CABLE TOOL METHOD
Cable tool method has its beginnings 4000 years ago in China. it was the earliest drilling method
and has been in continuous use for about 4000 years. The Chinese used tools constructed of
bamboo and well depths of 3000 ft are recorded. However, wells of these depth often took
.generations to complete
Cable tool rigs are sometimes called pounders, percussion, spudder or walking beam rigs. They
operate repeatedly lifting and dropping a heavy string of drilling tools into the boreholes. The drill
bits breaks or crushes consolidate rock into small fragments. When drilling in unconsolidated
.formations, the bit primarily loosens material
Water, either from the formation or added by the driller, mixes the crushed or loosened into a
slurry at the bottom of the borehole. An experienced cable tool driller feels when the accumulated
slurry has reached the point where it is reducing bi penetration to an unacceptably slow level. At
this point the slurry is removed from the borehole by a bailer. Once the slurry is removed, the bit
.is reinserted into the hole and drilling continues
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Often a cable-tool rig drills only one-tenth as fast as a rotary rig in comparable formations
However, the cost of a cable-tool rig is substantially less than a rotary rig. This tends to
compensate for its slower drilling rate. A distinct disadvantage of the cable-tool method is that
when high-pressure oil and gas formations are encountered, there is no fluid in the hole to control
them. The result is frequent blowouts. When a blowout occurs, the oil and gas from the subsurface
formation rush to the surface and flow uncontrolled. A blowout may spray
the oil and gas several hundred feet into the air, and there is always great danger of a fire. Because
of its slow penetration rate and the hazard of blowouts, the cable-tool method is seldom used on
wells deeper than (3000 ft or 900 meters). Even on shallower wells, this method has largely been
.replaced by the rotary method
ROTARY DRILLING METHOD
In Rotary drilling, a bit used to cut the formation is attached to steel pipe called drillpipe. The bit is
lowered to the bottom of the hole. The pipe is rotated form the surface by means of a rotary table
through which is inserted a square or hexagonal piece called a kelly. The Kelly (in the top drive
system the rotary table and Kelly are not exist), connected to the drillpipe at the surface, passes
through the rotary table. The turning action oft the rotary table is applied to the Kelly, which is turn
rotate, the drillpipe and the drilling bit. Routine drilling consists of continuously drilling
increments the length of one joint of pipe, making connections or adding to the drillstring another
single joint of pipe, generally 30 or 45 ft long. This drilling continues until the drill bit must be
changed. Changing the bit is also called making a trip
The idea of rotary drill bit is not new. Archaeological records show that as early as 3000 B.C., the
Egyptians may have been using a similar technique. Leonardo Di Vinci, as early as 1500
developed a design for a rotary drilling mechanism that bears much resemblance to technology
used today. Despite these precursors, rotary drilling did not rise in use or popularity until the early
Although rotary drilling techniques had been patented as early as 1833, most of these early
attempts at rotary drilling consisted of little more than a mule, attached to a drilling device
walking in a circle! It was the success of the effort of captain 'Anthony Lucas' and 'Patillo Higgins
in drilling their 1901 'Spindltop' well in Texas that catapulted rotary drilling to the forefront of
petroleum drilling technology