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24-Pet-B4 Well Testing · Undated paper

Question 8 of 13: Two other thermal maturation geothermometers

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

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).

Section 3, Q3-3: Two other thermal maturation geothermometers (6 marks)

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.

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This item is printed on the source's own page 2 with the SAME label “Q3-2 (6 marks)” used immediately above for the vitrinite-reflectance question – a duplicate numbering typo in the exam itself (both parts carry equal 6-mark weight per NOTES item 5, so the typo has no scoring consequence). It is answered here as Q3-3 for clarity, and both parts are answered in full.

1. Rock-Eval Tmax – the temperature, during programmed Rock-Eval pyrolysis, at which the maximum rate of hydrocarbon generation (the S2 peak) occurs. Tmax rises with increasing thermal maturity in step with Ro (Tmax ≈ 435–445 °C near the top of the oil window, >470 °C in the overmature range). It is measured on the SAME instrument run used for HI/OI (Q2-4), so it is available “for free” alongside kerogen typing, and is especially useful where vitrinite is absent, sparse, or reworked/suppressed (e.g. Type I-dominated lacustrine rocks, which may carry too little indigenous vitrinite to date reliably).

2. Spore/pollen (palynomorph) colour – Thermal Alteration Index (TAI) – the colour of spores and pollen grains recovered from a rock progressively darkens, from pale yellow through orange/brown to black, with increasing cumulative thermal exposure, owing to progressive loss of volatile compounds and increasing aromatization of the palynomorph's organic wall. TAI is calibrated against Ro and is especially useful where vitrinite is scarce or absent (e.g. pre-land-plant, older Paleozoic marine sections), and is quick and inexpensive because it re-uses the same palynological slide preparations already made for biostratigraphic dating.

Other recognized geothermometers not detailed here include the Conodont Alteration Index (CAI, for carbonate-dominated Paleozoic sections that lack both vitrinite and palynomorphs) and biomarker isomerization ratios (e.g. sterane/hopane epimer ratios measured by GC-MS), each suited to a different lithology or data availability.