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These 10 free PEC questions are organized by exam domain, so you can see how each part of the Petroleum Engineering Certification blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: Reservoir Engineering
Question 1
A gas-condensate reservoir has an average pressure of 4,800 psia and a dewpoint of 4,200 psia at reservoir temperature. After a well is opened to a larger choke, its flowing bottomhole pressure falls to 3,600 psia. Gas deliverability is below the single-phase prediction, although tubing condition is unchanged. Which phase-behavior effect can explain the shortfall while average reservoir pressure remains above the dewpoint?
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Correct answer: C - Condensate accumulates near the well and reduces gas relative permeability.
Question 2
Early water breakthrough has left substantial unswept oil in a nearly homogeneous sandstone waterflood. Tracer and production-log studies show no discrete fracture or thief zone. Displacement tests identify an unfavorable water-to-oil mobility ratio, while recovery within the swept rock is satisfactory. Chemical compatibility and injectivity have been demonstrated. The team wants better sweep rather than a treatment aimed primarily at residual oil in already swept pores. Which pilot directly addresses that objective?
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Correct answer: B - Add polymer to injection water to reduce mobility and improve sweep.
Question 3
The diagnostic record from a constant-rate drawdown test of a vertical well in a single-phase reservoir shows:
0.01-0.1 hour: pressure change and its logarithmic-time derivative coincide along a unit-slope trend.
0.5-5 hours: the derivative is horizontal.
After 12 hours: the derivative turns upward.
For an infinite-acting radial-flow estimate of permeability-thickness, which interval belongs in the analysis?
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Correct answer: B - Use 0.5-5 hours, because the horizontal derivative identifies the radial-flow interval.
Domain 2: Drilling Engineering
Question 4
A deviated section is being planned with 12.0-ppg mud at 10,000 ft true vertical depth and 13,500 ft measured depth. The approved operating limits require at least 11.8 ppg static mud density, no more than 13.0 ppg bottomhole equivalent circulating density (ECD), and at least 425 gal/min for hole cleaning. The hydraulic model predicts annular friction losses of 624 psi at 550 gal/min and 416 psi at 450 gal/min. Total standpipe pressure at 550 gal/min is 3,000 psi; surface annular backpressure is zero. Select the assessment that satisfies both pressure control and hole cleaning.
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Correct answer: A - ECD is 13.2 ppg at 550 gal/min; use the validated 450-gal/min condition.
Question 5
The drillstring becomes immobile after remaining stationary across a permeable, depleted sandstone during a survey. Mud hydrostatic pressure substantially exceeds formation pressure. The crew can still circulate at the previous rate with unchanged standpipe pressure and full returns, but cannot rotate or reciprocate the string. There was no upward pipe movement when sticking began. What mechanism best fits this combination?
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Correct answer: A - Differential-pressure sticking against the filter cake.
Domain 3: Formation Evaluation
Question 6
A clean, quartz-rich sandstone is logged in a near-gauge borehole. Environmental corrections are small, and the density and neutron curves use the same sandstone porosity scale. Deep resistivity is much higher than in nearby brine-filled sandstone. Apparent density porosity is 0.27, whereas neutron porosity is 0.13. The combined response is most consistent with:
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Correct answer: D - Gas occupying part of the sandstone's pore space.
Question 7
Core-calibrated petrophysical data for a clean sandstone interval are:
Effective porosity: 0.25
True formation resistivity: 10 ohm-m
Formation-water resistivity at reservoir temperature: 0.10 ohm-m
Archie parameters: a = 1 and m = n = 2
All other reservoir-quality screens pass. The interval passes the water-saturation screen only when Sw is no greater than 0.50. Using Archie's relationship, which saturation and screening conclusion follow?
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Correct answer: D - Sw = 0.40; the interval passes the saturation screen.
Domain 4: Production Engineering
Question 8
Immediately after a producing well is routed into a higher-pressure gathering header, its stabilized liquid rate falls. Reservoir pressure, completion condition, tubing geometry, and fluid properties are unchanged. For this operating range, the liquid can be treated as single phase and incompressible, and the nodal model has one stable operating point. With flowing bottomhole pressure on the vertical axis and rate on the horizontal axis, how should the change appear in a sandface nodal analysis?
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Correct answer: B - The outflow curve moves upward, while the inflow curve remains unchanged.
Domain 5: Facilities
Question 9
Export demand falls at a gas-compression station, and the centrifugal compressor's anti-surge recycle valve opens. Flow through the compressor remains above the anti-surge control line; pressure, temperature, and vibration are within approved limits. The unit is still needed to supply the reduced demand. An operator proposes closing the recycle valve to avoid recompressing gas. Which response preserves stable operation?
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Correct answer: C - Keep anti-surge control active, allowing recycle to maintain sufficient flow through the compressor.
Domain 6: Petroleum Economics
Question 10
An optional workover requires $500,000 today and would generate incremental net operating cash inflows of $350,000 at the end of each of the next two years. It also adds $80,000 of abandonment expenditure at the end of year 2, beyond the abandonment cost already required without the workover. A nonrefundable $100,000 diagnostic study has already been paid. These are the only cash-flow differences, and tax effects are already included. At a 10% annual discount rate, what is the approximate incremental net present value of proceeding today, and what decision does the NPV criterion support?
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Correct answer: D - +$41,300; proceed with the workover.
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