24-Pet-B4 Well Testing · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
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).
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.
The biogenic (organic) hypothesis – the mainstream, overwhelmingly evidence-supported model – holds that petroleum forms from buried, thermally matured organic matter (kerogen) in fine-grained source rocks. Its case is far stronger and more direct than the abiogenic case. (1) Biomarkers: crude oils and their source rocks contain molecular fossils – steranes (from eukaryotic sterols), hopanes (from bacterial membrane lipids), pristane/phytane (from the chlorophyll side-chain phytol) – that are structurally diagnostic of specific biological precursors and cannot form by any known inorganic reaction. (2) Optical activity: crude oils are chiral (rotate polarized light), a signature exclusively of biologically produced, enzyme-synthesised molecules; abiotic synthesis produces racemic (optically inactive) mixtures. (3) Carbon isotopes: petroleum is systematically enriched in 12C relative to inorganic carbon reservoirs (δ13C typically −25‰ to −32‰ for oil), matching the isotopic fractionation imposed by photosynthesis (Rubisco preferentially fixes 12CO2), not the heavier signature of mantle/inorganic carbon. (4) Direct source–reservoir correlation: geochemical "fingerprinting" (biomarker ratios, isotope matching) routinely ties specific oils to specific, laterally traceable, organic-rich source rock formations of known depositional age and setting, and burial-history/maturity modelling of those same source rocks (vitrinite reflectance, Tmax) independently predicts the timing and volume of expulsion consistent with the trapped charge. (5) Kerogen continuum: a complete, observable maturation sequence exists in the rock record from fresh organic matter → immature kerogen → oil-window kerogen with expelled bitumen → post-mature, gas-prone, graphitic residual kerogen, directly tying the source rock's own thermal history to the hydrocarbons found nearby.
