Well of the Week - In the beginning was the Granite Wash

To a large degree, the history of the Western Canada Sedimentary Basin reflects its structural features - the West Alberta Ridge, the Meadow Lake Escarpment and the Sweetgrass Arch to name a few. But if someone says, “The Arch,” it is almost certainly the Peace River Arch they are referring to. The Arch defines the WCSB as much as any other feature.



At its highest point, the Peace River Arch rose over a kilometre from the sea floor to emerge as a significant land mass. The Arch was over 750 kilometres along its axis (O’Connell, 1994). To give a sense of scale, the Arch was as high above the ocean floor as Calgary is above sea level, and it extended further than Calgary is from Vancouver.


From its rise through its collapse at the beginning of the Carboniferous (at which time it is more properly referred to as the Peace River Embayment), the Arch has been a prolific region for oil and gas discoveries. Over the next few weeks, the Petro Ninja – Enlighten Geoscience Well of the Week will move upwards through the stratigraphic column to display examples of the productive nature of the Arch.



There have not been any oil or gas discoveries hosted in the Precambrian...yet. As a result, the first of these plays is traditionally referred to as the Granite Wash. Oil is trapped as a result of a complex interaction of repeated structural reversals and stratigraphic interfingering (Tomasz et al., 1996). While areally discrete, successful wells can be amazingly prolific. The well with the highest cumulative oil production to date (102/08-12-087-10W5/00) is projected to boast an ultimate cumulative production of 2.4 millions barrels of oil. Medium depth wells which produce without the need for horizontals or fracturing. Without a doubt these wells were very economic.



Exploration for Granite Wash oil has been out of vogue for a couple of decades due to a perception that the target portfolio has been depleted. Is it possible that a new generation of explorers applying modern techniques and tools might find a fresh set of oil pools?




References


O'Connell, S.C. (1994):Geological History of the Peace River Arch; in Geological Atlas of the Western Canada Sedimentary Basin, G.D. Mossop and I. Shetsen (comp.), Canadian Society of Petroleum Geologists and Alberta Research Council, https://ags.aer.ca/publications/chapter-28-geological-history-of-the-peace-river-arch.html, [05/07/2020].

Tomasz, D., Hein, F. and Trotter, R., 1996. Granite wash alluvial fans, fan-deltas and tidal environments, northwestern Alberta: Implications for controls on distribution of Devonian clastic wedges associated with the Peace River Arch. Bulletin of Canadian Petroleum Geology. 44. 541-565.

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