Report Released in Well Explosion Incident

Lynsey Kitching

Lack of experience and adequate well control procedures was the root cause of the latest well incident report released from the BC Oil and Gas Commission (OGC). The report was posted last week, about a year after the incident.

Though the report, like most other industry reports uses very technical words to try and dilute the situation, the reality is the well blew up, and toppled over.

On Feb. 4, 2012 Suncor Energy Inc. (Suncor) commenced drilling a Montney gas well, about 30 km north of Hudson’s Hope. The drilling contractor was Nabors Drilling Canada.

The incident took place on Mar. 9, 2012 in the evening when an alarm began to sound. What the workers found was a drastic increase of drilling volume, about 0.5 cubic metres at a depth of 2,124 meters. The crew proceeded to shut in the well by closing the blowout preventers. At this point the fluid volume gain was seven cubic meters and the casing pressure had exceeded its maximum of 14,400 kilopascals (kPa) to 14,174 kPa.

In attempt to lower the pressure, the crew opened up the well to flow. This didn’t work and the casing pressure continued to increase. At this point there was one rig member in the manifold shack, trying to make valving changes and a second member was on route to help.

The crew heard a loud bang and fluid began to flow through the door of the manifold shack.

In an article published on drillingahead.com this piece of the puzzle goes a little differently (check out the Tumbler Ridge News website for a link to the video).

The eye witness states there was actually flames entering the room, not fluid. Either way, the two members managed to escape through a different door.

At this point the emergency has been going on for about 40 minutes and the pressure in the casing is now at 27,000 kPa almost double that of it’s maximum.

The crew was then evicted, just before the drilling rig caught fire and was subsequently destroyed.

Suncor dispatched an emergency response plan and safety/well control experts to the site. The OGC was notified about 15 minutes after the fire began at 11:33 p.m.

One of the main worries was the potential for hydrogen sulphide (H2S) or sulphur dioxide (SO2) to be in the air, so Suncor and the OGC dispatched air monitoring units who found after having monitored the area for a month a half there was no hazard to air quality. The report states, “The maximum recorded SO2 concentration at the wellsite was 15.3 ppb on April 11. The WorkSafeBC short-term exposure limit for SO2 is five ppm (5,000 ppb).

During the blowout, the upper portion of the well was damaged and by damaged the OGC means completely destroyed. Also, due to high velocity flow, a hole eroded in the casing at a depth of about five meters below ground level. To help minimize the damage to soil, an area around the wellbore was excavated to 11.3 meters.

The report states, “During the incident, an unknown quantity of invert drilling fluid was spilled on the lease. The invert ignited during the fire, leaving a solid residue on the soil. Approximately 375 tonnes of soil and invert residue was stockpiled and later trucked to the Tervita Silverberry landfill.”

The environmental consequences continued on March 16, 2012. The report states, “A 1.5 cubic meter spill occurred while transferring drilling fluid from a storage tank located at the wellsite. Approximately one cubic meter was recovered as a liquid and the remaining 0.5 cubic meterswas absorbed using sawdust.”

More soil was taken to the landfill about a week later because when “the fire was extinguished small quantities of produced liquids were intermittently released from the wellbore. Due to excavation in the vicinity of the well, it was not possible to contain the produced liquids. Any impacted soils were removed immediately and added to the soil stockpile for disposal.”

The nearest stream is Farrell Creek, located about 150 m to the northwest of the wellsite boundary. The entire wellsite was bermed prior to the start of drilling and the OGC claims all spilled material was contained on site.

According to the BC Water Wells Database, the nearest water well is located about 8.2 km to the west of the site.

By May 16, 2012 Suncor put a plug on the operation and began to demobilize the site.

The OGC says lack of training and procedures caused the loss of well control. The report concludes, “Had a clear procedure been in place to respond to well control events where the casing pressure approached or exceeded MACP, it is unlikely well control would have been lost.”

The report also points to experience being a contributing factor to the episode. “The drilling rig crew’s experience was primarily with heavy oil wells in eastern Alberta. While the crew had received specialized well control training on site, they did not have any significant experience drilling deep, high-pressure gas wells. As the incident progressed, the rig crew’s actions defaulted to their previous training and experience,” the report continues, “The Managed Pressure Drilling (MPD) program stated the MPD equipment should not be used if the casing pressure exceeded (>90 percent of posted MACP) 12,960 kPa. Casing pressure exceeded this threshold and the rig crew should not have been attempting to conduct well control operations through the MPD equipment.”

The OGC also concluded the drilling fluid return line on the MPD system failed. It is believed this failure resulted in the loss of well control.

The OGC investigation had one positive to say and that was in regards to Suncor’s emergency response. The Report said in regards to this, “The Commission is satisfied that Suncor’s response to the incident was timely and appropriate.”