3. The Petroleum Perforation
Drilling is an activity that demands
time and financial resources. For this
reason, a drilling rig is only installed and
begins to drill when geologists and
geophysicists have agreed on the most
suitable location for the search for
hydrocarbons in the subsoil.
The tankers were not the first to drill
deep wells: 2,000 years ago the Chinese
did it to find brine, with which they
obtained salt. To achieve their purposes,
they had a team consisting of a wooden
structure, from which a sharp and heavy
tool was suspended by cable. The
intermittent percussion on the ground
was piercing successive strata of the
subsoil until arriving at the objective.
This ingenious system allowed drilling
up to more than 900 meters deep,
although it took years to complete the
work.
In the first years of the oil industry, the same
principles were used, from percussion drilling.
Although still in certain circumstances and mainly
in the United States, this technique is still used
(much improved compared to the last century) it
was universally replaced by the rotary drilling
method.
The tower or drill mast forms the most
prominent part of the equipment (usually 40
meters high), and is composed of four large steel
columns of rectangular shape, joined laterally.
At the top of the tower or mast, suspended
from cables, the injection head is located,
connected to the bore bar. The injection head
allows a liquid (drilling mud) to pass through and
at the same time allows the drill rod to rotate
freely in the subsoil. The probing bar -united in
sections of 9 meters- passes through a master
bushing located on the rotary table placed on the
floor of the mast or tower. Diesel or electric
motors rotate the rotary table and the entire
drilling column, at the end of which is the drilling
bit.
4.
5. Underwater Drilling Platform
But the drilling of an oil well is not just a
high-precision engineering work: it is a
work of permanent attention and tension
for the men who make up the team. The
sides of the well can be hollow and the
injection liquid can be lost through the
cavities; the trephine can be imprisoned by
salt. To avoid these risks periodically, the
drilling string is removed, and an
intubation pipe that will support the walls
of the well is installed in its place.
Between this pipe and the walls of the
well a slurry of cement is introduced, which
once set will permanently sustain the
entire complex. The drilling string then
passes through the installed pipe, which
will continue to operate with a smaller
diameter.
At greater depth, a second section of
tubing with a smaller diameter will be
introduced than the first and, probably, later,
also a third section that will pass through the
second. Thus, when the well is reaching its
final depth, the diameter of the trepan may
not exceed 10 centimeters, although the
drilling has begun with a diameter of 50.
Throughout this process are frequent
changes of trepan, maneuver that requires
another previous: withdrawal from the polling
bar.
The driller must also be careful, to avoid
that the tool is imprisoned in the bottom of
the well or that the string deviates from the
vertical, maneuvering permanently with the
rotation speed of the trepan and the weight of
the drill string to achieve the correct balance
of the entire operation.
Finally, all the drilling equipment that
almost always operates in the open,
subjected to inclement weather, must be
prepared to face, control and overcome the
consequences of a gas leak, which can be
devastating for the team and for the men who
work. with the. Although the oil industry has
developed sophisticated safety techniques
for the prevention of this type of accident,
none is useful when the people in charge, by
distraction or forgetfulness, stop paying
attention to them. And in the well, which is
one of the most difficult works of engineering
on Earth, almost always there are plenty of
reasons for distraction.
Finally, after the drilling program is
finished, it is likely that no oil or natural gas
will be found, or that the volume of
hydrocarbons verified does not justify the
commercial development of the well. All the
money and the efforts invested by the
company will have been useless and the
drillers will try again in another location