The US Department of Energy said a successful horizontal well it helped sponsor in the Green River basin of southwestern Wyoming could encourage nonconventional gas exploration in the Rocky Mountains.
Last April, Union Pacific Resources Group Inc. (UPR) drilled a 17,000-ft well with a 1,700-ft horizontal section. In drilling the well, UPR used fracture imaging and advanced drilling technologies developed by DOE and GRI. Production from the well exceeded expectations, with more than 2.1 bcf of gas produced in the first 6 months of operations.
UPR is now drilling two horizontal wells into the same formation. DOE said more wells are likely, and if they achieve comparable production, they could generate almost $10 million in federal and state royalties, almost double DOE's investment.
DOE said that, before its Greater Green River Basin Production Improvement Project began in 1995, little work had been done to define the geologic and production characteristics of the tight, fractured Frontier formation. The gas-bearing zone covers 900 sq miles and has potentially huge reserves.
DOE will pay half the $546,000 cost for core samples and logging runs on UPR's new wells, gathering geophysical data such as porosity, resistivity, water saturation, and magnetic resonance.
Last April UPR drilled the Rock Island 4H in Sweetwater County. It initially flowed 14 MMcfd of gas and now is producing 9.5 MMcfd. DOE said, during drilling, a record 77 ft of horizontal core was collected.
The new wells are Sidewinder 1 and 2. DOE said Sidewinder 1 recovered a promising 50 ft core from a true vertical depth of 15,493-99 ft below the surface, making it the deepest horizontal core ever recovered.
"About 50% of the fractures had slickenslides-a polished, slightly ribbed surface indicating movement caused by a fault," said DOE. "Most of the open fractures were lined with tiny fine-grained crystals (euhedral quartz crystals) that suggest the fractures are quite large.
"All but four of the fractures have an east-west strike orientation, which indicates drilling should proceed in a perpendicular north or south direction to intersect as many fractures as possible and maximize gas flow."
DOE said Sidewinder 1 was drilled on the up side of a fault, as was Rock Island 4. Sidewinder 2 is on the opposite side of a major regional fault, where the faulting pattern may be different.
