‘Unique’ deposits on display
Deep Channel Cores Featured In Cape Town
It is one of the largest core workshops ever offered that will focus on a single depositional environment.
“If not the largest,” clarifies Jeff Aldrich, general vice chair of the AAPG International Conference and Exhibition (ICE) in Cape Town, South Africa, and one of the organizers of its much-anticipated Africa deepwater core poster session.
This year’s ICE will be held Oct. 26-29 at the Cape Town International Convention Centre – AAPG’s first such event in South Africa.
The workshop’s size, however, isn’t the only reason for the advanced buzz.
What’s exciting, what’s potentially so rewarding for explorers about the last Monday, Tuesday and Wednesday in October, is that each of the displays to be featured combine core and logs (and most seismic as well) of confined channel flow deposit systems that have all yielded commercial hydrocarbon fields.
The cores come from four different countries – South Africa, Angola, Gabon and Nigeria – representing a range of facies and depositional styles all attributed to turbidites, specifically a complete source-to-sink-cored cross section of the “14A sequence” from the Orange Basin of South Africa and Angola blocks 15 and 17.
Aldrich, who is chief geologist at PetroSA (South Africa’s state oil company), said cores from the west African giant oil and gas fields won’t be the only ones featured. His company also has made it possible for a single third order sequence, traced for over 200 kilometers across the basin from the shelf to the deep basin plain with an integrated core, log and seismic display, to be featured.
But since this is Africa, nothing, it seems, is easy, including the organizing and planning of such a conference.
“It took some persuasion,” Aldrich said, “but this really seemed like the right idea at the right time with the current focus of industry activity on deepwater fields and the major theme of the conference on deepwater reservoirs.
“With the enthusiasm of geologists to share their experience and work in the deepwater turbidite plays it wasn’t that difficult to get participants in the core workshop,” he added.
The organizers’ first step was to find participants who could get partner approvals to display the core, as some of the samples were proprietary and had never been seen before; then, the core needed to be cut and packaged for shipping and display.
Special care was needed to ship and present the displays – a total of 454 meters of core samples will be displayed, requiring an area of 800 square meters to show it.
Organizers Answa DeLange and John Snedden say the workshop is unique because few scientists have actually seen these particular samples.
“Every delegate will get to see the displays laid out for the entire conference and meet the world’s top experts in turbidite and confined channel deposits and discuss the details while looking at the cores in person,” Snedden said.
Snedden was instrumental in securing cores from Total, Chevron and ExxonMobil.
‘A Geologic Feast’
Cores on display will include a full spectrum of these turbidite and debrite lithofacies deposited in the confined-channel complexes of African paleo-deepwater basins – from multiple operators and basins.
“The idea,” Aldrich said, “began with PetroSA wanting to use the cores available in the Bredasdorp Basin to characterize a complete basin-wide sequence and put it on display.”
It was then that Snedden heard of the idea and made inquiries to other companies to see if they would release cores to the workshop.
“The core material highlights several hierarchical scales of erosion and deposition that influence sandstone amalgamation and the preservation of intervening shale-prone units,” Snedden said, “thus impacting reservoir connectivity and oil field performance.”
The following specific areas will be featured, discussed and reviewed:
- A complete “Source-to-Sink” cored cross-section of the 14A sequence from the Orange Basin of South Africa. This sequence was featured in Frank Brown’s pioneering AAPG Studies in Geology No. 41, “Sequence Stratigraphy in Offshore South African Basins” (1995).
- Cores from Angola blocks 15 and 17, a world-class deepwater producing province with multiple billion-barrel oil fields.
- Cores covering a full spectrum of turbidite and debrite lithofacies deposited in confined-channel to distributive systems in African paleo-deepwater basins.
Snedden believes that seismic prediction of reservoir continuity and pre-drill net-to-gross estimates in African slope channel systems are greatly enhanced when calibrated with conventional core – and believes the findings will be a geologic feast and a potential bonanza.
“The main way these relate is that they are all deposited in confined channel systems, some as turbidites, some as debris flows, mass wasting; some progradational and some retrogradational.
“They are all from or related to commercial hydrocarbon fields,” he added, “so they are very practical and useful to understand both from an exploration and production viewpoint.”