Independents looking to grow their gas-reserves profile should take heart-there's still plenty of gas left in the Rockies, according to a recent study by the Wood Mackenzie energy consulting team in Houston. During the past 30 years, estimates of Rocky Mountain gas reserves have grown from 19 trillion cubic feet (Tcf) to more than 57 Tcf, accounting for almost one-third of all domestic gas reserves in the Lower 48 states. Notably, the region holds 24 of the largest gas fields in the U.S., including five fields in the top 10: San Juan (No. 1), Pinedale (3), Jonah (6), Wattenberg (8) and Raton (9). The report notes that about 90% of these additions to reserves have come from extensions and revisions, predominantly in three states-Wyoming, western New Mexico and Colorado-and is correlated with technological advances in the industry. Most recently, major oils such as BP, Shell and ExxonMobil announced plans for expansion in the onshore Lower 48, the Rockies in particular. "Arguably, some of the benefits of ConocoPhillips' planned acquisition of Burlington Resources lie within the Rockies, including economies of scale in common basins and access to new plays," WoodMac reports. Meanwhile, E&P companies like Pioneer Resources, EnCana and Forest Oil have taken this strategy a step further by announcing plans to exit the Gulf of Mexico entirely to focus their resources on U.S. onshore development. "We found the real story of the Rockies to be a compelling tale of sustained growth and development; it's a region whose importance and profile in the U.S. gas-supply market continues to rise," says the WoodMac energy team. Examining the growth potential of the Rockies, the study team cites an Energy Information Administration forecast model that suggests gas reserves in the Rockies could increase to as much as 133 Tcf by the end of 2030. WoodMac's own internal modeling reaches much the same conclusion, suggesting that Rockies gas reserves could climb to as high as 138 Tcf during the same period. Significantly contributing to this growth will be the development of Colorado's Piceance Basin where tight-sands gas reserves are estimated to be upwards of 300 Tcf equivalent (Tcfe) in place-60% to 80% of that ultimately recoverable. Four key players in the basin-ExxonMobil, EnCana, The Williams Cos. and Bill Barrett Corp.-could produce up to 23 Tcfe of gas from a realistic 10-year development-drilling program on their total undeveloped Piceance acreage, the WoodMac study team suggests. Elsewhere in the Rockies, BP is planning to invest up to $2.5 billion in a multi-year drilling program at the Wamsutter development-agreement area in Wyoming's Greater Green River Basin. The plan includes drilling 2,000 wells in 15 years, the majority of them targeting tight-sands gas reservoirs. It's estimated that BP has around 2.5 Tcfe of remaining proved and probable gas reserves at Wamsutter. (For more on this, see "Whopping Wamsutter," Oil and Gas Investor, February 2006.) The study also cites Ultra Petroleum's activity on its Pinedale Anticline acreage in southeastern Wyoming where the producer has identified 2,867 drilling locations. Based partly on the assumption of future downhole spacing moving from 40 to 10 acres, Ultra has recently revised upward its proved-reserves estimate for Pinedale 32%, to 2 Tcfe, and increased its proved and probable reserve estimates 80%, to 6.3 Tcfe. The WoodMac study team says Wyoming-with its Big Horn, Greater Green River, Powder River and Wind River basins-is the single-largest source of gas reserves in the Rockies, accounting for 38% of the region's total. Pinedale, the third-largest gas field in the U.S., had total daily production in 2004 of more than 410 million cubic feet.

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