The Upper Green River Basin In Wyoming

Introduction

The Pinedale Field in the Greater Green River Basin of southwest Wyoming is the second largest gas field in the United States and along with Jonah Field, a significant new natural gas resource in America. Estimates of recoverable gas from the Pinedale Field exceed 27 TCF. Ultra Petroleum, Inc. has the largest operating position in the Field. Primary production is from over-pressured, tight-gas sandstones of the Upper Cretaceous Lance Formation and upper part of the undifferentiated Mesaverde (“Lance Pool”), coincident with the Pinedale Anticline. Current development along the Pinedale Anticline spans an area over 3 miles in width and 30 miles in length(Lewan: 3691-3723). The gross hydrocarbon-bearing column, which exceeds 5,000 feet in total thickness, consists mainly of fluvial and flood plain facies rocks deposited in a broad alluvial valley. In order to better understand the Lance Pool reservoir characteristics and to optimize the development of the Pinedale Field, Ultra Petroleum Corp embarked on a coring program in which 10 wells were cored and a total of 852 feet of Lance Pool rock was recovered. Detailed analysis of the core integrated with Ultra's geological, petrophysical and geophysical models has led to a unique understanding of the Lance Pool. The alluvial sandstones of the Lance Pool were deposited in a rapidly subsiding basin by modest-sized rivers reflecting constant channel-belt migration. The resulting reservoirs are laterally- and vertically discontinuous, multi-story sandstones. Effective reservoir characteristics include lower porosities and permeability, a greater range of effective water saturations and a thicker net pay section than previously believed. Multiple fracs are required in order to effectively produce the Lance Pool Reservoir (Keefer: 305-311)

Field Development Plans or Trends

Over the past 10 years the Jonah Field and the Pinedale Anticline located in the Upper Green River Basin (UGRB) of southwestern Wyoming has seen a dramatic increase in the number of wells being drilled. Due to the technological advancements made by the oil & gas industry in drilling and completing these large volume gas/condensate wells, there has been a rapid development of the producing fields(Doherty: 45-61). Since 2004, the Wyoming Department of Environmental Quality (WDEQ), Air Quality Division (AQD) has been collecting inventories from all oil & gas operations located in the Jonah and Pinedale fields within Sublette County, Wyoming. There were 1,811 wells in the Jonah Field in 2008, an increase of 1,272 wells since 2004, while there were 1,153 wells in the Pinedale Anticline in 2008, an increase of 791 wells since 2004. This equates to the drilling of about 515 new wells each year. Since 1995, the AQD has had a rigorous Title V inventory program, so the aspects of this well-by-well inventory development program focused on all aspects of the exploration and production of oil and gas. Production in the Jonah-Pinedale Area of Development (JPAD) based on the Annual 2008 UGRB emissions inventory was reported to be 843,284,082 mcf of gas and 7,091,145 bbls of condensate, more than double of that produced in 2004. With the increase in production ...