Wyoming is a state rich in hydrocarbon resources, due to a fortuitous overlap of geology and geography. The bulk of the oil and gas in Wyoming began as organic-rich shales deposited in the shallow Permian seas of the Phosphoria Formation (~278–253 million years ago) or the Cretaceous western interior seaway (~124–65 million years ago). Subsequent burial and increased pressures and temperatures allowed the organic material to mature into hydrocarbons, which migrated in the subsurface through fractures and porous sandstones and were ultimately trapped in various locations in the basins throughout the state. These traps are currently Wyoming’s oil and gas fields.
Wyoming also has enormous deposits of oil shale rock, known as marlstone, which can be converted into crude oil through a process called destructive distillation. The Green River Formation, found in parts of Wyoming, Colorado, and Utah, contains the largest known oil shale deposits in the world. Wyoming’s oil shale deposits, concentrated in the Green River and Washakie basins in the southwestern part of the state, contain an estimated 300 billion barrels of oil, equal to about one-fourth of the world’s proven oil reserves.
What is Oil?
Crude or “unprocessed” oil is a fossil fuel, meaning that it formed naturally from decaying plants and animals living in ancient seas millions of years ago. Wyoming was once an ancient sea.
Salt Creek Oil Field, Natrona County, Wyoming.
Crude oil contains hydrocarbons, which are molecules that contain hydrogen and carbon. Hydrocarbons contain a lot of energy, which is why oil is so useful as an energy resource. These hydrocarbons formed from billions of tiny plants and animals that once inhabited the Earth’s ancient seas. When they die and sink, their bodies add carbon to the sea floor sediments. When underground carbon-rich sediments are heated for about 10 million years, the carbon compounds change into hydrocarbons, or oil. Because oil is lighter than water it can float up through cracks and pores in the rocks. When rocks without pores or cracks stop the oil from rising any higher, a pocket of oil is formed, which can be accessed using high-tech machinery for horizontal and vertical drilling.
Geologists gather information to predict where oil is located underground. Data from nearby wells, regional geology, geophysical tools, satellite imagery, and surface oil seeps help them predict where a successful drill site might be located. While some test wells lead to the successful discovery of oil others find what are called “dry holes.” On occasion, drilling a test well will find no oil in the predicted zone, but finds it in other layers of rocks.
What is Natural Gas?
Natural gas is a vital component of the world’s supply of energy. This flammable gas consists largely of methane and other hydrocarbons, occurs naturally underground and is primarily used as a fuel source. Natural gas is one of the cleanest and safest energy fuels.