Phosphoria Formation is made up of Permian Shales. It is believed that the organic rich shales are the primary source to much of the oil in the region. It is thought that the oil from these shales have migrated into the Pennsylvanian Tensleep Formation, and Paleozoic reservoirs of Central and Eastern Wyoming. Due to its carbonate and chert rich depositional environment, the oil found in the Phosphoria Formation as a high sulfer content making it Type-IIS kerogen. This is important to note because sulfur rich oils have been known to mature at much lower temperatures than normal. The Tensleep Formation is the most prominent reservoir rock hosting approximately 142 million barrels of oil with about 12 fields producing from this unit. The Phosphoria Formation was sealed by the marine shale units of the Triassic Dinwoody Formation. This shale seal was broken during the Laramide Orogeny leading to the migration of oil into the Tensleep Formation. The oil now is trapped in anticlines formed by the Laramide.
