Logging and mechanical services for deep sour gas wells in the Foothills of the Canadian Rockies require experience and stringent safety precautions.

Canada will continue to be a hot spot for drilling activity as its vast gas reserves continue to be exploited. But drilling for gas is not without its hazards.
"The Swan Hills formation along the Foothills of western Canada has a deep pool of 60% sour gas," said Brent Salmon, operations manager for Challenger Silverline, a business unit of Precision Drilling Corp. in Red Deer, Alberta. "Knowing that just 0.03% H2S can be lethal, safety and organization are paramount when conducting wireline logging and fishing operations."
Salmon speaks from personal experience. He witnessed the adverse affects of H2S as a young trainee at another wireline company, and since then has had a healthy respect for it. "Safety policies and procedures in place today far exceed those of 20 years ago," he said.
Challenger Silverline has stringent safety measures, beginning with the proper training of crew members. It usually takes trainees a minimum of 2 years before they qualify as junior operators able to work without immediate supervision. "It's one thing to work in the high-pressure conditions of the Foothills and another to work in low-pressure areas such as eastern Alberta," said Salmon. "Wireline operators working in sour gas conditions have to be well-trained. Some wells may have 10,000-lb surface pressures and exceed 20,000 ft (6,100 m) in depth. At those depths, maximum downhole equipment tolerances are carefully monitored to ensure successful wireline operations."
At Challenger Silverline, all crew members attend industry-standard training courses in H2S, first aid, handling of dangerous goods and more. If an emergency should arise, each crew member knows his role and what actions to take. "On one occasion," said Salmon, "a ring gasket failed on the wellhead, causing a release of sour gas. Our employee, who was under mask at the time, calmly closed the master valve, stopping the leak. He exited the large cloud of H2S gas unscathed due to his protective equipment and training.
"Before a crew even leaves for the job site, we review safety-related issues, including the type of rig being used, the location, well conditions, weather, you name it. We also review our past experiences working in that particular locale. And then, as soon as a crew arrives at the job site, they conduct a safety tailgate meeting. A comprehensive checklist is reviewed concerning the lease itself, possible hazards and other safety issues. All workers are required to wear gas masks and must be clean-shaven to assure a proper facial seal. They must also situate their equipment upwind of any potential gas release. This also involves constant monitoring of wind direction, which can change at any time in the Foothills. We have to keep a close eye on the windsock."
Dan Salmon, Brent's brother and Red Deer manager, added, "Customers with these high-profile wells know we cannot cut corners on these jobs. For example, it is our policy to always run a drift gauge ring prior to running certain types of downhole pressure-control equipment. This ensures that the tubing is clear of any restriction or obstruction. We left a job site once after a customer refused our request to run a gauge ring prior to setting a hook-wall plug, allowing the service rig to remove the blowout preventers. Consequently, another wireline company was called in, and the hook-wall plug got stuck across the valve, resulting in an expensive freezing/fishing job."
Added Brent Salmon, "When tools are lost downhole, a bad situation is often made worse by improper attempts at recovery." He added the best way for an oil company to avoid the need for killing a well or bringing in a service rig is to order a reputable wireline company immediately for fishing operations.
He explained that if a specialized tool does not exist, existing tools may be modified. "There was one occasion when a customer called to say a plug could not be pulled out of the hole due to scale and debris problems. We suggested they knock it out the bottom, then jet-cut the tail pipe off as required. A special tool was built at a local machine shop to facilitate knocking the plug out. It worked on the first attempt."
The two men recalled the time they went to the scene of a high-pressure H2S well where another wireline company could not keep a seal on their line. They rigged up their own equipment and wireline unit consisting of dual grease injectors and a special synthetic grease. It took 72 hours working around the clock to complete the operation.
"On another job," said Dan Salmon, "two of our crews in alternating shifts spent 14 days recovering pieces of a broken grapple that the customer had tried to fish. And we wouldn't have been able to do the job in that amount of time using a conventional approach. Our solution was to use 'met-spec.' This is a liquid that is heavier than metal; it looks like mercury. You pour it down the hole and it gets underneath the metal pieces and floats them up where you can retrieve them.
"We dump-bailed met-spec onto the fish. And then it took 150 descents to 12,000 ft (3,660 m) with chisels and magnets before recovering everything. It was all done without incident. The production string was then reset."
Challenger Wireline was one of the first companies to field combination electrical and mechanical wireline trucks. "These trucks give us a lot of versatility. With one unit on location, we can bond log, do tubing-conveyed perforating on the well, rig up slickline and do the mechanical services (plugs, recorders, etc). When well conditions do not allow for the setting of a mechanical slickline plug, we are capable of setting a permanent bridge plug below the packer on electric line."