Is There Oil in Your Backyard?
The Northern Rockies region covers a wide variety of rock types, geologic structures and petroleum potential. Idaho does not have any known commercial deposits of oil and gas, while at the opposite end of the spectrum in the region is Wyoming, the leading oil producing state in the Northern Rocky Mountains.
The variability in petroleum potential is tied to the bedrock and structures that exist in the region due to events through geologic history. Idaho, for example, has very little oil because it has predominantly igneous and metamorphic rocks (such as the granite Idaho Batholith and the Snake River Plain cooled lava.) Also, the few Idaho sedimentary basins are cut by major fault systems and affected by metamorphic and thermal activity, which interfere with the development of oil and gas reservoirs. Idaho, in fact, has seen no oil and gas exploration since the early 80's. Drilling, however, has been important in discovering other natural resources, such as groundwater, geothermal energy, and mineral resources.
Wyoming, on the other hand, was explored early on for oil due to the abundance of oil seeps in the state, and has continued to be an important producer for the region. Wyoming has a number of structural anticline traps, ideal for halting the migration of oil and gas. Significant oil and gas reservoirs in Wyoming include Cretaceous-Tertiary sandstone, limestone, and shale of the Big Horn, Wind River, and Powder River Basins.
Below: Some of the sedimentary basins in the Northern Rockies region of the United States. Compare this illustration with the one at the top of this page to see which sedimentary basins have produced the most petroleum, and which ones have produced none.
A number of major sedimentary basins are found in the Northern Rockies, which have yielded varying amounts of commercial oil and gas production. The very large Williston Basin that crosses Montana, North Dakota, and South Dakota, and includes the Niobrara Chalk (an important natural gas producer). The Williston Basin had up to 10,000 feet of sediment deposited in it since the Paleozoic. Several smaller basins have also had some success in oil exploration, such as the Big Horn, Powder River (Wyoming), Denver, and Salina Basins (Nebraska, Wyoming). The organic material deposited along with basin sediments as Paleozoic seas covered parts of this region at various times through geologic history, eventually became the oil and gas reservoirs of today.
Enhanced recovery techniques, such as water flooding and horizontal drilling, will play an important role in the Northern Rockies oil and gas production. Also, large parts of this region are relatively unexplored and may possibly yield future reservoirs.
The Paleontological Research Institution