On January 13, 2012 in the rural Garrington, Alberta field Midway Energy Ltd. hydraulically fractured a horizontal well bore at a depth of 6,069 feet (1850 m) which caused a surface blowout of a nearby Wild Stream Exploration Inc. vertical oil well also completed at 6,069 feet. Alberta's Energy Resources Conservation Board (ERCB) investigated the incident and has publicly released its investigation report.
The ERCB noted that segments of the Midway wellbore where four fracture stages were conducted were only 423 feet (129 m) apart. The Board determined that the four fracture treatments took place between 12:08 pm and 1:17 pm and that one of these stages was most likely to have communicated with the Wild Stream well.
Significant decreases in hydraulic fracturing pumping pressure can be an early indication of interwellbore communication but did not occur in this case. The first sign of communication was at approximately 3:00 pm at the connected Wild Stream production battery where there was a sudden increase in gas pressure. The compressor went down and it was later learned that the fuel gas supply had been contaminated with nitrogen gas, a component of the Midway fracture fluids. At approximately 4:30 pm a member of the public reported fluids and an oil mist being discharged at the surface from the Wild Stream well, fouling an area of about 650 by 750 feet.
The ERCB found in its investigation that Midway had failed to follow its internal protocol which modeled the fracture size and the separation distance from other wells. To design its frac, Midway used a general frac model for the Garrington field. Based on that model, the company's protocol was to space fractures from adjacent wells at 1.5 times the modeled half length of the fracture. For this well, Midway used an estimated 260 to 295 foot (80 - 90 m) frac half length. Midway's protocol called for spacing at 442 feet (135 m). As the Wild Stream well was a close as 423 feet (129 m), the ERCB found this error to be the root cause of the incident.
It also found that the surface piping, discharge hoses, fuel gas lines and pressure relief valve on the Wild Stream well were not pressure rated to withstand the pressure required for hydraulic fracturing. Also, Midway did not notify Wild Stream before beginning its fracturing operations. At that time, there was no regulatory requirement in Alberta to notify nearby well owners.
The Board also found that the companies managed their response to the incident appropriately, potential environmental damage was promptly mitigated and that the incident did not impact the public, livestock groundwater or surface water bodies. The Board also reminded the public that this type of incident is vary rare in Alberta. More than 171,000 oil and gas wells have been hydraulically fractured in Alberta since the 1950s. In recent years, more than 5,000 multi-stage hydraulic fracturing operations have been conducted in horizontal wells in Alberta.
The ERCB did not bring any enforcement action against Midway or Wild Stream as they had not violated any regulations then in place. However, 10 days later the Board released Bulletin 2012-02-Hydraulic Fracturing: Interwellbore Communication between Energy Wells requiring operators, among other things, to undertake fracture propagation modelling and notify offset well owners. Since then the ERCB has also released for public comment a draft Hydraulic Fracturing Directive to regulate subsurface aspects of hydraulic fracturing.
This article was prepared by Barclay R. Nicholson (firstname.lastname@example.org or 713 651 3662) from Fulbright's Energy Practice.