Page 25 - Air and Gas Drilling Manual

1-2 Air and Gas Drilling Manual
Air and gas drilling operations have in the past been a small segment of
industrial drilling. In water well drilling operations and environmental monitoring
well drilling operations, fresh water and fresh water drilling muds have been the
drilling fluid of choice. The drilling of deep oil and gas wells where bottomhole
pore pressures can be very large, water based and oil based weighted drilling muds
have been the circulation fluids of choice. Only in the mining industry has drilling
with compressed air been a standard operation competitive with drilling muds. In
the mining industry, the drilling of shallow test boreholes with compressed air
began shortly after portable air compressors became available.
Pneumatic conveying represents the first use of moving air to transport entrained
solids in the flowing stream of air. This air stream was created by steam powered
fans that were the direct outgrowth of the industrial revolution of the early sixteenth
century. Pneumatic conveying was accomplished on an industrial scale by the late
1860’s [1]. The need for higher pressure flows of air and other gases led to the first
reliable industrial air compressors (stationary) in the late 1870’s [2]. Again, these
early compressors were steam powered. After the development of the internal
combustion engines, portable reciprocating and rotary compressors were possible.
These portable compressors were first utilized in the late 1880’s by an innovative
mining industry to drill in mine pneumatic percussion boreholes and shaft pilot
boreholes [2].
After their development, portable compressor technology revolutionized many
industries.
1.1 Rotary Drilling
Rotary drilling is a method used to drill deep boreholes in rock formations of
the earth’s crust. This method is comparatively new, having been first developed by
a French civil engineer, Rudolf Leschot, in 1863 [3]. The method was initially used
to drill water wells using fresh water as the circulation fluid. Today this method is
the only rock drilling technique used to drill deep boreholes (greater than 3,000 ft).
It is not known when air compressors were first used for the drilling of water wells,
but it is known that deep petroleum and natural gas wells were drilled utilizing
portable air compressors in the 1920’s [4]. Pipeline gas was used to drill a natural
gas well in Texas in 1935 using reverse circulation techniques [5].
Today rotary drilling is used to drill a variety of boreholes. Most water wells
and environmental monitoring wells drilled into bedrock are constructed using rotary
drilling. In the mining industry rotary drilling is used to drill ore body test
boreholes and pilot boreholes for guiding larger shaft borings. Rotary drilling
techniques are used to drill boreholes for water, oil, gas, and other fluid pipelines
that need to pass under rivers, highways, and other natural and man-made
obstructions. Most recently, rotary drilling is being used to drill boreholes for fiber
optics and other telecommunication lines in obstacle ridden areas such as cites and
industrial sites. The most sophisticated application for rotary drilling is the drilling
of deep boreholes for the recovery of natural resources such as crude oil, natural gas,
and geothermal steam and water. Drilling boreholes for fluid resource recovery
requires boreholes drilled to depths of 3,000 ft to as much as 20,000 ft.
Rotary drilling is highly versatile. The rotary drilling applications given above
require the drilling of igneous, metamorphic, and sedimentary rock. However, the