Canadian producers heaved sighs of relief when a blowout of “sour” natural gas, laced with lethal hydrogen-sulphide, was capped according to a plan devised by a Texas master of wild well control without causing serious injuries on the western boundary of the Alberta capital of Edmonton.
The embarrassing accident promptly lost its high public profile, leaving well owner Acclaim Energy Trust, its contractors and the Alberta Energy and Utilities Board to conduct a post mortem inquiry expected to sort out exactly what happened and what new precautions, if any, might have to be adopted in future.
There was only one sure bet, suggested the celebrated expert that Acclaim imported from Amarillo to devise and supervise the well taming effort. No one is going to guarantee such an accident will not happen again, said Bob Grace, whose GSM Inc. has tamed blowouts from Kuwait to Vietnam in the two decades since it devised the modern technique of corralling runaway gas with relief wells.
“Blowouts will be around as long as the business will be around,” Grace predicted in an interview. He described runaways as an occasional price of producing fossil fuels under often difficult and unpredictable conditions.
“There is no foolproof way to drill a well. It’s the nature of the beast. It’s miles underground, under high pressure, with people and steel and complicated equipment involved. There’s also no foolproof way to drive a car or fly an airplane.”
It is Canadian producers’ hard luck that nature has given them an extra cross to bear, Grace added. Odds are higher than anywhere else on the planet that an accident will involve a substance that strikes fear into the public and the industry, hydrogen-sulphide.
The Edmonton accident was only the latest in a string of examples of a comparatively minor field accident turning into a major case of defending the industry’s credibility and some of its best drilling targets because the blowout involved sour gas.
The central role of sour gas in Canadian supplies is extensively documented by the AEUB and a specialized group of industry, citizen and government representatives it set up to run a years-long review of the field, the Alberta Public Advisory Committee on Public Safety and Sour Gas.
The province has a vested interest in the issue. About 20% of Alberta natural gas reserves and 26% of production contain hydrogen-sulphide in concentrations exceeding .01% (100 parts per million) and averaging 9.2% (92,000 ppm). Of the provincial government’s annual gas royalty income, currently about C$6.8 billion (US$5.4 billion), 26% comes from sour-gas production. About 37,000 Alberta jobs, paid C$1.3 billion (US$1 billion) in annual wages and salaries, are sustained by sour-gas production in 50 municipalities and 200 processing plants.
Unlike carbon-dioxide, greenhouse-gas emissions and global warming, hydrogen-sulphide in sour gas is recognized by all as an immediate hazard. There are no arguments, especially from the producers and field contractors who deal with the stuff around the clock every day.
Human noses turn up at the rotten-eggs odour of hydrogen-sulphide in trace amounts of one part per million. Exposure to 100 ppm, the level where occupational health and safety regulations require workers to wear protective gear, deadens the warning sense of smell. Inhaling 1,000 ppm, or one-tenth of one per cent, causes immediate unconsciousness, then death unless rescue arrives promptly.
At 370 ppm hydrogen-sulphide, Acclaim’s Edmonton gas blowout prompted evacuation of about 700 nearby residents and the smell was the talk of neighborhoods far downwind of the site.
But there is also no doubt that the Canadian gas industry needs to keep its access to sour deposits in order to maintain supplies. When Shell Canada announced the biggest Alberta gas find in 18 years just before the Edmonton well blew out on Dec. 12, the company disclosed that the discovery of up to 800 Bcf of reserves beneath wooded foothills near Rocky Mountain House was 35% (350,000 ppm) hydrogen-sulphide. Sour drilling targets pervade the Canadian industry’s most prospective region, the east slopes of the Rocky Mountains running through western Alberta and northeastern British Columbia. Another recent discovery, drilled by a partnership between Shell and Talisman Energy Inc. in B.C., is sour.
The silver lining to the Edmonton blowout was that it showed the industry has evolved effective techniques for dealing with accidents. For most of the 30 days that the 1 MMcf/d leak lasted, the hydrogen-sulphide was rendered safe by igniting the gas in a controlled burn. That procedure, an industry standard, incinerates the poison and converts it into much less lethal sulphur-dioxide. Instead of rotten eggs, nearby areas at most endure an odor akin to the much less harsh, mildly sulphurous smell left after blowing out a match.
Corralling runaway gas with relief wells was learned the hard way from a Texas disaster, recalled Grace. At a site on the Panhandle “we explored all the technology. We failed miserably.” This grand daddy of Texas blowouts, a well called Apache Key, was about 16,000 feet deep and took 18 months to bring under control in 1982-83.
Alberta’s worst well disaster, the Lodgepole sour-gas blowout southwest of Edmonton in 1982, lasted 67 days. Texas geology forced Grace and his GSM, to invent a way to drill “deviated” or oddly angled relief wells with pinpoint accuracy. The rock was too “tight” or dense to use traditional methods of drilling relief wells just into the vicinity of blowouts then siphoning gas away from the underground formation. It was essential to intercept the problem well bore.
In Texas at Apache Key, Grace’s target was a well bore only five inches wide. The Edmonton target was a seven-inch well bore about 5,700 feet down. In such situations the underground target’s exact location cannot be predicted from the surface. “No well ever drilled is straight,” Grace said. Uneven rock, combined with variations in the behavior of machinery and crews, make drill bits stray off mathematically true vertical courses. The deeper a well, the more it meanders. The bull’s eye sought by a relief well is typically hidden anywhere in a band up to 200 yards across, Grace said.
He developed a reliable way to probe for underground targets with a drilling rig by harnessing a system known among scientists as “active magnetics.”
Devised by Cornell University physicist Arthur Kuckes, the method finds well bores by sending electric current through rock to detect magnetic fields of steel pipe. The technique works at distances of up to 100 yards and since its first industrial use for the Texas blowout has become the cornerstone of a technology firm based in Ithaca, NY, Vector Magnetics.
Parallel advances in steering drill bits enable Grace to direct a relief well crew to the right spot reliably once he completes other aspects of a blowout control plan using computer modeling techniques.
“They can put that thing in your hip pocket if that’s where you want it. They’re really good,” Grace said.
The relief well that stopped Acclaim’s blowout followed an S-shaped course through the ground. Grace has frequently been called into action in Alberta. He taught drilling technology in Calgary for 20 years. He has written textbooks on drilling practices and blowout control. He devised and supervised the program when the AEUB and industry collaborated in 2003 on a C$5 million (US$4 million) job of stopping Alberta’s longest and most complicated blowout. It was a celebrated well called Old Salty that spewed toxic water and gas for 87 years near Peace River in the northwestern part of the province. The job was exceptionally complex because the blowout’s out-of-control flows included two previous relief wells that were drilled with previous technology and failed spectacularly.
Grace’s blunt realism about gas field accidents was promptly proved right after he finished the Edmonton job. The industry keeps giving him work.
Within hours of bringing the Edmonton runaway under control, Grace was on his way to a bigger gas blowout in Bangladesh.
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