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 commercial petroleum accumulation requires five elements to all be present and to occur in the correct relative timing; the absence of any one, or the wrong timing, gives a dry hole even where the others are excellent.
(1) Source rock. An organic-rich (typically >1–2 wt% TOC), fine-grained rock that has been buried to sufficient depth/temperature to thermally mature its kerogen and generate oil and/or gas. (2) Migration pathway. A permeable carrier bed, fracture network or fault system connecting the mature source rock to a reservoir, allowing expelled hydrocarbons to move updip (primary migration out of the source, secondary migration through carrier beds) toward a trap. (3) Reservoir rock. A rock with sufficient porosity to store hydrocarbons and permeability to allow them to flow to a wellbore at economic rates (typically a sandstone or a porous/fractured carbonate). (4) Trap. A structural (e.g. anticline, fault) or stratigraphic (e.g. pinchout, unconformity) closure that halts further updip migration and concentrates hydrocarbons in the reservoir. (5) Seal (cap rock) and correct timing. An impermeable rock (shale, evaporite, tight carbonate) directly overlying the reservoir at the trap, capable of holding a capillary entry pressure greater than the buoyancy pressure of the trapped column – and critically, the trap and seal must already exist before or during the migration event, since hydrocarbons that arrive at an as-yet-unformed trap simply migrate on and are lost.
