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24-Pet-B4 Well Testing · December 2014

Question 17 of 18: NE–SW cross section, Western Canada Sedimentary Basin

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

EGBC National Exam — Petroleum Engineering, 2014-Dec. 3 hours duration; closed book. This sitting's own cover page reads “98-Pet-B4, Petroleum Geology” and every question is descriptive/interpretive petroleum geology (source rocks, generation, migration, traps, Canadian basin geography) – no well-test pressure-transient content anywhere. Five (5) of the paper's six 20-mark sections are marked (NOTES item 5); all six are solved in full below so this set also serves as a complete study reference. The paper is almost entirely qualitative (draw/describe/define/list), with one true numeric calculation (Q3-2, capillary seal-breach column height).

Reference texts: Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, migration, traps); Tissot, B.P. & Welte, D.H., Petroleum Formation and Occurrence, 2nd ed., Springer (kerogen typing, oil/gas windows, primary migration); Boggs, S. Jr., Petrology of Sedimentary Rocks, 2nd ed., Cambridge (source-rock lithofacies); Allen, P.A. & Allen, J.R., Basin Analysis: Principles and Applications to Petroleum Play Assessment, 3rd ed., Wiley-Blackwell (extensional basins, structural styles); Biddle, K.T. & Wielchowsky, C.C., “Trap Types in Petroleum Basins,” AAPG Memoir 60, ch.12 (stratigraphic/structural/salt trap classification); Mossop, G.D. & Shetsen, I. (eds.), Geological Atlas of the Western Canada Sedimentary Basin, CSPG/Alberta Research Council, 1994 (WCSB stratigraphy and play types).

Section 6, Q6-1: NE–SW cross section, Western Canada Sedimentary Basin (10 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Generalized NE–SW cross section, Western Canada Sedimentary Basin NE SW Shield Precambrian crystalline basement (deepening SW) Paleozoic carbonates (Devonian reef trend: Leduc, Nisku, Wabamun) Mesozoic clastics (Mannville, Cardium, Viking sands) thick foreland clastics foothills / deformed belt thrusts A B C D E ≈ 200 km (horizontal) ≈ 6 km (vertical, exaggerated)
Generalized NE–SW section across the WCSB: the wedge thins to a feather-edge on the Canadian Shield (NE) and thickens southwestward to the Rocky Mountain deformed belt/foothills. Play types (A–E): A – shallow Mannville (Athabasca) oil-sands heavy-oil play at the NE subcrop edge; B – Devonian carbonate reef (Leduc-trend) structural-stratigraphic plays; C – Cretaceous clastic stratigraphic/tight plays (Cardium, Viking); D – deep basin-centred (basin-centred gas) plays in thick foreland clastics; E – foothills structural (thrust-fold) gas plays in the deformed belt.

The WCSB is a classic asymmetric foreland basin: Precambrian Shield basement outcrops at surface in the northeast and dips gently southwest beneath a wedge of Paleozoic and Mesozoic strata that thickens dramatically toward the Rocky Mountain deformed belt, where the same section is structurally thickened again by thrust stacking. Along the section (NE→SW): (A) at the shallow NE subcrop edge, Lower Cretaceous Mannville Group (McMurray Fm) sands host the Athabasca oil sands – a biodegraded heavy-oil/bitumen play; (B) across the central basin, Devonian carbonate platform and reef buildups (Leduc, Nisku, Wabamun) form major structural-stratigraphic reef-trend plays; (C) overlying Cretaceous clastic wedges (Cardium, Viking, Mannville sands) host stratigraphic/tight oil and gas plays across the basin; (D) toward the deep foredeep, thick, low-permeability foreland clastics host basin-centred (deep basin) gas accumulations; and (E) in the Rocky Mountain foothills/deformed belt itself, thrust-faulted and folded Paleozoic–Mesozoic carbonates and clastics host structural (fold-and-thrust) gas plays.