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Anatomy of an Oil
Well
From
FOSSIL OIL & GAS, L.L.C
LAYMAN'S GUIDE
Preparation for Drilling
A
lot of people think that drilling for oil amounts to
finding a spot where "bubbling' crude" oozes from
the soil a'la Jed Clampet -- drilling a hole and
waiting for the black sludge to come squirting to
the surface like Old Faithful. It's not quite that
way. Drilling for oil today is a complex, scientific
process of coaxing oil that's deeply embedded in
sandstone or limestone, not like a gusher, but more
like a leaking faucet -- drop by drop.
Fossil Oil & Gas' engineers and workers use a
combination of sciences including seismology,
geology and physics. Once geologists have determined
that an area may contain oil, dirt work begins at
the drilling site to prepare a suitable location for
the drilling rig. A drilling rig, complete with a
90-foot derrick (mast) is erected at the site.
 Once
the engines are assembled on the site and the rig is
up, drilling for surface casing begins. The surface
casing is usually set below any fresh water
formations, often approximately 300 to 400 feet
deep. The casing itself comes in 40-foot sections,
which are threaded at both ends. Workers, or
"roughnecks" attach the sections with a "collar"
which also is threaded. Chains are used to spin the
pipe into the threaded collar. The roughnecks then
tighten the collar with a large pipe wrench. Once
the surface casing has been run into the hole, a
special cement is pumped in. The cement seals the
area between the surface casing and the side of the
hole protecting all fresh water formations from
contamination as the well is drilled deeper. Then,
drilling commences once again.
Drilling, Testing & Completion
The drill bit and 30-foot sections of drill pipe are
used to drill deeper toward the potentially
oil-bearing formation. A liquid consisting of fresh
water and bentonite is mixed (on the fly) to a
gelatin-like consistency and is pumped into the hole
to carry the drill cuttings to the surface. This
liquid is called "drilling mud."
Once the hole reaches the desired depth, , logging
begins. Logging is the process of determining which
of the formations between the surface and the bottom
of the well contain oil and gas and which formations
contain merely water. An electrical cable and a
"logging tool" are lowered into the hole, and the
tool sends electrical charges into the formation.
Logging contractor employees prepare to lower the
20-foot logging tool into the hole. 5000' of drill
pipe is standing beside them. The tool then sends
this geological information to the "logging" truck
where a computer processes the information. The
information which can be derived from logging
includes rock type, porosity, and resistivity (oil
resists electricity; water conducts it).
Once this information is gathered and studied, a
decision is made to either plug or complete the
well. This is called the "casing point decision."
Once the decision to complete the well has been
reached, enough casing is lowered into the hole to
reach the bottom (often over 5000 feet). A worker,
called a "stabber" makes sure the casing is
"stabbed" straight into the joint of each piece of
casing. Power tongs screw the pipe together until it
reaches the proper
torque. Cement is then pumped into the hole through
the casing. When it hardens, the cement forms a seal
between the outside of the casing and the wall of
the hole itself. The last joint or section of casing
pipe is then cut off at ground level.
The
Final Touch
The rig and derrick are removed, and a service rig
moves in to complete the well. A perforating gun
blows
 holes
through the casing and cement into the rock using
shaped explosive charges. The perforating gun blows
a hole about every three inches down the hole with a
computer telling the gun when to shoot. These holes
or "perforations" then allow the oil to seep into
the casing. However, another step must be taken to
improve the quantity of oil seeping into the casing.
This next step involves "loosening" the oil that is
trapped in the porous rock using a process called "fracing"
(pronounced fracking). This is accomplished by
pumping water at extremely high pressure into the
hole until a crack develops in the rock formation.
Water and sand are then pumped into the crack, which
often extends as far as 1200 feet. Once pumping is
ceased, the sand holds the cracks open and is a
great deal more porous than the rock which contains
the oil. Once all this is accomplished, the oil
begins to escape the fractured rock and flows into
the casing. The service rig is then utilized to run
another string of pipe into the well (inside the
casing). This string
of pipe is called the "tubing." A pump is also
installed in the bottom of the well. A "roustabout"
crew then assembles the pumping unit and installs
the pipelines which transport the oil and natural
gas which have been pumped out of the formation to a
separation facility. The gas and oil are separated.
The gas flows into a gas pipeline, and the oil is
stored in tanks. The oil is then trucked or shipped
via pipeline to a refinery.
NOTE: The steps for
producing oil and gas as outlined above are typical
. Producing oil and gas in different geographic
areas and for different productive formations can be
significantly different.
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