Question

Classification of kerogen is based on the relative amount of Carbon (C), Hydrogen (H) and Oxygen (O). Which ONE of the following options is CORRECT about Type II kerogen?

• A. It is low in aliphatic compounds and H:C ratio $< 0.84$.
• B. It is rich in aliphatic compounds and H:C ratio $< 0.84$.
• C. It is low in aliphatic compounds and H:C ratio $> 1.0$.
• D. It is rich in aliphatic compounds and H:C ratio $> 1.0$.

Hint:

Remember kerogen types: \textbf{Type I:} Very high H:C (algal, oil-prone)
\textbf{Type II:} High H:C, aliphatic-rich (marine, oil-prone)
\textbf{Type III:} Low H:C, aromatic-rich (terrestrial, gas-prone)

Answer 1

The Correct Option is D

Step 1: Recall kerogen classification.
Kerogen is classified into Types I, II, and III based on elemental ratios, primarily H:C and O:C, and organic composition.
Step 2: Characteristics of Type II kerogen.
Type II kerogen is typically derived from marine planktonic material and forms under reducing conditions.
Its key features are:
-- Rich in aliphatic hydrocarbons
-- Moderately hydrogen-rich
-- Oil-prone kerogen
Elemental ratios for Type II kerogen are generally: \[ \text{H:C}>1.0 \quad \text{and moderate O:C} \] Step 3: Evaluate the given options.
(A) Low aliphatic content and low H:C ratio corresponds to Type III kerogen. Incorrect.
(B) Rich aliphatic content but low H:C ratio is inconsistent. Incorrect.
(C) Low aliphatic content with high H:C ratio is contradictory. Incorrect.
(D) Rich in aliphatic compounds with H:C ratio > 1.0$ correctly describes Type II kerogen. Correct.
Step 4: Conclusion.
The correct description of Type II kerogen is: \[ \boxed{\text{Rich in aliphatic compounds and H:C ratio }>1.0} \]