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M. Ray Thomasson and Lawrence A. McPeek

Daniel J. Tearpock
Thomasson Partner Associates, Inc, Denver, CO

Eight of the ten Rocky Mountain Giant fields recognized since 1994 are examples of “by-passed economic pays”. Technological advancements were necessary to make them economic plays. Seven of these eight fields include: (1) in the Williston Basin – Cedar Hills - East Lookout Butte (estimated EUR 130 MMBO) and the new Middle Bakken play (estimated EUR 200-300 MMBO); and (2) five gas giants including Drunkard's Wash CBM (estimated EUR 2-4 TCFG), the Powder River Basin CBM (estimated EUR 24 to 27 TCFG), Pinedale (estimated EUR 10-20 TCFG), Jonah (estimated EUR 6-12 TCFG), and the Raton Basin CBM (estimated EUR > 1 TCFG).

In all of the above fields, the pay intervals were penetrated but not economic. The giant Cave Gulch field stands out as a by-passed field discovery which required neither new technology or increased prices to encourage an offset. The original 1959 well (Chevron #1 Waltman) encountered 78 feet of pay which was completed but some 132 feet of potential pay was not evaluated. By 1994 the early perforations in this well had produced 12 BCFG and 189 MBO. Dip meter data and subsurface control indicated up dip was to the northeast under the Owl Creek thrust plate but for 35 years no one had drilled the northeast offset. Early 2-D seismic could not confirm the structure. Lawrence A. McPeek of Thomasson Partner Associates, Inc., originated the Cave Gulch prospect using “old fashioned” subsurface work. Barrett Resources drilled the “rediscovery” and the rest is history.