Adapted by AAPG from EarthComm and the American Geosciences Institute. Adapted with permission.
What factors affect how easily a fluid can move through sediments? How is this flow rate connected to oil production?
Many people think that oil lies in big pools below Earth’s surface. Oil actually is located in the pores within rocks (called “source rocks”). When the pores are connected, oil can flow slowly through the rock. This happens when there is a difference in fluid pressure between one place in the rock and another. The flow of fluid through sediments due to this pressure difference is called the permeability of the material.
In this investigation, you will explore the permeabilities of different materials. You will then use your observations to determine what affects permeability and how this might relate to oil production.
- 4 fluid oz each of sediments: gravel, coarse sand, fine sand and silt/clay
- 4 20 oz empty identical clear plastic bottles
- 4 oz measuring cup
- Cheesecloth and 4 rubber bands
- Water supply
- Watch with a second hand
- Safety scissors
- Paper and pen to record results
- Cut one of the plastic bottles 1/3 of the way down from the top to make a funnel. Cover the mouth of the funnel with a double layer of cheesecloth. Secure the cheesecloth with a rubber band.
- Invert the funnel into the bottom of the bottle to create a funnel/container set-up. Repeat with the other three bottles. Put 4 oz of each of the sediment types into a separate funnel.
- Have your watch ready. Pour 4 fluid oz of water into the gravel funnel and time how long it takes all the water to pass through. Record this time for the gravel.
- Repeat with the other three sediments, one at a time, recording your observations each time.
- Which sediment was the most permeable (allowed water to pass through most quickly)? Which was the least? Observe the characteristics of the different sediments. How can you explain why one was more permeable than another?
- Knowing that oil flows through the pores in and between source rocks, what qualities would petroleum geologists be looking for in source rocks that would be most productive?
- Conduct research, either in your school library or online, to find out what specific types of rocks are good source rocks and why. Share this information with other students in your class.