Page 391 - Air and Gas Drilling Manual

8-74 Air and Gas Drilling Manual
air and injected water to eliminate rock cuttings. Continue this drilling
and cleaning procedure for 15 to 30 minutes or until the air flow (with
injected water) returning to the surface is clean (i.e., shows a fine spray
and white color).
8. With the drill bit directly on bottom, continue flowing air with no
injected water into the drill string. Air should flow to the well at normal
drilling volumetric flow rates until the water and surfactant remaining in
the well are swept to the surface.
9. Continuously blow the hole with air for about 30 minutes to an hour.
10. Begin normal air drilling. After 5 ft to 10 ft have been drilled, the hole
should go to dry dust drilling (although it is sometimes necessary to drill
as much as 60 ft to 90 ft before dry dust appears at the surface). If the
hole does not dust after these steps have been carried out, inject another
surfactant slug into the air flow to the well. If dry dusting cannot be
achieved, unstable foam drilling may be required to complete the air
drilling operation.
Air Lift Procedure
The air lift procedure is as follows:
1. Calculate the lifting capability of the primary and booster compressors on
the drilling location. Run the drill string made up with the appropriate
bottomhole assembly and drill bit to a depth a few hundred feet above
this calculated compressor pressure limit.
2. Start the compressors and force compressed air to the bottom of the drill
string and begin aerating the water column in the annulus and flow this
aerated water column to the surface (removing this portion of the column
from the well).
3. Once this column of water has been removed, shut down the compressors
and lower the drill string a similar distance as defined by the lifting
capability limit determined in No. 1 above. Start up the compressors and
remove this next column of water from the well.
4. Continue lowering the drill string in increments and air lifting the entire
water column from the well.
5. With the drill bit directly on bottom, continue flowing air into the drill
string. Air should flow to the well at normal drilling volumetric flow
rates until the water and surfactant remaining in the well are swept to the
surface.
6. Continuously blow the hole with air for about 30 minutes to an hour.
7. Begin normal air drilling. After 5 ft to 10 ft have been drilled, the hole
should go to dry dust drilling (although it is sometimes necessary to drill
as much as 60 ft to 90 ft before dry dust appears at the surface). If the hole
does not dust after these steps have been carried out, inject another
surfactant slug into the air flow to the well. If dry dusting cannot be
achieved, unstable foam drilling may be required to complete the air
drilling operation.
Slug Procedure
The slug procedure (also known as “rocking the well”) is similar to that given in
the aerated fluid procedure given above. However, in the slug procedure the mud