Oil Corporation in 1983, he brought with him a keen interest, and experience in gravity and magnetic methods for oil and gas exploration. Now with 32 years of industry experience under his belt, there's little the company's Geoscience Consultant, Subsurface Imaging doesn't know about the techniques —the whole gamut from planning and specifying surveys, quality control of the data and its processing through to integrated interpretation; all using the latest innovations.

It's made him a valuable team asset for a company like Marathon, which has a strong record of success in exploring for oil and gas around the globe. One of the oldest oil companies in the industry, Marathon was established in 1887. Headquartered in Houston, Texas, Marathon is the fourth largest integrated oil and gas company in the US, with revenues over US $65 billion in 2007.

Marathon's exploration activities focus on adding profitable production to existing core areas – the U.S., Equatorial Guinea, Libya and the North Sea (UK and Norway) – and developing potential new core areas in Angola and Indonesia. The company has long been active in Libya's Sirte Basin, one of the most prolific oil and gas producing areas of the country; which still contains sizable undeveloped reserves. Marathon's concessions there currently produce about 345 thousand barrels of oil equivalent per day on a gross basis and encompass almost 13 million acres. Marathon holds a 16.33 percent working interest in the Waha concessions in Libya.

Behind Marathon's record of success is a focus on realizing the full potential of their upstream assets through knowledge integration and technological innovation. In the oil and gas business the key to optimizing production and resource development is quick and accurate description of reservoirs. Marathon's expertise in reservoir characterization often begins with seismic imaging, but it emphasizes integration of all geoscience, petrophysical and engineering data into fully integrated interpretations.

An important part of their integrated approach is effective use of potential fields methods. The benefits of such an approach are higher success rates in discovery, drilling and production activities and Marathon's record illustrates that.

Gravity and magnetic methods have proven to be effective in many regions of the world, particularly in sub-salt areas. Without the use of these data, prolific sub-salt traps would be much more difficult to locate and image. Using seismic alone, the high velocity salt layer absorbs and scatters the energy, distorting any picture of prospective reservoirs lying beneath the salt layer itself.  Used in a tightly integrated fashion, potential fields methods can supply a better estimate of the salt shape and size, which is then used to improve the sub-salt seismic imaging.

Offshore West Africa, the Gulf of Suez, the Red Sea, and of course the Gulf of Mexico are all regions where gravity and magnetics have enhanced exploration in this way.  Though generally considered to be complementary to seismic, in some cases drilling decisions have been made on the basis of gravity and/or magnetics alone particularly when seismic imaging is challenging.  In one case, aeromagnetics has been credited with the discovery and delineation drilling of Ras El Ush Field in the southern Gulf of Suez in the 1990's.  Today, the integrated workflow used in the Gulf of Mexico salt interpretations is an integral part of decision making for leasing and drilling.

Sub-salt imaging is a prime example of where these methods excel, but not the only one, says Millegan. "Gravity and magnetics are doing well with the current resurgence of exploration in general," he says. "Exploration is becoming more difficult, entering remote areas and areas of poor seismic imaging."

Working with the techniques for better than three decades, Millegan has seen their value and potential over the years. "Gravity and Magnetic techniques have never ceased being valuable to the exploration effort," he says. "As exploration in general increases at increasingly higher costs, gravity and magnetics' proven track record for risk reduction and integrated G&G [geological and geophysical] analysis has kept it in demand."


Knowledge integration and technological innovation have kept Marathon at the leading edge of oil and gas exploration.

Integrating them with other data streams these techniques have played, and continue to play, an important part in Marathon's longstanding expertise and successes in accurate reservoir definitions and delineations. "Integrating gravity and magnetics with seismic, each measuring different, but related rock properties, offers more robust geologic interpretations," explains Millegan. "This provides management with the best information available to make leasing or drilling decisions."

Management and integration of gravity and magnetics is just part of the team effort, but it's a critical part. "My success is measured by the success of the team with which I am working," says Millegan. "Often there is a direct cause and effect, where gravity and magnetics offer something direct, such as the calculation of salt mass, or the depth and extent of a structural block, or the presence/absence of volcanics in the section." Or, sometimes the contribution is less concrete, he says, like perhaps a regional geologic/tectonic analysis that helps the team integrate various disciplines, thus helping to focus their decision making.

It's all kept Marathon at the leading edge of oil and gas exploration.

Use of gravity and magnetics with Marathon is increasingly impacting its technology needs. "We are busier than ever," says Millegan. Marathon added Dr. Neda Bundalo to their Subsurface Imaging team in 2007.  "Neda has allowed us to continue to offer high quality work in a timely fashion," he says."Our workload for gravity, magnetics and EM has doubled this year.  More now than ever we need our software tools to be responsive, integrated, and technically state-of-the-art. This is a huge challenge."

Millegan sees the use of potential fields methods in geophysics continuing unabated. "As the search for oil and gas gets more and more challenging and expensive in increasingly more difficult water depths and terrains, all geophysical tools must be applied to reduce the financial risk to the oil company," he says. "Many of us can argue that potential fields  geophysics has been under-utilized in our industry. Many have predicted the demise of potential fields geophysics in every decade. But we are still here and we are doing more rigorous and financially impacting work. We must continue to improve our skills and our tools to meet new challenges."