The Permian Basin Royalty Trust is a United States oil and natural gas royalty trust based in Dallas, Texas. With a market capitalization of US $790,000,000, and an average daily trading volume of about 186,000 shares at the end of 2007, it was one of the largest royalty trusts in the United States. Its source of revenue is oil and gas pumped from the geologic formation for which it is named, the Permian Basin in west Texas, as well as a few locations in other parts of the state. Most of the Trust's properties are on the Waddell Ranch in Crane County, Texas, where it owns a 75% net overriding royalty interest in the fee mineral interests. Other properties of the trust are in 32 other Texas counties, most of which are in the western portion of the state, on the High Plains; the trust owns a 95% net overriding royalty interest in all of its properties outside of the Waddell Ranch. The principal productive zones for oil on the Waddell Ranch are in two geologic units, the Grayburg and the San Andreas, at a depth of from 2,800 to 3,400 feet below ground surface; however there are a total of 12 producing zones on the ranch, including one at a depth of 10,600 feet. Wikipedia