24-Pet-B3 Petroleum Geology · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams, May 2016 — 98-Pet-B3, Oil and Gas Evaluation and Economics (3 hours, closed book, approved non-programmable calculator only). The exam's own cover page is titled "Oil and Gas Evaluation and Economics" and every question is property valuation / reserves & production economics / DCF-NPV screening content — no geology anywhere.
Reference texts: Thompson & Wright, Oil Property Evaluation; Canadian Oil and Gas Evaluation Handbook (COGEH), Vol. 1 (Society of Petroleum Evaluation Engineers, Calgary Chapter); National Instrument 51-101, Standards of Disclosure for Oil and Gas Activities (Canadian Securities Administrators); SPE/WPC/AAPG/SPEE Petroleum Resources Management System (PRMS); Economides & Nolte, Reservoir Stimulation; Ahmed, Reservoir Engineering Handbook.
The exam's own instructions ask for only 7 of the 10 short-answer questions and note the Cash-Flow/Future-Value tables are graded by column; for "choose N of M" exams, every item below is answered in full as a study resource. Questions 1–10 correspond to the exam's printed Short-Answer items 1–10; Questions 11–20 correspond to the printed Multiple-Choice items 1–10; Question 21 is the Future Value table; Question 22 is the Cash Flow table.
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.
Four unconventional gas resource types now under active development, beyond a conventional free-gas reservoir, are:
(1) Shale gas — natural gas held within the pore space and adsorbed onto the organic matter of a very-low-permeability, organic-rich shale (e.g., the Montney or Duvernay in Western Canada). Matrix permeability is typically in the nanodarcy range, so economic production needs a horizontal well with multistage hydraulic fracturing to create enough fracture surface area for gas to reach the wellbore.
(2) Tight gas — gas trapped in a conventional lithology (sandstone or carbonate) whose matrix permeability has been reduced by diagenesis to well under 0.1 mD; it also needs hydraulic fracturing (often without needing a horizontal well) to flow at commercial rates.
(3) Coalbed methane (CBM) / coal-seam gas — methane adsorbed onto the internal surface area of coal rather than existing as free gas; production requires dewatering the coal seam to lower reservoir pressure so the gas desorbs (Langmuir isotherm) and flows to the well, which is why CBM wells typically produce water first and gas rate builds over months.
(4) Gas hydrates — methane trapped in an ice-like clathrate lattice, stable at low temperature and moderate pressure in Arctic permafrost and deep-water marine sediments. In-place volumes are enormous, but no fully commercial production method has been demonstrated; depressurization and thermal stimulation are the leading pilot-scale techniques.
