24-Pet-B4 Well Testing · December 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 2016-Dec. 3 hours duration; closed book. This sitting's own cover page reads “98-Pet-B4, Petroleum Geology” and every question is descriptive/interpretive petroleum geology (source rocks, hydrocarbon chemistry, oil sands and tight-oil development, shale gas and coalbed methane, carbonate traps, siliciclastic/deltaic traps) – no well-test pressure-transient content anywhere. Five (5) of the paper's six 20-mark sections are marked (NOTES item 5); all six are solved in full below so this set also serves as a complete study reference. This sitting's Section 6 is a Siliciclastic Traps section (wave-dominated delta, grain-size–permeability–porosity relations, sandstone diagenesis). The paper is entirely qualitative (draw/describe/define/list), with no numeric given data anywhere.
Reference texts: Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, migration, traps, carbonate systems, oil sands); Tissot, B.P. & Welte, D.H., Petroleum Formation and Occurrence, 2nd ed., Springer (kerogen typing, maceral groups, catagenesis); Boggs, S. Jr., Petrology of Sedimentary Rocks, 2nd ed., Cambridge (source-rock, deltaic and carbonate lithofacies; sandstone diagenesis); James, N.P. & Jones, B., Origin of Carbonate Sedimentary Rocks, Wiley-Blackwell (carbonate platform/ramp/sabkha facies models); Butler, R.M., Thermal Recovery of Oil and Gas, Prentice Hall, 1991 (SAGD, CSS, oil sands thermal recovery); Green, D.W. & Willhite, G.P., Enhanced Oil Recovery, SPE Textbook Series Vol. 6 (thermal EOR mechanisms); Law, B.E. & Curtis, J.B., “Introduction to Unconventional Petroleum Systems,” AAPG Bulletin 86, 2002 (shale gas, tight gas, coalbed methane); Lee, W.J. & Wattenbarger, R.A., Gas Reservoir Engineering, SPE Textbook Vol. 5 (unconventional gas reservoir characterization).
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.
The standard, near-universal method is a long horizontal wellbore landed within the target tight-oil interval, completed with multistage (plug-and-perf or sliding-sleeve) hydraulic fracturing along its length, typically at 20–60 stage intervals, and produced with artificial lift once natural drive weakens. Horizontal drilling maximizes reservoir contact along a single wellbore through a laterally continuous but vertically thin, very-low-permeability interval (matrix permeability commonly <0.1 mD, sometimes <0.01 mD), which a vertical well could never intersect enough rock volume to produce economically. Multistage hydraulic fracturing then creates a dense network of induced fractures perpendicular to the wellbore, each fracture stage draining its own local stimulated-rock-volume (SRV); because matrix permeability is far too low to flow oil more than a few tens of metres to a fracture on an economic timescale, closer fracture spacing (shorter frac stages) directly increases both initial rate and ultimate recovery, up to the point where stages begin to interfere with one another. Reservoir characterization (natural fracture orientation, in-situ stress direction, brittleness/mineralogy from logs and core) is used up front to orient the horizontal well along the minimum-stress direction, so that induced fractures propagate perpendicular to the wellbore and intersect the maximum matrix volume.
