Oil and Gas Facts

What is petroleum?

Petroleum is composed of hydrocarbon molecules, the smallest of which is methane (also known as natural gas; CH4).  Larger and more complex hydrocarbon compounds are formed when additional carbon and hydrogen atoms are bonded together; ethane (C2H6) and propane (C3H8) are just two examples. 

How is petroleum formed?

Petroleum is formed when organic matter is buried and subjected to elevated pressures and temperatures for several million years.  To generate oil, pressures on the order of 3,000 pounds per square inch (psi) are required, along with temperatures ranging from 140 to 230 degrees Fahrenheit (°F).  To generate natural gas, slightly higher temperatures (212 to 392°F) are needed.

A multi-purpose material

Petroleum hydrocarbons are found in many products we use on a daily basis.  For example, oil and gas are used as fuels to heat and light our homes, and oil is a common lubricant for engines and mechanical equipment.  Petroleum hydrocarbons are also found in plastics, vinyl, paint, and acrylic fabrics.  Even some personal care items, like deodorant and perfume, are derived from petroleum hydrocarbons!

Where is petroleum found?

In conventional petroleum systems, oil and gas migrate from the source rocks in which they were generated to reservoir rocks that have pore spaces or fractures sufficient to store the petroleum hydrocarbons.  The best reservoir rocks are those that have high permeability, which measures the degree and nature of connectivity between pore spaces and/or fractures.  Oil and gas continue to migrate until they come into contact with low-permeability rocks that prevent the further flow of oil and gas.  These rocks are known as cap rocks since they “cap off” or seal petroleum inside the reservoir, creating a “trap”.  Two kinds ofDrake-Well

reservoir traps are common in Pennsylvania: stratigraphic and structural.  Stratigraphic traps occur where the physical characteristics and layering of rock units trap permeable reservoir rocks in between less permeable rocks.  Structural traps are created when rocks that have been deformed by folding or faulting prevent the migration of petroleum hydrocarbons.  Here in Pennsylvania, a majority of the oil and gas production to date is derived from conventional sandstone reservoirs, which are relatively shallow and are associated with stratigraphic traps in the Appalachian Plateaus province of western PA and deeper and more structural complex in the Ridge and Valley Province of central PA.


What is the Pennsylvania-petroleum link?

 Pennsylvania is the birthplace of commercial oil production, thanks to Colonel Edwin L. Drake (see photo above).  Specifically looking for oil, Drake drilled the first commercially productive oil well in Titusville, PA in 1859, launching a global industry upon which most of our modern lives depend. Some of the world's largest corporations are concerned with various aspects of the oil and gas industry: exploration, production, refining, marketing, and research of petroleum. For more detailed information, see Oil and Gas in Pennsylvania (1.87 MB) or Pennsylvania Geology, vol. 29, no. 1 (931 KB).