Green River Basin

Ultra Petroleum has the largest acreage position in the Pinedale Field, which is rated one of the top five natural gas fields in the United States.

Ultra Petroleum controls more than 84,000 gross (49,000 net) acres of leases in and around the prolific Jonah and Pinedale natural gas fields of the Greater Green River Basin in southwest Wyoming. In 2009, both the Pinedale and Jonah Fields were among the top ten U.S. natural gas plays based on proved reserves. Ultra Petroleum operates over 60 percent of this acreage position and currently has an interest in over 1,850 producing wells in the field.

As of year-end 2012, Ultra had a remaining inventory of over 5,000 gross (2,900 net) future wells equating to proved, probable and possible (3P) reserves of 9.6 Tcfe. There is still over 75 percent of the field yet to be developed. Ultra's third-party reservoir engineering firm, Netherland, Sewell & Associates, Inc. (NSAI), has identified and engineered the future net drilling locations with average per location reserves of over 4.0 Bcfe.

The Bureau of Land Management (BLM) issued the Pinedale Record of Decision (ROD) in September 2008. Under the ROD, Ultra Petroleum gains year-round access to the Pinedale Field for drilling and completion activities in development areas. This additional access has lead to increased drilling efficiencies and allowed for accelerated development of the field.