It started, as all great exploration stories do, on a very large scale. Nalcor Energy put together an exploration strategy in 2010 that began with a satellite oil seep survey covering 1.5 million sq km (580,000 sq miles) offshore Newfoundland and Labrador. This was followed by a large-scale 2-D seismic program from the tip of Labrador to the Canada/Greenland border and down toward Flemish Pass. Seabed coring also was undertaken.
But it wasn’t until summer 2015 that Nalcor brought in the big guns—a 3-D seismic survey using long-offset broadband acquisition technology. Early data from that survey became available in summer 2016, boosting the already considerable estimated resource potential to 25.5 Bbbl and 583 Bcm (20.6 Tcf), just in time for a licensing round in November 2016.
And the industry responded. The call for bids received almost $758 million in work commitments and lured three new companies—Hess Canada Oil and Gas, Noble Energy Canada and Delek Group—to the region. Sixteen parcels of land totaling more than 33,000 sq km (12,741 sq miles) was up for grabs, 13 of which are in the Eastern Newfoundland Region and three of which are in the Jeanne D’Arc Basin.
The survey covered the West Orphan Basin located within the area of the Canada-Newfoundland and Labrador Offshore Petroleum Board 2016 Eastern Newfoundland Call for Bids. It’s part of a longer term goal to assess the vast stretches of virtually unexplored territory belonging to the country.
“We are focused on advancing exploration activity that will scientifically assess our entire offshore. This can only be accomplished by utilizing state-of-the-art technology to acquire the highest quality data to form the greatest understanding of its potential,” said Jim Keating, executive vice president of Corporate Services and Offshore Development at Nalcor Energy. “The 3-D seismic survey added an additional layer of insight that has played an essential role in helping us risk reduce key prospects from a one-in-20 to a globally competitive one-in-six chance of success.”
According to a paper presented at the recent Society of Exploration Geophysicists annual meeting and authored by several people from Nalcor as well as PGS and TGS, which conducted the seismic survey, and Airbus Defence and Space, which conducted the seep survey, the new data provide evidence of potential hydrocarbon sourcing and migration. Material sized prospects have been imaged, it stated.
The 3-D survey, which covered 4,600 sq km (1,776 sq miles), used 8-km (4.9-mile) streamers, and the authors noted that this is important to properly image the potential targets. “The recent 2-D lines that uncovered the play trend demonstrated that the long-offset cable length was highly important in finding this play as the Oligocene, Eocene and Paleocene sands in this area are characterized by Class II AVO [amplitude vs. offset] responses, and the turbidites and fans are only properly imaged by looking at the full range of angle stacks out to far angles. … The shorter cable legacy data in the area did not image these features due to the limited angle range available.”
The comprehensive nature of the data gathering is paying off. The authors noted that when the Lower Tertiary trend was first identified, the nearest 2-D line was 60 km (37 miles) away. An infill program helped assess the regional extent of the play and determined that it generally follows the present-day bathymetric contour in this part of the basin. That, in turn gave some of the seep data more potential context as well.
“There were a number of satellite slicks imaged around the present-day shelf break updip from the turbidite complexes at the paleo toe of the slope,” the authors noted. “In addition, there were potential DHIs [direct hydrocarbon indicators] imaged updip along the Eocene unconformity … This could potentially be evidence of a petroleum system in the region, though much work remains to evaluate the presence and maturity of potential sources in the region.”
Early results from a 2015 seabed coring program also indicate that thermogenic hydrocarbon sources exist in the area, they added.
The 3-D survey has added insight into the sand distribution and potential charge in the Lower Tertiary units. The authors included a far-angle depth section from the fast-tracked 3-D volume that shows evidence of an Eocene turbidite fan prospect underlain by the Paleocene and a thick section of Mesozoic-age formations. Within the section is a potential chimney feature, possibly evidence of a mud volcano.
It also contains a flat spot with negative trough amplitudes higher above the spot than they are below. The authors reported that evaluation with seismic amplitude characterization and rock physics modeling is underway to separate lithology effects from fluid effects. “With the thickness and nature of units potentially in the maturity window and possible DHI evidence (chimneys, flat spots, etc.), there are early indications of potential hydrocarbon charge existing in this newly defined play trend,” the authors wrote. “To further advance our understanding of the nature and characteristics of these fan features, we have undertaken additional work on seismic inversion and spectral decomposition.” The spectral decomposition shows a sediment source channel and a deepwater fan complex.
Overall, the Nalcor authors have been quite encouraged by the information revealed in the 3-D survey. “These studies will help to further de-risk this region as exploration advances in this newly defined play trend,” they wrote.
Contact the author, Rhonda Duey, at email@example.com for more information.
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