Preparation for Drilling
A lot of people think that drilling for oil amounts to finding a
spot where "bubblin' 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.
Operating, Incorporated's 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.
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.