CPG Petroleum Geology & Reservoir Characterization 2

Question 1

Which diagenetic process most commonly reduces reservoir porosity in deeply buried sandstones?

Accepted Answer

Quartz cementation

Answer

Quartz cementation is the dominant porosity-reducing diagenetic process in deeply buried sandstones, as silica precipitates in pore spaces at elevated temperatures.

Question 2

A reservoir has a porosity of 22% and a water saturation of 35%. What is the hydrocarbon pore volume fraction?

Accepted Answer

0.143

Answer

Hydrocarbon pore volume = porosity × (1 - Sw) = 0.22 × (1 - 0.35) = 0.22 × 0.65 = 0.143.

Question 3

In sequence stratigraphy, which systems tract is deposited during the early phase of sea-level rise following lowstand?

Accepted Answer

Transgressive systems tract (TST)

Answer

The transgressive systems tract (TST) is deposited during the early phase of sea-level rise, characterized by retrogradational stacking patterns.

Question 4

Which well log is BEST suited for identifying gas-bearing reservoirs through the 'gas effect'?

Accepted Answer

Neutron porosity log

Answer

The neutron porosity log shows anomalously low apparent porosity in gas zones due to the low hydrogen index of gas, creating the characteristic 'gas effect' crossover with density logs.

Question 5

What is the primary control on the distribution of carbonate facies in a rimmed shelf platform?

Accepted Answer

Distance from organic reef/mound margin

Answer

In rimmed shelf platforms, carbonate facies distribution is primarily controlled by the reef/mound margin, which creates a high-energy barrier separating fore-reef, reef crest, back-reef, and lagoon environments.

(CPG) Certified Petroleum Geologist Practice Test

(CPG) Certified Petroleum Geologist Practice Test

CPG Petroleum Geology & Reservoir Characterization 2