Reverse circulation drilling technology has yielded commercial gas flows from the shallow Cretaceous Bow Island formation 57-100% higher than rotary air drilled wells, said K2 Energy Corp., Calgary.
The results are based on extended flow tests at four wells in northwestern Montana.
K2 said the technology, combined with carbon dioxide frac jobs, may allow it to economically develop enormous shallow gas accumulations with producing lives as long as 30 years that have remained untapped because of damage from conventional drilling methods. Trillions of cubic feet of gas are in place in the region.
The firm is confident that stabilized rates exceeding 300 Mcfd are achievable with multizone stimulations, allowing recovery of capital costs within 12 months of production start-up.
The developments represent a major kickstart to the shallow gas play on the west flank of the Kevin-Sunburst dome. K2 has a large acreage agreement with the Blackfeet Indian Tribe on the reservation, which blankets eastern Glacier County. K2 holds operating rights on several hundred thousand acres in the area, where Bow Island is generally encountered at 2,000 ft or less.
Bow Island drilling
K2 said it uses a hard rock mining rig and adapted its reverse circulation center sampling technology for shallow, low-pressure gas drilling in the Bow Island formation.
"Based on current capital costs for reverse circulation drilling, multizone stimulations and well completions with $2 (US) gas pricing, capital costs are recovered within 12 months of commencement of production," K2 said.
The drilling contractor, Midnight Sun Drilling, Whitehorse, Yukon, uses air hammers and dual wall drill pipe that consists of a 27/8 in. string inside a 41/2 in. string. Air is circulated down to activate the air hammer and back up the 27/8 in. pipe, nearly eliminating drilling damage to the formation, K2 said.
Gas can flow during drilling, and which zones are flowing is certain.
K2 said nine Bow Island wells flowed 900-BTU gas to surface and encountered no formation water. Net pay averaged 52 ft, with porosity ranging from 6-24%.
Trican Well Servicing, Calgary, applies unique CO2 fracs to improve productivity of zones with 6-12% porosity. The companies worked with various regulatory authorities in the US for 15 months.
K2 in late February said the Palmer Bow Island 11-5 well, reverse circulation drilled and with only one of the four Bow Island zones perforated and stimulated with CO2, flowed a sustained 115 Mcfd. Walleye 5-5 flowed 73 Mcfd from one zone, and the Atlantic 3-5 well test failed due to previous rotary air drilling damage.
A US Department of Energy representative witnessed drilling and stimulation operations and expressed interest in a possible cost-shared joint venture to further prove the technology on other formations within K2's land holdings.
K2 was writing down its shallow oil operations in the area in order to focus on gas development.
