Georges Bank holds promise
Basin Awaits Lifting of Moratorium
Twenty years ago, AAPG member Tako Koning was the exploration manager for Texaco Canada Resources, and Texaco was poised to drill two exploratory wells on the Canadian side of Georges Bank, known as the East Georges Bank Basin.
The well locations were selected and the site specific geophysical surveys were completed when the Canadian and Nova Scotian governments jointly invoked a drilling moratorium – due to environmental issues – that would remain in effect until Dec. 31, 2012.
Koning has never forgotten this unexplored basin that got away – a basin that has remained in force majeure time warp with no industry activity for 20 years.
“I’m quite passionate about information sharing,” Koning said, “and rather than letting that information die, I want to give back the East Georges Banks information (to industry, academia and to the public-at-large).”
Graphic courtesy of Tako Koning
Koning, who was part of the program advisory committee for a recent Halifax conjugate margins conference, retired from ChevronTexaco in 2002 and now works in Angola as a consultant with Tullow Oil PLC.
The East Georges Bank Basin, however, still captivates his interest.
Koning presented a paper at the Halifax conference titled “Revisiting the East Georges Bank Basin, Offshore Nova Scotia – What the Explorationists Saw Two Decades Ago.” He has presented this paper (with Texaco’s approval) in various forms at international conferences nine times since 1988.
“There aren’t many undrilled basins in the world, and especially very few basins in the world – in such proximity to a large market – that have never been explored by a drill bit,” Koning said of Texaco’s lost opportunity.
“When you put it all together – the seismic and the structures – this is the kind of basin that you’d drill anywhere in the world.”
Clues to offshore potential are typically found in scenic outcrops, such as this spectacular view of the famous Triassic-Jurassic boundary at Five Island, Nova Scotia, Canada.
Photos courtesy of David E. Brown
Middle Jurassic pinnacle reef consisting of coralgal reef builders (up to 90 m thick) in the High Atlas Mountains of Morocco.
Photo courtesy of Tako Koning
Chances for Success
Koning assigned a 10 percent chance of success to the first series of exploratory wells that will test the play concepts developed in the 1980s by Texaco, based upon using the existing grid of vintage 2-D seismic data.
He acknowledged that the exploratory risks to success include the existence of source and reservoir rocks. These exploratory risks, however, may be reduced due to the existence of several new and significant discoveries in the adjacent Scotian Shelf, and technological breakthroughs in seismic data imaging, processing and mapping methods.
Georges Bank straddles the American-Canadian border. On the boundary’s American side, the West Georges Bank Basin has been under drilling moratorium since 1982. However, given recent political events in Washington, the West Georges Bank Basin may be reopened for oil and gas exploration.
Prior to 1982 American companies drilled eight dry holes in the West Georges Bank Basin, a minimally deformed basin – these wells tested stratigraphic targets exhibiting high amplitude reflectors.
Excellent strike view of a 33 metre thick barchan-type dune complex at the base of the latest Triassic Blomidon formation, Red Head, Nova Scotia. This succession overlays Wolfville formation fluvial sandstones and conglomerates and represents the transition from wetter to drier climatic conditions as evidenced by the upper flat-lying playa-lacustrine strata.
With the exception of one well, the wells failed to encounter source rocks, and were deemed to be “organically lean.”
“We (Texaco) never lost any sleep over those wells on the U.S. side,” Koning explained, “because there are two distinct sub-basins in Georges Banks.”
A prominent Paleozoic basement feature called the Yarmouth Arch separates the West and East Georges Bank basins.
The basin geometry – and the oil and gas potential, according to Koning – is distinctly different on the Canadian side, where there’s a lot of structural “action” in the form of large, down-to-the-basement listric faults, salt diapiric structures and a significant reef trend that’s correlated to the Late Jurassic age Abenaki hydrothermal dolomite reservoirs on the Scotian Shelf at Deep Panuke.
What’s Next?
According to Koning, geological curiosity has inspired his 37-year-long career in the oil and gas industry.
This spectacular view is of the famous Triassic-Jurassic boundary at Five Islands, Nova Scotia, Canada. To the left is a complexly-faulted and highly deformed block of Jurassic CAMP basalts of the North Mountain formation. To the right it conformably overlays the Triassic Blomidon formation playa-lacustrine mudstones with the Triassic-Jurassic boundary located within the light grey sediments under the basalt.
In 1992 he attended an AAPG-sponsoredgeology field trip led by John Warme to the High Atlas Mountains of Morocco, to lay his hands on the prospective reservoirs in the conjugate margin – interpreted reef and clastic plays from 2-D seismic – of East Georges Bank Basin in outcrop. He saw spectacular outcrops of the equivalent rocks that Texaco’s geophysicists had interpreted on the opposite side of the Atlantic Ocean, some 6,000 kilometers westward, offshore Nova Scotia.
In a 1983 report by the Geological Survey of Canada, the seismically defined prospects of the East Georges Bank Basin were estimated to contain mean recoverable gas reserves of 5.3 Tcf and 1.1 billion barrels of oil, with a high side figure of 10.8 Tcf and 2.1 billion barrels of oil.
Through historical mergers, the Texaco leases now belong to Chevron. In fact, almost close to 100 percent of the Canadian Georges Bank is currently held under exploration licenses that have remained in effect despite the force majeure conditions.
Koning is optimistic that the moratorium on Canada’s Georges Bank will be rescinded in 2013.
“It will be up to the people of Nova Scotia and the politicians to decide if the potential of the East Georges Bank Basin will be evaluated,” he said.
“Certainly my view is that oil and gas activities and fishing can co-exist successfully, as we see in many parts of the world such as the North Sea, Gulf of Mexico and the Grand Banks of Newfoundland.”
