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Oil and Gas Well Drilling and Servicing eTool

Site Preparation Conductor Hole, Rathole and Mousehole

JSA
Figure 1. Conductor hole

Figure 1. Conductor hole

Prior to commencing the rig-up process, the conductor, rathole and mousehole are completed. Special companies may be hired to begin drilling these three holes.

Hazards may be related to the following:

Figure 2. Installing conductor hole casing

Figure 2. Installing conductor hole casing

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:

Figure 3. Rat hole - covered

Figure 3. Rat hole - covered

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.
Figure 4. Mousehole - covered

Figure 4. Mousehole - covered

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.

#49. Rathole

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

Rathole

#43. Kelly

The heavy square or hexagonal steel member suspended from the swivel through the rotary table. It is connected to the topmost joint of drill pipe to turn the drill stem as the rotary table turns.

Kelly Photograph Kelly Illustration

#46. Mousehole

Shallow bores under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily suspended for later connection to the drill string.

Mousehole
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