24-Pet-B4 Well Testing · Undated paper
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 17-Pet-B4 (May 2019, per its page footers). 3 hours duration; closed book. This paper's own cover page reads “17-Pet-B4, Petroleum Geology” and all five sections are descriptive/interpretive petroleum geology (terminology, source rocks, thermal maturation, stratigraphic traps, structural traps), no well-test pressure-transient content anywhere. The section marks are Section 1 = 30, Section 2 = 18, Section 3 = 22, Section 4 = 15, Section 5 = 15 (sum 100), used throughout below. The exam is entirely qualitative (explain/define/sketch).
Reference texts: Tissot, B.P. & Welte, D.H., Petroleum Formation and Occurrence, 2nd ed., Springer (kerogen typing, maceral groups, maturation stages, geothermometers); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (petroleum terminology, source rocks, traps); Boggs, S. Jr., Petrology of Sedimentary Rocks, 2nd ed., Cambridge (source-rock petrology); Allen, P.A. & Allen, J.R., Basin Analysis: Principles and Applications to Petroleum Play Assessment, 3rd ed., Wiley-Blackwell (structural trap styles); Biddle, K.T. & Wielchowsky, C.C., “Trap Types in Petroleum Basins,” AAPG Memoir 60, ch.12 (stratigraphic and structural trap classification); Mossop, G.D. & Shetsen, I. (eds.), Geological Atlas of the Western Canada Sedimentary Basin, CSPG/Alberta Research Council, 1994 (Canadian trap examples).
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.
Fold traps. (a) Compressional (fold-and-thrust belt) anticlines form by regional horizontal shortening, are often fault-cored or detached above a basal decollement, and are typical of foreland fold-thrust belts (e.g. the Canadian Rocky Mountain foothills). (b) Drape (compaction) anticlines form passively where overlying strata blanket, and differentially compact around, a pre-existing rigid basement high or a buried reef/reservoir body – no regional shortening is involved, only differential compaction of the ductile cover over a stiffer core (common over many WCSB reef trends).
Fault traps. (c) Simple normal (extensional) fault-block traps juxtapose a reservoir against an impermeable unit across a normal fault in a tilted/rotated fault block, typical of rift basins. (d) Reverse/thrust fault traps arise from compressional faulting that can REPEAT a reservoir section (a thrust sheet stacked on itself), forming a trap at the fault contact and/or in the associated hanging-wall anticline. (e) Growth (syn-depositional, listric-normal) fault / rollover anticline traps develop where continuous slip during ongoing deposition thickens the section in the downthrown hanging wall, which itself rolls over into an anticline that forms the trap – common in actively subsiding deltaic/continental-margin settings.
Salt-related traps. (f) Salt pillows (non-piercing swells) are a gentle, non-piercing upward flexure of overlying strata above a mobilizing (but not yet piercing) salt body, forming a simple drape-fold trap. (g) Salt diapirs (piercement domes) occur where salt physically pierces and intrudes through the overlying section; traps form on the diapir's FLANKS (reservoir juxtaposed against the near-vertical salt stock) and in a crestal/caprock trap directly above the residual (dissolution) caprock – a related sub-type, salt-withdrawal (rim-syncline) traps, forms in the adjacent subsiding basin as salt migrates laterally to feed the rising diapir.
