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.
(1) In-situ stress contrast between layers. A hydraulic fracture propagates perpendicular to the minimum horizontal stress and tends to stay confined within the layer of lowest stress; a bounding layer (shale barrier, evaporite) with substantially higher minimum horizontal stress than the target zone acts as a stress barrier that resists height growth out of zone, since more net pressure is needed to extend the fracture into the higher-stress rock.
(2) Rock mechanical property contrast (Young's modulus / ductility). A softer, more ductile bounding shale absorbs fracture-tip energy through plastic deformation rather than propagating a sharp brittle fracture, and ductile layers tend to “heal” or blunt a fracture tip — a stiffer, more brittle target formation propagates a fracture efficiently while an adjacent ductile layer resists further extension into it.
(3) Fluid leak-off into permeable/natural-fracture zones. Where the fracture face encounters a naturally permeable streak or an open natural fracture network, treatment fluid leaks off into the formation faster than it can build the net pressure needed to extend the fracture tip further, which starves the fracture of the fluid volume required for continued propagation and can arrest growth at that interface.
