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Course 902 - Well Site Preparation and Drilling Safety

Safety guides and audits to make your job as a safety professional easier

Site Preparation Safety

site prep

Site preparation for an oil and gas well, in most instances, looks like any other construction site. OSHA uses Safety and Health Regulations for Construction [29 CFR 1926] to assess safety compliance during this phase of the development of a drilling site.

Once the location for the site has been established, the area is prepared for drilling, with the following steps:

  1. Site Preparation
    • leveling site
    • excavating and trenching
  1. Conductor hole, Rathole and Mousehole
    • conductor hole and pipe
    • rathole
    • mousehole
  1. Transporting Equipment
    • transporting equipment by truck
    • unloading at drill site

Leveling the Site


Before well drilling can begin, the company must clear vegetation, level the site, and construct a pad for the drilling rig and other equipment used in preparing the well. The site is leveled (if necessary) with a bulldozer and/or a grader.

Potential Hazards:

  • damaging buried pipelines and cables
  • unpredictable weather changes creating unexpected hazards
  • irritant and toxic plants, pollens, and other entrained materials
  • uneven ground causing bulldozers to roll over

Possible Solutions:

  • Perform a site line location survey.
  • Plan for hazards due to unpredictable changing weather.
  • After weather changes, conduct inspections for new hazards.
  • Protect employees engaged in site clearing from hazards of irritant and toxic plants. Teach the employees about available first aid treatments. [29 CFR 1926.604(a)(1)]
  • Provide rollover guards on all equipment used in site clearing operations. [29 CFR 1926.602]
  • Provide overhead and rear canopy guards on rider-operated equipment. [29 CFR 1926.604(a)(2)]

Excavation and Trenching


The scale and duration of excavating and trenching are very minor and site-specific. On some drilling sites, a below-ground-level cellar may be excavated. This is where the main borehole is to be drilled. A reserve pit and settling pits may be excavated and are used for water or drilling fluid (mud) discharges.

Potential Hazards:

  • Dust and other airborne contaminants can cause respiratory problems or allergic reactions.
  • Buried pipelines and cables can be damaged.

Possible Solutions:

  • Wear appropriate respiratory protection. [29 CFR 1910.134]
  • Perform a site line location survey.

Conductor Hole and Pipe

conductor hole

This is a large diameter hole, lined with pipe, also called a starter hole, varies in depth down of tens of feet to a few hundred feet depending on the local geology.

Some sites do not require a conductor hole.

Potential Hazard:

  • being struck by hoisting line or suspended drill or casing

Possible Solutions:

  • Wear Personal Protective Equipment: hard hats, safety glasses, safety toe boots, and work gloves. [29 CFR 1910.135], [29 CFR 1910.133], [29 CFR 1910.136]
  • Keep employees away if they are not working at this job.



A rathole is a hole in the rig floor, 30 to 35 feet deep, lined with casing that projects above the floor, into which the kelly is placed when hoisting operations are in progress.

This is either done by the portable rig that drills the conductor hole or can be done by the primary rig after rigging-up.

Potential Hazard:

  • falling or stepping into an uncovered rathole

Possible Solution:

  • Cover the hole until it is lined with casing or other material during rigging-up.


A mousehole is a shallow bore hole under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily placed.

This is either done by the portable rig that drills the conductor hole or can be done by the drilling rig after rigging-up.

Potential Hazard:

  • falling or stepping into an uncovered mousehole

Possible Solution:

  • Cover the hole until it is lined with casing or other material during rigging-up.

Transporting Equipment to the Site


Depending on the location of the well, access to the site may require preparation of a road bed. A site, and its access road, must accommodate a large number of temporary and semi-permanent structures and tanks, all brought in by truck. The tasks are:

  • transporting equipment by truck
  • unloading at drill site
Transporting Equipment by Truck

Equipment is loaded on trucks at the previous drill site or storage yard, secured and transported to the new drill location.

Potential Hazards:

  • At a newly prepared drill site, the soils may not be compacted sufficiently to support the incoming load. This could cause the load to become unstable.
  • The load may not be secured properly, causing it to shift or the tie-downs to fail.
  • In slick conditions, the truck may slide off the road.

Possible Solutions:

  • Make sure that the access road and drill pad at the drill site has been properly prepared before attempting to drive on it.
  • Drive slowly; always being cautious of shifting weight.
  • Loads should be tied down with proper devices and inspected before and during transport. U.S. Department of Transportation, [49 CFR 393.100] General rules for protection against shifting or falling cargo.
  • Always drive with caution, whatever the conditions.

Unloading at Drill Site

dog house

In this process, drill rig equipment is unloaded and placed approximately where it will be rigged up.

Potential Hazard:

  • Improperly secured loads could cause equipment to slide or collapse during unloading.

Possible Solution:

  • Inspect loads before loading or unloading.


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. During the site leveling process, all of the following are potential hazards, except _____.

2. Potential hazards in drilling site excavation and trenching include which of the following?

3. Which of the following is a large diameter hole, lined with pipe, and also called a starter hole?

4. Which of the following hazards is a associated with completing a rathole on a drilling site?

5. Which of the following is a solution to the potential hazard when unloading and placing drill rig equipment?

Have a great day!

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