Date of incident: March 2024
Notice of incident number: 2024170090013
Employers: Wellbore drilling company; natural gas producer (lease holder)

Incident summary
Workers at a remote oil and gas wellsite were preparing a drilling rig for transportation. As the workers were closing one of the large swing-out arms on the drilling rig, two 544 kg (1200 lb.) floor plate extensions fell from approximately 4.9 m (16 ft.) to the ground below. A worker was struck by one of the falling plates and sustained serious injuries.

Investigation conclusions

Cause

• Floor plate extensions disconnected from substructure and fell. Workers were disassembling the drilling rig substructure and attempting to close the swing-out arms with the floor plate extensions still attached. As the swing-out arms were closing, they pushed against the bottom of the floor plate extensions, which raised up and off of the J-hooks connecting them to the substructure.

Contributing factors

• Missing securing pins. The wellbore drilling firm’s engineers designed and modified the floor plate extensions. The engineering drawings clearly show securing pin pockets on the substructure and the floor plates; however, the firm did not ensure that the securing pins were in place during assembly. At the time of the incident, the securing pins were not installed. Had the floor plate extensions been properly secured to the substructure with the designed securing pins, the likelihood of the floor plates falling would have been reduced.
• Incomplete assembly and disassembly instructions. The wellbore drilling firm did not develop or provide specific assembly or disassembly instructions to the workers who were relocating the drilling rig and who were unfamiliar with the modified substructure. Had the drilling firm provided complete disassembly instructions, the workers would have been aware that they were required to remove the floor plate extensions before closing the swing-out arms.
• Inadequate supervision.
  • The wellbore drilling firm failed to provide the workers with assembly and disassembly instructions or provide any detailed information on the modifications to the substructure and new methods for disassembly, putting the workers at risk.
  • The lease holder failed to ensure that workers were aware of all assembly and disassembly instructions and that they adhered to them. The lease holder also failed to ensure compliance with the Occupational Health and Safety Regulation as it pertains to following the manufacturer’s instructions to make sure the swing-out arms are closed for transport.
• Inadequate hazard identification and risk assessment. The wellbore drilling firm did not conduct a risk assessment for the modified substructure, nor did it identify the overhead hazards of the modified floor plate extensions. Had the firm identified hazards and conducted a risk assessment, it would have been able to implement safe work procedures specific to the disassembly of the substructure and implement hazard controls to minimize the risk of injury to workers.

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