Earth Systems 3209

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

2. Unit 5: Topic 3.4 Types of Petroleum Traps Focus on . . . • identifying and describing the types of petroleum traps. • identifying each type of petroleum trap using diagrams. • relating how density influences the relative position of petroleum in an oil trap.

3. Types of Petroleum Traps • Several geologic structures may act as petroleum traps, but all have two basic conditions in common: • Porous, permeable reservoir rock that will contain quantities of oil and gas that make it worth drilling. • Impermeable cap rock that traps oil and gas preventing it from escaping to the surface. • Types of Petroleum traps include: • Anticline Trap 3) Fault Trap • Salt Dome Trap 4) Stratigraphic Trap Text Reference: Pages 603-604

4. Well Impermeable Cap Rock Gas Oil Permeable Reservoir Rock Water Water Types of Petroleum Traps • 1) Anticline Trap: (page 604) • If a permeable rocklike sandstone or limestone is located betweenimpermeable rock layers likeshale and therocks are folded into ananticline, oil and gas can move upward in the permeablereservoir rocks, and accumulate inthe upper region of the anticline.

5. Impermeable Cap Rock Well Well Impermeable Cap Rock Permeable Reservoir Rock Gas Oil Oil Water Water Types of Petroleum Traps 2) Fault Trap (page 604) • If faulting can shift permeable and impermeablerocks so that the permeablerocks always have impermeablerocks above them, then an oiltrap can form. • Note that bothnormal faults and reverse faultscan form this type of oil trap.

6. Types of Petroleum Traps • Salt Dome Trap (page 604) • Here we see salt that has moved up through the Earth, punching through and bending rock along the way. • Oil can come to rest right up against the impermeable salt, which makes salt an effective trap rock.

7. Types of Petroleum Traps • Limestone Reef Trap (page 604) • Limestone reef trap is a type of stratigraphic trap. • When coral reefs become buried by other impermeable sediments they can form excellent oil sources and reservoirs. Impermeable Cap Rock Permeable Reservoir Rock

8. Types of Petroleum Traps • Density is the physical property that distributes petroleum in a reservoir. • Water is denser than oil and oil is denser than gas. • Therefore, when drilling into a petroleum trap, gas is encountered first, followed by oil and then water. • Some reservoirs may have all three components, whereas some reservoirs may only have two components or one component.

9. Example 1: • Which petroleum trap would be formed by a simple fold? • (A) anticline (B) fault • (C) salt dome (D) stratigraphic • The limestone reef trap belongs to which type of petroleum trap? • (A) anticline (B) fault • (C) saltdome (D) stratigraphic

10. Example 2: Based on the diagram below, which is the correct match between the force and petroleum trap produced? Oil

11. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Questions: • Which sequence is correct from highest density to lowest density? • (A) gas → oil → water • (B) oil → gas → water • (C) oil → water → gas • (D) water → oil → gas

12. Solutions . . . Questions: • Which sequence is correct from highest density to lowest density? • (A) gas → oil → water • (B) oil → gas → water • (C) oil → water → gas • (D) water → oil → gas

13. Summary . . . Overview of Points covered: • Types of Petroleum traps include: • Anticline Trap • Fault Trap • Salt Dome Trap • Stratigraphic Trap