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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.
November 30, 2016
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
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 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 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
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 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
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...
As the planet's easy-to-find petroleum resources mature, deep offshore exploration and production lead the trend to the more difficult and challenging regions. Eni is one of a handful of leaders.
by Graham Chandler on June 4, 2012 expertise
Peak Oil theories aside, it’s no secret that the world’s easily-found petroleum reserves have mostly been discovered already. And as the planet continues to consume at the rate of nearly 1,000 barrels a second they are depleting. Exploration companies are pushing further into frontiers where environments are harsher, or were hitherto limited by technologies of the day.
The International Energy Agency predicts that oil will continue its dominance of the world energy scene well through 2035. By then, the organization projects, daily global consumption will have increased 18 percent to 99 million barrels per day. There will probably be enough to go around, but it’s ever-increasingly located in more expensive and complex frontier locations. So that’s where the exploration is trending.
New technology such as horizontal drilling and multistage fracturing is already unlocking vast new production levels from fields long abandoned as uneconomic—North America’s Bakken formation for example, which is expected to soon be producing a million barrels a day. These ‘tight’ and shale plays are skyrocketing in countries around the world and will help advance world production numbers. But it’s the frontiers where the big new elephant fields are being discovered.
Leading the new frontier exploration trend is the deep and ultra-deep offshore: the east coast of South America, the east and west coasts of Africa, and the Gulf of Mexico for example. Brazil is reported to have nearly 48 billion barrels of oil in water deeper than 600 meters. One field alone—the Lula—holds probably 6.5 billion barrels. Africa’s offshore west coast is where the world’s most active deepwater fields are found—primarily Angola and Nigeria.
The Gulf of Mexico, with more than 3,400 offshore production facilities, has been producing for decades. But further out, 300 or so kilometers from shore, the water is deeper and the geological formations are older. Esteemed energy research firm IHS CERA has suggested there’s nearly 13 billion barrels of recoverable deepwater oil out there yet. And already Shell’s Perdido production platform is on location producing from deposits 2,400 meters below the surface.
Knowledge of these deposits’ existence has been around for some time. Geological theory suggested the reservoirs were out there in sedimentary units past the offshore deltaics and into the turbidites. But the technology to explore and produce them wasn’t.
Holding back seismic exploration was largely the presence of massive salt layers which can be over two kilometers thick, laid down millions of years ago as ancient oceans evaporated. These high velocity media, with strong lateral velocity contrasts, induce such intense bending in the seismic waves that lots of the reflected energy can’t be recorded. This creates problems especially in the imaging of the salt flanks and in the formations below salt.
Leading the technological frontiers that have been unlocking the ‘salt barriers’ and making the discoveries possible is a handful of world companies. One who has developed the expertise is global player Eni.
Luca Mapelli, Potential Data Team Leader at Eni, explains how progress was made in seismic modeling that led to the breakthroughs. “First you search for easy targets, then when you need to increase the reserves you start looking for difficult targets,” he says. As these targets became the deep offshore, improved seismic processing capabilities were coming to the fore over the past decade, which opened up ways of looking beneath salt layers. “Explorers were able to better look beneath salt,” he says, “which still poses imaging difficulties, but less than before.”
Those advances included better processing through PSDM, RTM and better data gathering using WAZ, MAZ, and coil shooting says Mapelli. PSDM, or Prestack Depth Migration, is a model-based seismic imaging methodology. Compared to conventional time migration image processing, which assumes that seismic waves are propagated in straight rays, PSDM is pricier and slower but the payoff is more precise determination of reservoir structures. RTM, or Reverse Time Migration, can boast simplicity and superior imaging quality by using a full solution 2-way wave equation—it makes no approximations limiting the direction in which seismic energy can travel. WAZ (wide-azimuth), MAZ (multi-azimuth) and Coil shooting are advanced acquisition techniques aimed at addressing the illumination problems inherent in traditional narrow-azimuth marine seismic.
Coil shooting, used in exploration for deep offshore fields, consists of streamers towed behind a ship on spiral routes rather than on the traditional regular geometric grids. It provides full azimuth coverage of the targets allowing more detailed imaging than conventional techniques, and the data acquisition rate is faster compared to other multi azimuth techniques such as MAZ or WAZ.
While these advanced techniques are now indispensible in the deep offshore arena, there’s much more to it. For consistent success, integration of techniques and methodologies has become paramount. “A new approach to exploration has to be developed with a higher integration, at all stages, of different disciplines,” says Mapelli, “such as seismic reflection and gravity modeling, both inverse and forward. Only such synthesis improves our ability to constrain non-unique results predicted by theory, allowing for solutions that are distinct and robust in practice.”
“I could never stress too much the necessity of close integration between seismic and gravity data interpretation,” he says. “It should not be intended as a simple sharing of results, but as a new working approach where each discipline drives the other.”This is possible because seismic velocity (the basic property measured by seismic methods) and gravity share a common factor: density.
He explains that, as seismic velocities depend on elastic parameters and density, gravity inverse modeling could help in the definition of a density volume that could drive the definition of the seismic velocity volume, which is an essential part of the migration process in PSDM. The link between velocity and density is based on empirical relations that are more reliable if statistically controlled by well logs, i.e. sonic and density logs.
“During the interpretation phase, both gravity/magnetic data and seismic data could be used together to derive a unique geological model,” continues Mapelli. “The contribution of gravity data is more important wherever seismic data encounter imaging problems such as the presence of thick salt, gas hydrates, basalts etc. The higher the initial uncertainty is, the greater the value of a gravity/magnetic and seismic integrated approach will be.”
Mapelli uses Geosoft software for data integration, as it allows processing of potential data in a unique environment, and the ability to load other data such as seismic and wells to better constrain the interpretation process, he says. “The drill plotting capabilities help with the integration of gravity data and well data. When available, well data can give a strong constraint on the interpretation.” GM-SYS modeling capabilities, 2D as well as 3D, provide an easy way to check the consistency of a seismic interpretation, he adds.
These integrated techniques played an important role in the greatest discovery of Eni’s exploration history: the massive gas field in the Rovuma basin offshore Mozambique, which the company reported was “beyond expectation”. Exploration wells in the Mamba South showed up to 22.5 tcf, Mamba North 7.5 tcf, and Mamba North East 10 tcf; for a total of up to 40 tcf of gas in place. These are in waters 1,800 metres deep with overall well depths of 4,500 metres, “Exploration success was boosted by the application of proprietary technologies in the area of seismic mapping,” states the company’s 2011 Annual Report.
Gravity data acquired together with seismic data played a key role in the processing and interpretation says Mapelli. “The gravity dataset helped in the definition of the main depocenters, especially the isostatic map which clearly shows the thickest part of the sedimentary section,” he explains. “Other elaborations helped in the enhancement of the anomalies thus providing a better view of the structures affecting the area. A 2D modeling along selected profiles allowed us to fine tune the geological model with a sequential adjustment of the initial model until the misfit error fell below a predefined threshold.”
It has been an exciting proof of Eni’s expertise and technology. The company plans eight more wells over the next two years to monetize Mamba’s reservoir potential. For other companies, there are still thousands more square kilometres of offshore to explore. “Even the big salt provinces of west Africa, Gulf of Mexico and Brazil should be investigated in even greater detail and depth,” says Mapelli.
Development and enhancement continue, but so do new challenges. “While great improvements have been achieved in seismic imaging as well in potential data methodologies, the way forward is to improve the inversion methodologies for seismic data as well as gravity/magnetic data,” says Mapelli. “A real 3D joint inversion between gravity and seismic is the Holy Grail. Passing from a cooperative inversion to a joint inversion is the real step forward to get a unique geological model that satisfies the available data.”
The advances are paying off handsomely for many companies; one winner has been explorers’ reduced per barrel finding costs. Although exploration costs dwarf typical onshore per well figures, the sheer size of the deep offshore discoveries reduce the per barrel numbers. Brazil’s deep offshore Santos Basin for example yielded 30 billion barrels discovered with just 32 exploration wells.