The New Frontier:
Exploring for Oil with
Gravity and Magnetics
Get new articles sent directly to
Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.
August 17, 2016
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 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
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
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 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 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 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
This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...
April 12, 2016
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 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
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
Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...
March 26, 2016
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
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
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 Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...
February 10, 2016
Canada's top uranium producer has a significant new discovery nearby to one of its largest existing mines...
February 9, 2016
NexGen announces further results from its on-going six rig 30,000 m winter 2016 drill program on its 100% owned Rook I Property in the Athabasca Basin, Saskatchewan...
February 9, 2016
Rio Tinto is opening its "vast troves" of exploration data to junior explorers in the hopes they will help sift for opportunities and supply ideas and labour...
February 8, 2016
The Botswana Geoscience Institute is launching a Geoscience Portal...
February 8, 2016
You just got your IRS tax refund and now you're presented with some cash to go out and buy one of a kind minerals and fossils from your local...
February 5, 2016
Dong Energy makes final investment decision on 1.2-gigawatt project that will power more than a million UK homes...
February 4, 2016
February 2, 2016
These high-grade mines will soon start competing with gold mining's industry leaders ...
January 25, 2016
In sharp contrast to the grim medium-term prognosis for the Canadian oilsands, Exxon Mobil Corp. is predicting sunnier times for bitumen in the decades ahead...
January 23, 2016
At a contaminated furniture factory site in North Carolina, a reconnaissance magnetic survey was conducted toward the end of a Phase 2 investigation ...
By Carmela Burns
Since graduating from Purdue University in 1981, Geophysical consultant Mark Longacre has been dedicated to the field of Oil and Gas exploration, specializing in gravity and magnetics. He's had direct involvement in over 1,000,000 line kilometers of high-resolution aeromagnetic (HRAM) data acquisition, processing and interpretation.
For the past 20 years, Longacre and his geophysical consulting company MBL Inc. have been providing clients with maximum insight through fully-integrated geological and geophysical solutions to Oil and Gas exploration. The main objective: risk-reduction and prospect enhancement through a better understanding of the subsurface geology.
Longacre credits his success to the fact that he has managed to stay small, focused and closely connected to all aspects of his client's projects. "I do most of my projects on site in my client's offices. Working side by side with the seismologists, basin petroleum systems people and the structural geologists, I become a member of the team. That's one of the reasons I am as successful as I am."
In recent years, Longacre has seen an increased interest in the use of gravity and magnetic methods with an emphasis on an integrative approach to projects. It's an approach that fits well with his team philosophy. "From an exploration sense, I'm no longer a geophysicist working remotely on one specific piece – I'm part of a team contributing to a whole understanding of the project."
Integration was core to uncovering critical new knowledge on the Earth's crustal structure in his recent research of the Eastern Mediterranean Basin (EMB). "The Eastern Mediterranean project is a classic example of integration," says Longacre."We were able to collect all the data we needed—not just gravity and magnetic data but ocean bottom seismograph (OBS) refraction data, and very long offset reflection data."
He says the integration of all the geological and geophysical data enabled them to better define the crustal structure, which was key. Although much had been published on the hotly debated and complex EMB structure, it had remained poorly understood and suffered from diverging opinions among geologists. Obvious seafloor magnetic anomalies were lacking, making it difficult to effectively map the distribution of oceanic crust.
Comparing their final model with the initial input profile which was based largely on existing published data, they noted several major differences. For example, depth to the top of the oceanic basement and the thickness of the overlying sedimentary section is greater than that first modeled, crustal thinning across the continental margin beneath the onshore and near-shore portions of the Nile Delta is higher than initially constructed, and some previously undetected changes in geometry of the MOHO (boundary separating the Earth's crust and mantle) were found.
Longacre and his associates, together with researchers from BP Egypt Exploration and the National Oceanography Centre in Southampton, UK, shared their EMB research findings in a presentation at the EGM 2007 International Workshop held last year in Capri, Italy. It was well received, says Longacre. "Structural geologists and petroleum technologists were able to come up with a new interpretation of how and when the Eastern Mediterranean Basin actually opened, and we discovered that the EMB opened in a completely different way than we previously thought."
This discovery provided new insight on the direction and age of the initial rifting, crustal structure and sediment thickness. And it led to new understanding of the basin heat flow, maturation of source rocks and hydrocarbon migration pathways.
All this information has enabled exploration decisions to be more defined. And, since the project was completed, Longacre notes there has been substantial drilling activity and exploration success with significant discoveries on the Offshore Nile Delta in Egypt.
"There were big faults that we couldn't understand," says Longacre. "But once we understood how the basin actually opened, we were able to achieve a better mapping of the tectonic elements. This has all helped to focus exploration in certain areas."
For Oil and Gas Explorers, knowing where to focus is critical. "The cost of a frontier exploration dry hole is 100 to 120 million dollars and costs are going up," says Longacre. "That's a lot of money. Spending a fraction of that to really make sure there are no surprises when you're ready to drill makes good sense."
Interpreted distribution of crustal type and key basement fabric within the EMB. 1
1 Peter Bentham, Ibrahim Hanbal, James Cotton, Mark Longacre & Rose Edwards 2007. Crustal structure and early opening of the Eastern Mediterranean Basin: key observations from offshore northern Egypt and the Levant (EAGE 2007 Abstract)
As explorers look at deeper, more remote and more costly targets to meet global energy demand, proven, low-cost techniques like gravity and magnetic are being brought in earlier in the project cycle to minimize the risk of conducting expensive seismic investigation in potentially less productive basins.
Moreover, several areas scanned decades ago can be re-examined utilizing higher resolution data and new techniques such as gravity gradiometry and satellite gravity. And software advances are enabling integration and interpretation of these data to levels unheard of a decade ago.
"There's definitely more interest and use of gravity and magnetic methods today," says Longacre. "The cost of exploration has risen dramatically and the end result is that Oil companies are making sure they look at everything." This includes a lot of previously unexplored areas of the world's geology.
"We're pushing the envelope geologically. We're going out and exploring in areas we've never looked at before. We're being brought in much earlier in projects and really high grade areas even before they shoot 3-D seismic."
It's also driven by stronger interest in the tectonic evolution of basins, adds Longacre. "We're more interested in the crustal aspects, like crustal structure and depth to MOHO, than ever before. These sorts of things can play a big part in how the basin formed, sedimentation rates, petroleum systems, maturation and paleo-continental margins. And gravity and magnetic methods are ideally suited to help answer these types of questions."
Being able to better integrate potential field data with the other kinds of geophysical and geological data has been key. "We're much more integrated than we've ever been," says Longacre. "With today's software and technology, integration from the gravity and magnetic world to the seismic world is a seamless one. Data and maps can be easily shared and used in GIS, petroleum systems software and seismic workstations."
Advances in technology have also provided the ability to turn things around much quicker, in hours instead of days. "Technology has enabled results 'on demand'. You're much more flexible, and able to turn in different directions based on what the data tells you," he says.
For his integrated consulting needs, Longacre is a dedicated user of Geosoft's Oasis montaj and GM-SYS software for processing, data integration, modeling, interpretation, and exploration analysis.
"Geosoft is still by far the best software for generating gravity and magnetic interpretations, and products that can be easily integrated into the seismic world," he says. "You can add your own tools and your own software with the powerful Geosoft GX toolkit. This means you can still differentiate yourself with software that other people don't have, and customize it to suit your needs."
And given that his clients use a variety of different technological platforms, Longacre notes that the main advantage is the seamless integration of the software. "I can process data, work on maps, and build the model in the same platform," he says. "I can generate something and send it knowing that in a few minutes, they can have it at their work station and on their screen."
Going forward, Longacre sees huge potential for gravity and magnetic methods to add more value as the Oil and Gas industry moves to more integrated exploration approaches.
"In general, the gravity and magnetic consulting community is full of talented people that are pushing the envelope," says Longacre "Gravity and magnetic methods have huge value, and as the integration continues, more and more value can be added. We're generating knowledge that others can run with and build on."