Air Rotary Drilling

[Narrator]: The Air Rotary and
Down-the-Hole drilling systems

are similar in design and function with
the main difference being

the latter system having the additional
cutting action of the air driven hammer.

First, we will profile the
Air Rotary system

followed next by the Down-the-Hole
Hammer.

The Air Rotary drilling system is
primarily designed

for drilling in consolidated formations,

offering good penetration rates and quick
cuttings removal.

This system usually consists of a truck
mounted drill

and separate support vehicle which carries
supplies required for the drilling process,

such as water and welding equipment.

If the horsepower requirements for the
truck are similar

to the horsepower requirements
of the drill,

one engine can be used for both by
utilizing a transfer case.

This rigs equipment includes an
air compressor

and both water and mud pumps to help
facilitate the removal of cuttings

depending on the geology encountered.

Please note, for demonstration purposes,
no surface casing is being used

to better illustrate these processes.

Air Rotary drilling systems can utilize
a number of cutting actions:

rotary crush, rotary cut,
or rotary percussion.

Shown here is rotary crush action.

The flushing medium used is dictated
by the geology, and options include:

air alone, air and water combined,

or with the addition of drilling foam
and polymers

to further enhance cutting removal.

First, air alone.

Please note that quality of the cuttings.

They are very clean representative samples
of the formation.

Water is added to enhance the air's
ability to remove the cuttings.

Utilizing the supply truck's reservers and
a direct circulation system,

water is pumped, by the injection pump,

from the truck down the hole
through the drill strength,

and up the annular space between the
string and the bore hole,

removing cuttings out of the hole and
onto the adjacent ground.

Notice how the quality of the cuttings
has changed.

The addition of water has masked the
cuttings,

making it more difficult to identify the
formations and record them accurately.

Drilling foam can be added to the water
which helps fill voids

and suspend the cuttings in the
annular space.

Operators must mix carefully to ensure
foaming action occurs down the bore hole

as opposed to in the mixing tank.

Manufacturer's guidelines and
recommendations

must be followed closely to ensure
optimum performance and safety

when using these products.

The foam fills the annular space, further
enhancing the removal of the cuttings.

Once the foam has dissipated, you can
clearly see the cuttings again.

The drill string sections are threaded
together to enable drilling advancement.

[Worker]: I'm not on the bottom --
on the side.

Good. Good!

[Narrator]: Penetration rates are dictated
by the geology.

For consolidated material,
slow penetration rates

require slow rotation speeds and
lower volumes of flushing medium.

As the material becomes less consolidated,
the rotation speeds

and penetration rates increase as do the
demands on the flushing medium.

The drill string is then tripped out of
the bore hole

to facilitate casing installation.

By utilizing a ribbed stabilizer on the
drill string,

the resulting bore hole is smooth,
straight, and true,

best facilitating the grounding
operations to follow.

The steps involved with the casing
installation may include

initially welding a casing shoe on the
first section of pipe.

This shoe protects the end of the casing
during hole construction

and enables the casing to be properly
seated with the rock.

The shoe must be welded to provide
a water tight seal around the pipe.

Care should be taken to collect spent
welding rod ends.

Additional sections of casing may require
centralizers to be welded onto the casing

to assist in uniform grout placement
as per regulation 903.

A casing elevator is affixed to one end
of the casing

and is hoisted into the air and into
position, safely and securely.

Two technicians are required to safely
install the casing,

as one person operates the hoist while
the other assists by using a rope sling.

Additional sections are welded
or threaded together

as the casing installation occurs.

Grouting occurs to fill the annular space
between the bore hole and casing

as per best management practices
and regulation 903.