24-Pet-B4 Well Testing · December 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 2016-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, oil sands and tight-oil development, shale gas and coalbed methane, carbonate traps, siliciclastic/deltaic traps) – 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. This sitting's Section 6 is a Siliciclastic Traps section (wave-dominated delta, grain-size–permeability–porosity relations, sandstone diagenesis). The paper is entirely qualitative (draw/describe/define/list), with no numeric given data anywhere.
Reference texts: Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, migration, traps, carbonate systems, oil sands); 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, deltaic and carbonate lithofacies; sandstone diagenesis); James, N.P. & Jones, B., Origin of Carbonate Sedimentary Rocks, Wiley-Blackwell (carbonate platform/ramp/sabkha facies models); Butler, R.M., Thermal Recovery of Oil and Gas, Prentice Hall, 1991 (SAGD, CSS, oil sands thermal recovery); Green, D.W. & Willhite, G.P., Enhanced Oil Recovery, SPE Textbook Series Vol. 6 (thermal EOR mechanisms); Law, B.E. & Curtis, J.B., “Introduction to Unconventional Petroleum Systems,” AAPG Bulletin 86, 2002 (shale gas, tight gas, coalbed methane); Lee, W.J. & Wattenbarger, R.A., Gas Reservoir Engineering, SPE Textbook Vol. 5 (unconventional gas reservoir characterization).
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 fundamental distinction is whether the reservoir rock is also the source rock. A shale gas play is self-sourced and unconventional/continuous: the organic-rich mudrock itself generated the gas, which is held partly as free gas in matrix nanopores/microfractures and partly adsorbed onto organic matter (kerogen/TOC) surfaces, and the play typically has no discrete trap, seal, or hydrocarbon–water contact – gas saturation is essentially basin-wide wherever the shale is thermally mature and in the gas window. A tight gas play, by contrast, is a conventional-type sandstone or carbonate reservoir with an external (often deeper or laterally adjacent) source rock that has charged it via normal secondary migration; it usually retains a recognizable, if often subtle or basin-centred, trap geometry and can have measurable gas–water contacts locally. Both share very low matrix permeability (commonly <0.1 mD) requiring horizontal drilling and multistage hydraulic fracturing to produce economically, but shale gas additionally requires sufficient TOC and thermal maturity in the rock itself (it is judged as a source-rock play first and a reservoir second), while tight gas is judged by conventional reservoir-quality metrics (porosity, permeability, net pay) charged from elsewhere.
