CPG CPG Geochemistry & Source Rock Analysis

Question 1

What does a Total Organic Carbon (TOC) value of 2.0 wt% or greater generally indicate about a source rock?

Accepted Answer

Good to excellent source rock potential for oil or gas generation

Answer

A TOC of 2.0 wt% or higher indicates good to excellent organic richness, meaning the rock contains sufficient organic matter to generate commercial quantities of hydrocarbons.

Question 2

Vitrinite reflectance (%Ro) is used as a thermal maturity indicator. What %Ro value marks the onset of the main oil generation window?

Accepted Answer

~0.6% Ro

Answer

The main oil generation window typically begins at approximately 0.6% Ro, where sufficient thermal energy has been applied to crack kerogen into liquid hydrocarbons.

Question 3

In Rock-Eval pyrolysis, what does the S2 peak represent?

Accepted Answer

Remaining generative potential — hydrocarbons released by thermal cracking of kerogen

Answer

The S2 peak measures the hydrocarbons generated by thermal cracking of kerogen during pyrolysis, representing the rock's remaining generative potential.

Question 4

Which kerogen type is primarily associated with marine algal organic matter and has the highest oil-generation potential?

Accepted Answer

Type II kerogen

Answer

Type II kerogen, derived largely from marine phytoplankton and algae mixed with bacterial material, has a high hydrogen index and excellent oil-generation potential.

Question 5

What is the 'Hydrogen Index' (HI) in Rock-Eval pyrolysis, and what does a declining HI with increasing maturity indicate?

Accepted Answer

HI = (S2/TOC) × 100; declining HI shows kerogen is being consumed as it generates hydrocarbons

Answer

Hydrogen Index equals (S2/TOC) × 100 and decreases with maturity because hydrogen-rich kerogen is progressively converted into expelled hydrocarbons.

(CPG) Certified Petroleum Geologist Practice Test

(CPG) Certified Petroleum Geologist Practice Test

CPG CPG Geochemistry & Source Rock Analysis