24-Pet-A1 Principles of Stratigraphy and Sedimentation · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 98-Pet-A1 Principles of Stratigraphy & Sedimentation, 2014-Dec. 3 hours duration; closed book, no calculator permitted. The paper has three parts: Part A1 (Questions 1–7, sedimentary processes, 5 marks each, answer any 4 of 7 for 20 marks), Part A2 (Questions 8–15, brief/multiple-choice, 3 marks each, answer any 5 of 8 for 15 marks), and Part B (Questions 16–24, stratigraphy, 5 marks each, answer any 6 of 9 for 30 marks) – a 65-mark maximum.
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 (carbonate classification, diagenesis, dolomitization); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, trace fossils); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, 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.
Conformable units can stack in three fundamental patterns, defined by the same accommodation-versus-sediment-supply balance introduced in Question 21, but here generalized beyond the shoreline-specific parasequence case to any conformable stacking of facies belts: progradational (facies belts shift basinward through time – supply > accommodation, e.g. Question 21's progradational parasequences); retrogradational (facies belts shift landward through time – accommodation > supply, e.g. Question 21's retrogradational parasequences); and aggradational (successive units stack essentially vertically, with no significant lateral shift of facies belts – supply ≈ accommodation, so the depositional profile simply builds upward in place without net advance or retreat). A fourth, degenerate case – degradational (retreating without deposition) – occurs where accommodation loss/erosion dominates so strongly that no net conformable unit accumulates at all, technically producing an unconformity (Question 16) rather than a further conformable stack.
