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How Injuries Occur in Drilling Operations

wellsite fire

The potential that an accident may occur on a drilling rig is inherent in all tasks. However, the probability or likelihood that an accident can occur may be greater for some tasks than for others. Depending on “luck” more than anything else, the severity or degree of the injury will vary with each injury accident.

The old saying, “It’s not the fall that kills, it’s the sudden deceleration,” is very true. Injury severity is reflected by the nature of the injury (amputation, fracture, laceration) and by the amount of time the injured employee is unable to work.

Injuries that result from hazards unique to oil and gas well drilling operations can be broadly classified into two major categories:

  1. those injuries incurred from task-specific accidents
  2. those injuries incurred during more catastrophic events such as blowouts, derrick collapse, and hydrogen sulfide exposures.

Drilling Rig - DOE

Task-Specific Accidents

The first major category of accidents is representative of incidents that occur during task-specific operations. This major category has been further subdivided into accidents:

  1. that occur during drilling operations,
  2. derrick tasks, and
  3. materials handling activities.

Drilling Operations

Drilling operations have been further categorized by the tools or equipment used in performing the task, such as hazards associated with:

  • Slips
  • Tongs
  • Elevators
  • Catlines
  • Working surfaces
Pulling and setting the slip.

Hazards associated with Slips

Slips are the toothed wedges that are positioned between the drill pipe and the master bushing/rotary table to suspend the drill string in the well bore when it is not supported by the hoist.

Most of the accidents attributable to slip operations occur in relationship to materials handling; strained backs and shoulders are common. Furthermore, the working surface may be wet and slippery, contributing to muscle strains, as well as to accidents such as falls and dropping the slips onto the feet.

Lack of communication between the driller and the employees engaged in the slip operations and lack of coordination between employees engaged in the task also contribute to accident potentials in slip handling.

Drilling connection using slip, Kelly, chain and tongs.

Hazards associated with Tongs

Tongs are the large, counterweight-suspended wrenches used to "break out" the torqued couplings on the drill pipe.

Both sets of tongs have safety lines; when breakout force is put on the tongs, employees should step back from the outside radius of the tongs in the event a tong slips or a safety line slips or breaks. In these instances, employees positioned in the path of travel can suffer serious injury.

Another likely accident can occur when the driller actuates the wrong tong lever and an unsecured tong swings across the rig floor at an uncontrolled velocity. Sometimes the wrong lever is pulled because the levers are not placed in such a manner as to make them readily distinguishable, and sometimes because the driller is distracted or fatigued.

A common accident attributable to tongs can occur when an employee has his hand or finger in the wrong place as he attempts to swing and latch the tong onto the drill pipe resulting in crushing injuries and amputations of the fingers.

Solo drilling connection. Elevator clamps at .45 sec.

Hazards associated with Elevators

Elevators are a set of clamps affixed to the bails on the swivel below the traveling block. They are used to clamp each side of a drill pipe (the pipe is belled in this area) and hold the pipe as it is pulled from the well bore.

A number of accidents and associated injuries can occur during the latching and unlatching tasks--fingers and hands can get caught and crushed in the elevator latch mechanisms.

The more severe injuries involve improper attachment of the pipe to the elevator. If the pipe is overhead when the latching mechanism fails, then the pipe may fall on employees working on the drill floor.

Hazards associated with Catlines

Catlines are used on drilling rigs to hoist material. Catlines and high lines should be designed to safely lift or otherwise handle the loads. The revolving cathead on the drawworks powers the friction pulley system. An employee wraps a rope, usually 1-1/4 inches in diameter, around the cathead and tensions the line. The tighter the rope and the more wraps around the cathead, the faster the material is hoisted.

Accidents that occur during catline operations may injure the employee doing the rigging as well as injure the operator. Minimal hoisting control causes sudden and erratic load movements, which may result in hand and foot injuries.

Safety measures:

  • The maximum allowable working loads should be based on manufacturers' tables .
  • A post or guard should be provided to deflect cathead lines away from the driller' s position . Where posts are of the rotating type, the top and bottom ends should be guarded to contain the post in case the shaft fractures.
  • A catline grip should be provided and used to keep the catline tight when the line is not in use.

Hazards associated with working surfaces


The OSHA standards for walking/working surfaces apply to all permanent places of employment, except where only domestic, mining, or agricultural work is performed.

The rig floor is the working surface for most tasks performed in well drilling operations. This surface is frequently wet from circulating fluid and/or water used to wash it down. Prevailing weather may further increase the slipperiness of the surface.

Employees must lift, push, and pull heavy items as a routine part of their assignments. Slippery working surfaces can increase the likelihood of back injuries and other overexertion injuries. Slips and falls may result in sprains, strains, contusions, and lacerations. Exposed moving parts (rotary table and kelly bushing) may compound the injury potential and severity.

Additionally, the rathole (although usually an elevated tube) and mousehole, used to temporarily store the kelly bar and drill pipe, may be uncovered when not in use. Stepping into a floor hole can result in fractures and sprains.

The cellar is a pit in the ground below the derrick structure. Hydrogen sulfide, if released, and water may accumulate in this low area. Ladder access into the cellar is a potential accident source, as is lack of proper guarding.

Optional Video

Watch this U.S. Chemical Safety and Hazard Investigation Board (CSB) training video for the onshore drilling industry detailing lessons learned from the January 22, 2018, blowout and fire at the Pryor Trust gas well in Pittsburg County, Oklahoma, that killed five workers.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Which of the following are the large, counterweight-suspended wrenches that can cause serious injury if an employee is positioned in the equipment's path of travel?

2. Which of the following pieces of equipment is used to hoist material and usually causes injury to operators and those doing the rigging?

3. The cellar is a pit in the ground below the derrick structure. Which of the following may accumulate in this low area?

4. Which of the following pieces of equipment will cause the drill pipe to drop if it fails causing serious injury?

5. A catline _____ should be provided and used to keep the catline tight when the line is not in use.

Have a great day!

Important! You will receive an "error" message unless all questions are answered.