24-Pet-A1 Principles of Stratigraphy and Sedimentation · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 17-Pet-A1 Principles of Stratigraphy & Sedimentation, 2018-May. 3 hours duration; closed book, no calculator permitted. The paper has two parts: Part A (Questions 1–10, Sedimentology and Sedimentary Processes) – Questions 1 and 2 are mandatory (10 marks each, 20 marks), plus any five of the remaining eight (3–10) at 6 marks each (30 marks), for a Part A total of 50 marks; and Part B (Questions 11–19, Stratigraphy and Sedimentary Basin Analysis) – answer any six of the nine at 5 marks each, for a Part B total of 30 marks – an 80-mark maximum (50 for Part A + 30 for Part B).
Reference texts: Boggs, S. Jr., Principles of Sedimentology and Stratigraphy, 5th ed., Pearson (grain texture, sediment transport, bedforms, carbonate/evaporite systems, sequence stratigraphy, unconformities, stratigraphic principles); Tucker, M.E., Sedimentary Petrology, 3rd ed., Blackwell (sandstone/carbonate classification, diagenesis, dolomitization); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial/deltaic systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, deep-marine and shelf systems); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, basin classification, reservoir quality); International Commission on Stratigraphy, International Chronostratigraphic Chart (geological time scale).
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.
Modern carbonate factories are grouped by dominant biota into "photozoan" (warm-water) and "heterozoan" (cool-water) associations, which differ in nearly every respect:
| Attribute | Warm-water (photozoan) | Cool-water (heterozoan) |
|---|---|---|
| Dominant biota | Corals, calcareous green algae (e.g., Halimeda), large photosymbiotic benthic foraminifera, ooids | Bryozoans, barnacles, molluscs, red algae (rhodoliths), echinoderms, small benthic foraminifera |
| Light dependence | Photosymbiosis-dependent – restricted to the well-lit photic zone | Not light-dependent; can flourish below the photic zone |
| Temperature / latitude | Warm (generally >20°C), low latitude (<~30°) | Cool, higher latitude or areas of upwelling, regardless of latitude |
| Nutrient level | Oligotrophic (nutrient-poor) – high nutrients suppress reef-building corals | Often mesotrophic to eutrophic (nutrient-rich, e.g. upwelling zones) |
| Mineralogy | Aragonite and high-Mg calcite dominant | Low-Mg to high-Mg calcite dominant; little to no aragonite |
| Framework building | Builds rigid reefs and ooid shoals | Generally does not build wave-resistant reefs; forms unconsolidated bioclastic/rhodolith gravels and sands |
