24-Pet-B4 Well Testing · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 2015-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, hydrocarbon chemistry, migration/unconventional reservoirs, carbonate traps, structural 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, carbonate systems); Tissot, B.P. & Welte, D.H., Petroleum Formation and Occurrence, 2nd ed., Springer (kerogen typing, maceral groups, catagenesis); Boggs, S. Jr., Petrology of Sedimentary Rocks, 2nd ed., Cambridge (source-rock and carbonate lithofacies); Allen, P.A. & Allen, J.R., Basin Analysis: Principles and Applications to Petroleum Play Assessment, 3rd ed., Wiley-Blackwell (structural styles, unconventional systems); Biddle, K.T. & Wielchowsky, C.C., “Trap Types in Petroleum Basins,” AAPG Memoir 60, ch.12 (structural trap classification); James, N.P. & Jones, B., Origin of Carbonate Sedimentary Rocks, Wiley-Blackwell (carbonate platform/ramp/sabkha facies models); Law, B.E. & Curtis, J.B., “Introduction to unconventional petroleum systems,” AAPG Bulletin 86 (basin-centred gas); Mossop, G.D. & Shetsen, I. (eds.), Geological Atlas of the Western Canada Sedimentary Basin, CSPG/Alberta Research Council, 1994 (WCSB stratigraphy and Canadian basin geography).
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.
A detached (isolated) carbonate bank is not attached to any landmass and is surrounded entirely by open marine water, so its geomorphic zonation is controlled purely by wind/wave-energy orientation rather than by a shoreline. The windward margin, facing the dominant wind and wave approach, is the highest-energy zone and hosts reef and ooid/skeletal grainstone shoals; the bank-top interior (lagoon) is sheltered and low-energy, accumulating carbonate mud and peloidal/muddy sediment; the leeward margin, facing the subordinate wind, is lower energy than the windward side but still elevated relative to the lagoon, typically hosting scattered patch reefs; and the bank's flanks drop off into slope/basin deposits (fine, often periplatform, carbonate mud and debris shed from the bank top).
Reservoir potential (assuming no diagenesis, i.e. judging purely on primary depositional texture): the windward reef/shoal grainstone has the best reservoir potential – high-energy winnowing removes fine carbonate mud, leaving well-sorted, well-rounded, high-primary-porosity grainstone with good interconnected pore throats. The leeward patch-reef margin has moderate potential – framework and grain-supported facies with reasonable porosity, but generally more heterogeneous and mud-richer than the windward shoal. The bank-top lagoon has poor potential – low-energy carbonate mud (lime mudstone/wackestone) has high total porosity but very fine pore throats and low permeability, so it behaves poorly as a reservoir even before any diagenetic occlusion. The slope/basin facies likewise has poor reservoir potential (fine-grained, low permeability), though it can be an effective source rock or seal instead.
