Wyoming's deep Hilliard shale in evaluation

July 11, 2006
Gasco Energy Inc., Englewood, Colo., farmed out an interest in its Daniel Anticline Prospect in the northern Green River basin to private Dallas independent Hunt Petroleum Corp.

By OGJ editors
HOUSTON, July 11 -- Gasco Energy Inc., Englewood, Colo., farmed out an interest in its Daniel Anticline Prospect in the northern Green River basin to private Dallas independent Hunt Petroleum Corp.

Gasco as operator obtained a drilling permit for a 16,500-ft exploratory test, the Cottonwood Ranch 24-21, in Sublette County to test overpressured tight gas sands in the Cretaceous Lance, Mesaverde, Ericson, Rock Springs, and Hilliard shale formations. Completed well cost is estimated at $8 million.

Gasco is seeking a rig and is guardedly optimistic it will spud the well in 2006. Hunt Petroleum will earn as much as a 50% interest in the prospect.

The 3D-defined Cottonwood Ranch 24-21 will be a 1-mile offset to the Grindstone Butte 41-16, drilled by Burlington Resources Inc. in late 2001. It tested 3.2 MMcfd of gas from Erickson at 11,500 ft. It is also near a well that produced gas from the Lower Lance.

Gasco controls 39,000 net acres in the area.

The drill site also is 12 miles west of the north end of giant Pinedale Anticline field, where the Questar Corp. 15-29 Stewart Point well went to TD 19,520 ft in 2005 and had gas shows in the Rock Springs and Hilliard formations (OGJ Online, Sept. 9, 2005).

After applying a three-stage frac to 900 ft of Hilliard at 18,500-19,400 ft, Questar gauged sweet, dry gas at the calculated rate of 10.7 MMcfd in 32 hr and encountered severe wellbore plugging by chunks of shale, proppant, and frac plugs and shut-in pressures as high as 13,500 psi.

This appears to have been industry's first attempt to frac and produce from shale at these depths and pressures, Questar said.

After a winter break, the company was reentering the well earlier this year to retest the Hilliard and later evaluate Rock Springs intervals at 16,000-18,000 ft.