CPG Risk Assessment & Mitigation 3 — Questions and Answers
Question 1: In petroleum exploration portfolio management, what does 'portfolio diversification' primarily aim to reduce?
- The total capital expenditure across all prospects
- The variance in exploration outcomes caused by correlated geological risk (Correct answer)
- The number of dry holes drilled in a single fiscal year
- The geographic concentration of assets in politically stable regions
Correct answer: The variance in exploration outcomes caused by correlated geological risk
Portfolio diversification reduces outcome variance by including prospects with uncorrelated risk factors, so failures in one risk segment do not doom the entire portfolio.
Question 2: A well encounters a structural trap but finds the reservoir water-saturated. Which risk factor was not adequately mitigated?
- Trap geometry and closure
- Reservoir quality and porosity
- Seal integrity above the reservoir
- Charge risk and hydrocarbon migration (Correct answer)
Correct answer: Charge risk and hydrocarbon migration
A water-saturated reservoir in an otherwise valid trap indicates that hydrocarbons never migrated into the structure, pointing to a charge risk failure.
Question 3: What is the main advantage of using 'P10-P50-P90' probabilistic ranges in resource estimation?
- They provide a single deterministic volume for economic modeling
- They communicate uncertainty by expressing the full range of possible outcomes (Correct answer)
- They eliminate the need for Monte Carlo simulation
- They define the minimum commercial field size for investment approval
Correct answer: They communicate uncertainty by expressing the full range of possible outcomes
P10-P50-P90 ranges convey geological uncertainty by showing low-case, mid-case, and high-case resource estimates rather than a false single number.
Question 4: Which factor would most increase the seal risk for an exploration prospect?
- High net-to-gross ratio in the reservoir interval
- Presence of natural fractures cutting through the caprock (Correct answer)
- Low geothermal gradient in the basin
- Thick Paleozoic source rock underlying the trap
Correct answer: Presence of natural fractures cutting through the caprock
Natural fractures cutting through the caprock create pathways for hydrocarbon leakage, significantly increasing seal breach risk.
Question 5: What does 'expected monetary value' (EMV) represent in exploration risk assessment?
- The net present value of a discovered field at peak production
- The probability-weighted average of all possible financial outcomes (Correct answer)
- The maximum capital exposure if a well is a dry hole
- The minimum acceptable return on investment for project approval
Correct answer: The probability-weighted average of all possible financial outcomes
EMV is calculated by weighting each possible outcome (success or failure) by its probability, giving a risk-adjusted expected financial return.
Question 6: In the context of trap risk, what does 'spill point' control refer to?
- The depth at which oil spills from drilling equipment
- The structural low point of a closure that limits maximum hydrocarbon column height (Correct answer)
- The pressure at which a seal fails and hydrocarbons escape
- The point in time when production exceeds pipeline capacity
Correct answer: The structural low point of a closure that limits maximum hydrocarbon column height
The spill point is the lowest structural closure of a trap; hydrocarbons accumulate only up to this level, controlling the maximum possible column height.
Question 7: Which geochemical indicator is most useful for assessing charge risk in a frontier basin with limited well control?
- Vitrinite reflectance (Ro) of source rock samples (Correct answer)
- Resistivity log response in the reservoir interval
- Acoustic impedance contrast from seismic inversion
- Formation water salinity from mud log analysis
Correct answer: Vitrinite reflectance (Ro) of source rock samples
Vitrinite reflectance (Ro) measures thermal maturity of source rocks, indicating whether they have reached the oil or gas generation window and therefore charge potential.
CPG Risk Assessment & Mitigation 3
In petroleum exploration portfolio management, what does 'portfolio diversification' primarily aim to reduce?