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.
Oil sands are considered unconventional because the hydrocarbon they host – bitumen – is so heavily biodegraded and viscous (in-situ viscosities on the order of 105–106+ cP, versus <10 cP for a typical conventional light oil) that it is essentially immobile in the reservoir at native temperature and pressure and cannot be produced by conventional pressure-depletion drive: even with a perfectly permeable, well-sorted host sand (e.g. the McMurray Formation), the bitumen simply will not flow to a wellbore under an ordinary pressure differential. Production instead requires either physically removing the rock (surface mining, economic only where the deposit is shallow, roughly <75 m, and the overburden-to-pay-thickness strip ratio is favourable) or reducing the bitumen's viscosity in place by adding heat (in-situ thermal recovery, e.g. steam-assisted gravity drainage (SAGD) or cyclic steam stimulation (CSS), which inject steam to raise reservoir temperature, drop bitumen viscosity by several orders of magnitude, and allow gravity- or pressure-driven drainage to a producing well). Both are fundamentally different technology sets from the pressure-depletion or waterflood methods used on conventional oil, which is the defining reason oil sands are classed as unconventional rather than simply as heavy conventional oil.
