Earth Systems 3209

1. Earth Systems 3209 Reference: Chapters 21; Appendix A & B Unit: 5Earth’s Resources

2. Unit 5: Topic 3.1 Formation of Petroleum Focus on . . . • defining petroleum, crude oil, hydrocarbon, and kerogen. • describe how the origin of petroleum is dependent on the abundance of organic matter and its preservation potential.

3. Terminology associated with Petroleum • Petroleum is a naturally occurring flammable liquid that is found in geologic formations below Earth’s surface and consists of a mixture of hydrocarbons. Petroleum is also referred to as crude oil; however, both crude oil and natural gas are accepted under the term petroleum. • Crude oil is a mixture of hydrocarbons that exist in a liquid state in underground reservoirs and remain in a liquid state once subjected to atmospheric conditions.

4. Terminology associated with Petroleum • Hydrocarbons are chemical compounds that involve hydrogen and carbon atoms. Examples include: butane, propane, ethane, and methane (i.e. wet gases). • Note: that if predominantly methane exists, then it is referred to as dry gas. • Kerogen is a mixture of organic matter in sediments from which petroleum is released.

5. Origin and the Process of Formation of Petroleum 1) Organic Matter • The origin of petroleum lies in the organic matter contained in the tissues of living things. • Microscopic marine animals (zooplankton) and plants (phytoplankton) are the main sources of organic matter. • Such microscopic species are diatoms, foraminifera, radiolarian, and benthic algae. Text Reference: Page 602-603

6. Origin and the Process of Formation of Petroleum 1) Organic Matter • The abundance of organic matter is determined by: • the amount of light, • water depth, • latitude, • water temperature, • water turbidity, • the abundance of nutrients preferred by plants (e.g. phosphates and nitrates).

7. Origin and the Process of Formation of Petroleum 1) Organic Matter • The origin of petroleum lies in the organic matter contained in the tissues of living things. • Organic matter has a low preservation potential because of scavenging organisms and aerobic microbes that naturally recycle it. However, it often accumulates in quiet, low oxygen water environments which aids in its preservation. • This organic matter is stored in fine grained sedimentary and carbonate rocks. These rocks contain the primary source of organic matter from which petroleum is generated.

8. Origin and the Process of Formation of Petroleum • Organic Matter • These organic-rich rocks are called source rocks. • Upon burial, the organic matter breaks down and releases biogenic gases (primarily methane) leaving a residue enriched in hydrocarbons. • As the hydrocarbon-rich organic matter within the source rock is buried deeper and subjected to higher and higher temperatures, it is transformed into a solid waxy substance called Kerogen.

9. Origin and the Process of Formation of Petroleum 2) Preservation Potential • Preservation potential refers to the conditions that favour the preservation of organic matter. • Two most important conditions are: • Anaerobic conditions (low oxygen content) • Anaerobic conditions can exist in swamp and lagoon environments. 2) Rapid sedimentation by fine-grained material. • Examples of fine-grained material include clay/mud-size, silt-size, and sand-size particles.

10. Example 1: Under which conditions has kerogen matured enough to produce crude oil that migrates into traps? (A) deep burial, high temperature, high pressure (B) deep burial, low temperature, low pressure (C) shallow burial, high temperature, high pressure (D) shallow burial, low temperature, low pressure

11. Example 2: Which two factors are essential to the formation of petroleum? (A) decomposing material; anaerobic conditions (B) decomposing material; rapid burial by fine-grained material (C) organic matter; anaerobic conditions (D) organic matter; slow burial by coarse-grained material What is the name of the waxy organic matter, found in sedimentary rocks, which releases petroleum? Anthracite (B) Kerogen (C) Kerosene (D) Methane

12. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Questions: Which geological setting is associated with the formation of oil reserves? A) an evaporating sea in an arid climate where evaporate minerals are forming B) a tropical sea with plenty of plankton and steady deposition of fine grained sediments C) a warm swampy region with little vegetation dying which is buried rapidly D) a dry environment where desert sands are deposited and buried deeply

13. Solutions . . . Questions: Which geological setting is associated with the formation of oil reserves? A) an evaporating sea in an arid climate where evaporate minerals are forming B) a tropical sea with plenty of plankton dying and steady deposition of fine grained sediments C) a warm swampy region with little vegetation dying which is buried rapidly D) a dry environment where desert sands are deposited and buried deeply

14. Summary . . . Overview of Points covered: • Terms related to Petroleum include; • Crude oil 2) Hydrocarbon 3) Kerogen • Preservation potential depends on; • Anaerobic conditions (low oxygen content) 2) Rapid sedimentation by fine-grained material. • Origin of Petroleum involves: • Micro-organisms containing organic matter. • Accumulation of organic matter in fine sediment (source rock). • Burial and break down of organic matter. • Formation of hydrocarbons. • Changing of hydrocarbons into kerogen.