Petrobank Energy & Resources Ltd., Calgary, is testing two strategies to expand the combustion zone and raise production in a pioneering thermal heavy-oil project in Saskatchewan.
The THAI process produces bitumen through horizontal wells with vertical air injection wells drilled near their toes. The injected air supports combustion that mobilizes and upgrades bitumen, which drains into the production well. The combustion zone expands from the toe of the horizontal well toward the heel.
In its quarterly financial report, Petrobank said average Kerrobert production dropped to 135 b/d in the second quarter from 205 b/d in the first quarter and 236 b/d in second-quarter 2012.
The company said its challenge is to form “a well-structured THAI combustion front at the top of the reservoir.” It believes permeability channels have formed in the reservoir that flow from the upper combustion zone to the bottom of the reservoir.
“Injected air preferentially follows these channels rather than staying at the top of the reservoir, slowing the formation of a large THAI combustion zone,” the report said.
One of its strategies involves coinjection of water in several wells.
“The water is intended to alter the relative permeability in the channels to redirect air flow, keep air at the top of the reservoir, and to help transfer heat horizontally across the reservoir,” the company said.
Petrobank also has drilled two multi-THAI air injection wells associated with two horizontal production wells. Drilling of one or more injection wells along a horizontal producer expands the combustion zone and causes more the reservoir to drain into the production well.
“Steam preheating has started on these injection wells, and we intend to initiate air injection in September,” Petrobank said.
At its Dawson demonstration project in Alberta, the company began cold production from two horizontal THAI production wells late last year, achieving combined output of about 10 b/d in the second quarter this year. It has shut in the wells and applied to Alberta Energy Regulator to start two cyclic steam stimulation (CSS) cycles through the THAI production wells.
“We believe that CSS will be more effective in preconditioning the reservoir for THAI as CSS should result in more voidage than conventional cold production,” Petrobank said.
The company reported a second-quarter loss of $4.151 million, compared with a $4.282 million loss in the comparable quarter of 2012.
Saying the Kerrobert project will take longer than expected to reach breakeven, it lowered its forecasts of 2013 capital expenditures to $16 million and of operating costs, maintenance capital, and general administrative costs to $26 million, both down $7 million from earlier estimates.