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.
A parasequence is a relatively conformable succession of genetically related beds bounded by marine flooding surfaces, typically recording one shallowing-upward cycle. A parasequence set is a succession of several parasequences stacked vertically, and the STACKING PATTERN (how each successive parasequence's shoreline position shifts relative to the last) distinguishes the two types.
In a progradational parasequence set, each successive parasequence's shoreline is offset progressively basinward (seaward) of the one below – sediment supply outpaces the creation of new accommodation space, so the shoreline advances into the basin over time. This occurs where the rate of relative sea-level RISE is low, at a highstand still-stand, or during relative sea-level FALL, and it typically dominates the upper part of a highstand systems tract and the whole of a falling-stage systems tract. In a retrogradational parasequence set, each successive parasequence's shoreline steps progressively landward, "backstepping" as accommodation is created faster than sediment can fill it – a sustained relative sea-level RISE outpacing sediment supply – and this stacking pattern defines the transgressive systems tract.
