24-Pet-A1 Principles of Stratigraphy and Sedimentation · Undated paper
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 17-Pet-A1 Principles of Stratigraphy & Sedimentation, 2019-May. 3 hours duration; closed book, approved Sharp/Casio 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 6 marks each, for a Part B total of 36 marks – an 86-mark maximum (50 for Part A + 36 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, porosity); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial/deltaic/deep-marine systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, alluvial fans, deltas, deep-marine systems); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (basin analysis, well-log correlation, seismic/acoustic impedance); 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.
Definitions. Accommodation space (A) is the space available, below base level, for potential sediment accumulation, generated mainly by relative sea-level rise and/or subsidence. Sediment supply (S) is the rate at which sediment is delivered to the depositional site. Their ratio, S/A, is the fundamental control on how a stack of shallow-marine parasequences (shallowing-upward, flooding-surface-bounded packages) is arranged – the parasequence-set stacking pattern.
S/A > 1 (supply exceeds newly generated accommodation): progradational stacking – each successive parasequence's shoreline is offset basinward of the last, typical of an early-to-late highstand systems tract. S/A ≈ 1 (supply balances accommodation): aggradational stacking – successive parasequences stack essentially vertically, with little lateral shoreline movement. S/A < 1 (accommodation outpaces supply): retrogradational stacking – each successive parasequence's shoreline steps landward, characteristic of a transgressive systems tract, culminating at the maximum flooding surface where S/A is at its lowest. Note that even within a single parasequence the internal facies commonly coarsen/shallow upward (local progradation), because between two flooding events S locally and temporarily exceeds the small increment of A generated; it is the longer-term, set-scale stacking geometry that records the true regional S/A trend.
