Which kerogen type is composed of napthenes, aromatics and aliphatics, commonly found in rocks deposited in marginal marine carbonates and shales, and is volumetrically the most important source rock for oil?

Which kerogen type is composed of napthenes, aromatics and aliphatics, commonly found in rocks deposited in marginal marine carbonates and shales, and is volumetrically the most important source rock for oil?

• A. Type I Kerogen
• B. Type II Kerogen
• C. Type III Kerogen
• D. Type IV Kerogen

Answer: (B)

Focus in on how kerogen types relate to hydrocarbon generation and depositional environment. Napthenes (cycloalkanes), aromatics, and aliphatics together point to marine-derived organic matter that is oil-prone. This combination is characteristic of Type II kerogen, which forms in marine settings such as marginal marine carbonates and shales and has high potential to generate liquid hydrocarbons. Because Type II kerogen is widespread in these settings and is oil-prone, it is the volumetrically most important source rock for oil. In contrast, Type I kerogen is derived mainly from lacustrine (freshwater) algae and is very oil-prone but less abundant globally; Type III kerogen comes from terrestrial plants and is gas-prone; Type IV is largely inert and yields little hydrocarbons.

Focus in on how kerogen types relate to hydrocarbon generation and depositional environment. Napthenes (cycloalkanes), aromatics, and aliphatics together point to marine-derived organic matter that is oil-prone. This combination is characteristic of Type II kerogen, which forms in marine settings such as marginal marine carbonates and shales and has high potential to generate liquid hydrocarbons. Because Type II kerogen is widespread in these settings and is oil-prone, it is the volumetrically most important source rock for oil. In contrast, Type I kerogen is derived mainly from lacustrine (freshwater) algae and is very oil-prone but less abundant globally; Type III kerogen comes from terrestrial plants and is gas-prone; Type IV is largely inert and yields little hydrocarbons.