Drilling Equipment –
What Goes on the Rigs
Huge quantities of money are spent on the equipment that goes on drilling
rigs. These various types of equipment come as part of the drilling package
offered by vendors or can be procured piecemeal. This article aims to
enumerate the various types of equipment used in drilling and their purposes.
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Drilling
Equipment
Feature
rilling for oil or gas, whether on land or sea,
has a number of common features. A cutting tool, at the end of a drill “string” of pipe
sections screwed one after another, is lowered into a hole, and turned by a rotary table driven
by a powerful engine at around 120 rpm. As the
drilling bit chews into the rock, great heat would be
generated, but this is kept under control by injecting
drilling mud - a special chemical fluid - down the
bottom of the hole at high pressure. The drilling mud,
besides keeping the drill cool, also coats the sides of
the hole and carries the spoil from the drilling bit up
to the surface. The formulation of the mud can be
altered to suit the conditions, and can actually be
used to control any upward pressures that might be
met with in the rock formation.
As the drill advances through the rock, the drill
string is made ever longer with the addition of
more drill pipe sections, and the hole is reinforced
with cylindrical sections of steel casing which prevent the sides from collapsing, with liquid cement
being injected between the casing and the wall of
the well. Drilling will continue using a smaller bit
that fits through the casing. Occasionally, the drill
bit will have to be renewed, which means that
perhaps several miles of drill string have to be
hauled up to the surface again by the rig’s drawworks It may also be replaced with special equipment that can move the hole outwards from the
vertical in any direction.
Once the drill reaches oil or gas-bearing strata,
there is a risk that the pressure at these depths might
force oil or gas up the hole, in what is known as a
“kick”, that could cause damage on the surface, or
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even vent into the air or sea, depending where the
well is situated. While the pressures are carefully
monitored and compensated by increasing the weight
of mud in the well, a heavy structure known as a
blow-out preventer or BOP is installed under the rig,
on the sea bottom in the case of an offshore well.
Powerful hydraulic rams can be activated to close off
the well, shearing the pipe and keeping the rig and
the environment safe.
With an offshore well, all this activity has to be
undertaken aboard a floating structure, if the depth
of water is too great for a jack-up rig, and a ship or a
semi-submersible drilling rig will be used. The craft
will either be anchored, or in the case of very deep
operations, kept over the well by dynamic positioning equipment. Special equipment known as a swell
compensator will be employed to ensure that the
drill string is not harmed by the movement of a
floating craft, while the drilling operations depend
entirely on the activities of supply ships to bring out
more drilling pipe, cement, mud and all the other
supplies it needs.
Drilling Equipment refers to the components and
ingredients that are used for the purpose of Drilling
oil. It is the job of geologists to locate oil with the help
of necessary equipment that are used in an oil trap.
The task of the geologists is to locate a drilling resource such as the right kind of rock, entrapment or
reservoir rock.
Drilling equipment encompasses a variety of
equipment. The major parts of the equipment for
drilling are the following: crown and crown block
situated at the apex of the rig, traveling block,
draw works, sand pipe, engine, fuel or water
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tanks, swivel, rotary hose, turn table, pipe rack,
conductor pipe, bore hole, bit, drill pipe, mud pit
and mud pump. Drilling parts take into consideration all of the above components. Drilling parts
need to be moved to the locations in trucks which
are specially provided for the purpose. The drill
job is done with the help of a rig that is levelled
over the main boring hole.
The drilling equipment comprises of the mast or
derrick that is hauled over the sub structure and
other equipment such as the engines, pumps, and the
hoisting and rotating Equipment that are aligned
together and connected. Drilling constituents like
the drill collars and drill pipe are stretched out on the
racks. The parts of the rig are laid out for the people
to hoist them up when they are required. The components are connected to the drill bit or are attached to
the string for drilling purposes.
Once a drilling oil strike is chanced upon, the
location is marked out by the GPS coordinates on
land or on water (by marker buoys). Equipment is
also used for filling up the tanks with additives.
The drilling mud uses parts for storing on location for usage. The drilling mud which is also
known as fluids are some of the components of
the oil rig and these are used in the rig operations.
They are inspected by the drilling inspectors who
are provided with developed parts. The drilling
parts perform the function with maximum capacity and aid in the construction of a drill.
Equipment when used in the right manner must
depend on the selection of the site and this is something that is generally based on geological evidence
and it indicates the possible accumulation of petroleum gas. The equipment of rigs is provided by the
drilling company that sees to the fact that the equipment is well functional as well as effective. The
drilling of oil requires a charter that has to be granted
from the owner of the land man before the operations
take place.
Oil drilling is a procedure that requires expert
usage of the equipment by the members of the crew.
The crew drills a hole from the starter and drills a hole
from the depth that is preset for drilling. The drilling
of oil with the help of oil equipment that is a process
involves a number of steps. Some of them are:
• the drilling bit is placed in the hole along with the
collar and drilling pipe
• the turn table and the kelly are attached for
drilling with the equipment
• the oil equipment helps circulate the mud through
the pipe and out of the bit for floating the rock
cuttings outside the hole
• new sections or joints in drilling are added in the
pipes as the hole gets deeper
• the pipe is removed or tripped out along with the
other equipment like the bit and the collar once
the preset depth is attained anywhere from several hundred to a few thousand feet
The oil parts must operate and cement the casing
when the pre fixed depth is reached. The drilling gear
must be placed on the casing pipe sections into the
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hole for preventing the Equipment from collapsing
on itself. The exterior of the casing pipe has spacers
for focusing on the hole. The casing crew inserts
the equipment like the casing pipe in the hole. The
casing pipe is pumped down by the cement crew
with the help of a top plug, cement slurry, and
drill mud. Pressure from the drilling mud causes
the cement slurry to move through the casing to
fill in the space between the outside of the hole.
The drilling equipment allows the cement to
harden and once it is done, it is tested for various
kinds of properties such as alignment, rigidity
and the right kind of seal. The oil drill is prepared
by first determining the site which must be then
surveyed for checking out the boundaries for
drilling. After the settlement of the legal formalities, the crew moves ahead with the equipment
for preparing the land. The land is cleared and
leveled for the process to take place. Since water
is an important constituent, there must be a water
body or source of water in the vicinity. If there is
none, a well is drilled.
A reserve pit is dug for the oil drilling purposes
for the disposal of the rock cuttings and drilling of
mud for bordering it with plastic for ensuring the
protection of the environment. If the area in question is ecologically sensitive, like a wilderness
space or marsh, make sure to dispose of the rock
cuttings away from the site in a truck, instead of
placing them in a pit.
After preparing the land, several holes need to
be dug for making room for the rig as well as the
main hole. A cellar, which is also rectangular in
shape, is dug around the location of the real drill
hole. The cellar is actually a place of work for the
workers as well as is made for housing the drills
and accessories. Once the main hole is drilled, it is
lined with a conductor pipe that is large in diameter for oil extraction.
Selected Equipment and Purposes
Drilling
Equipment
Feature
Hoisting Equipment
The hoisting equipment on a rotary rig consists
of the tools used to raise and lower whatever
other equipment may go into or come out of the
well. The most visible part of the hoisting equip-
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ment is the derrick, the tall tower-like structure
that extends vertically from the well hole. This
structure serves as a support for the cables (drilling lines) and pulleys (draw works) that serve to
lower or raise the equipment in the well. For
instance, in rotary drilling, the wells are dug with
long strings of pipe (drillpipe) extending from the
surface down to the drill bit. If a drill bit needs to
be changed, either due to wear and tear or a
change in the subsurface rock, the whole string of
pipe must be raised to the surface. In deep wells,
the combined weight of the drillpipe, drill bit,
and drill collars (thicker drillpipe located just
above the bit) may be in excess of thousands of
pounds. The hoisting equipment is used to raise
all of this equipment to the surface so that the drill
bit may be replaced, at which point the entire
chain of drillpipe is lowered back into the well.
Working on an Onshore Drilling Rig
Source: Anadarko Petroleum Corporation
The height of a rigs derrick can often be a clue as
to the depth of the well being dug. Drillpipe traditionally comes in 30ft sections, which are joined
together as the well is dug deeper and deeper. This
means that even if a well is 20,000 feet deep, the
drill string must still be taken out in 30 foot sections. However, if the derrick is tall enough, multiple joints of drillpipe may be removed at once,
speeding up the process a great deal.
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drill through hard rock. The number and nature
of the drill collars on any particular rotary rig can
be altered depending on the down hole conditions experienced while drilling.
Positioning the Hoisting Equipment
Source: Anadarko Petroleum Corporation
Drilling
Equipment
Feature
Rotating Equipment
The rotating equipment on a rotary drilling rig
consists of the components that actually serve to
rotate the drill bit, which in turn digs the hole deeper
and deeper into the ground. The rotating equipment
consists of a number of different parts, all of which
contribute to transferring power from the prime
mover to the drill bit itself. The prime mover supplies
power to the rotary, which is the device that turns the
drillpipe, which in turn is attached to the drill bit. A
component called the swivel, which is attached to the
hoisting equipment, carries the entire weight of the
drillstring, but allows it to rotate freely.
The drillpipe (which, when joined together,
forms the drillstring) consists of 30ft sections of
heavy steel pipe. The pipes are threaded so that
they can interlock together. Drillpipe is manufactured to meet specifications laid out by the American Petroleum Institute (API), which allows for a
certain degree of homogeneity for drillpipes across
the industry. The drillpipe is a very heavy, strong
pipe, but can be quite flexible when used in slant
or horizontal drilling applications.
Below the drillpipe are drill collars, which are
heavier, thicker, and stronger than normal
drillpipe. The drill collars help to add weight to
the drillstring, right above the bit, to ensure there
is enough downward pressure to allow the bit to
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Drill Bits
The drill bit is located at the bottom end of the
drillstring, and is responsible for actually making
contact with the subsurface layers, and drilling
through them. The drill bit is responsible for breaking up and dislodging rock, sediment, and anything
else that may be encountered while drilling. The drill
bit is hollow and has jets to allow for the expulsion of
the drilling fluid, or “mud”, at high velocity and high
pressure to help clean the bit and, for softer formations, help to break apart the rock. A tricone bit
comprises three conical rollers with teeth made of a
hard material, such as tungsten carbide. The teeth
break rock by crushing as the rollers move around
the bottom of the borehole. There are dozens of
different drill bit types, each designed for different
subsurface drilling conditions. Different rock layers
experienced during drilling may require the use of
different drill bits to achieve maximum drilling efficiency. It can be a long process to change bits, due to
the fact that the whole drill string must be removed;
but using the correct drill bit, or replacing a worn bit,
can save a great deal of time during drilling. Drill bits
are chosen given the underground formations expected to be encountered, the type of drilling used,
whether or not directional drilling is needed, the
expected temperatures underneath the Earth, and
whether or not cores (for logging purposes) are required. There are four main types of drill bits, each
suited for particular conditions.
Diamond Studded Drill Bits
Source: Sandia National Laboratory (left), DOE - National
Energy Technology Laboratory
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• Steel Tooth Rotary Bits are the most basic type of
drill bit used today.
• Insert Bits are steel tooth bits with tungsten carbide inserts.
• Polycrystalline Diamond Compact Bits have
polycrystalline diamond inserts attached to the
carbide inserts found in Insert Bits.
• Diamond Bits have industrial diamonds implanted in them, to drill through extremely hard
rock formations. Diamond bits are forty to fifty
times harder than traditional steel bits, and can
thus be used to drill through extremely hard rock
without dulling overly quickly.
PDC bit for well drilling
Multiple Tricone (carbide) insert Bits
Typical tri-cone rock bit
Tricone (carbide) insert Bit
Tricone rock bit (medium worn-out)
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Tricone rock Bit
drill hole above the drill bit, and the mill bit is
designed to mill away metal scraps or objects
found in the well. The drill bit, in addition to
being very useful, is also very expensive. It is thus
up to the drilling engineer to ensure that the
correct bit is used at the correct time, to allow for
maximum drilling efficiency, with minimum wear
and tear on the valuable bit.
In addition to these main types of drill bits,
hybrid bits, combining the features of various
types of bits, can be used. If core samples are
required for logging purposes, core bits are designed to drill and obtain these samples. There
are a great number of different designs for drill
bits, including tricone roller bits, button bits, tapered bits, fishtail bits, and mill bits. Each of these
bits has specifically designed drilling traits. The
fishtail bit, for instance, is designed to enlarge the
Drilling
Equipment
Feature
Lowering the Bit and Drill Collar into the Well Hole
Source: NGSA
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Blowout Preventer
A blowout preventer is a large, specialized valve
or similar mechanical device, usually installed
redundantly in stacks, used to seal, control and
monitor oil and gas wells. Blowout preventers
were developed to cope with extreme erratic pressures and uncontrolled flow (formation kick) emanating from a well reservoir during drilling. Kicks
can lead to a potentially catastrophic event known
as a blowout. In addition to controlling the
downhole (occurring in the drilled hole) pressure
and the flow of oil and gas, blowout preventers
are intended to prevent tubing (e.g. drill pipe and
well casing), tools and drilling fluid from being
blown out of the wellbore (also known as bore
hole, the hole leading to the reservoir) when a
blowout threatens. Blowout preventers are critical to the safety of crew, rig (the equipment system used to drill a wellbore) and environment,
and to the monitoring and maintenance of well
integrity; thus blowout preventers are intended
to be fail-safe devices.
The abbreviated term preventer, usually prefaced by a type (e.g. ram preventer), is used to
refer to a single blowout preventer unit. A blowout preventer may also simply be referred to by
its type (e.g. ram).
The terms blowout preventer, blowout preventer
stack and blowout preventer system are commonly used interchangeably and in a general
manner to describe an assembly of several stacked
blowout preventers of varying type and function,
as well as auxiliary components. A typical subsea
deepwater blowout preventer system includes
components such as electrical and hydraulic lines,
control pods, hydraulic accumulators, test valve,
kill and choke lines and valves, riser joint, hydraulic connectors, and a support frame.
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Two categories of blowout preventer are most
prevalent: ram and annular. BOP stacks frequently utilize both types, typically with at
least one annular BOP stacked above several
ram BOPs.
Blowout preventers are used at land and offshore rigs, and subsea. Land and subsea BOPs
are secured to the top of the wellbore, known as
the wellhead. BOPs on offshore rigs are mounted
below the rig deck. Subsea BOPs are connected
to the offshore rig above by a drilling riser that
provides a continuous pathway for the drill
string and fluids emanating from the wellbore.
In effect, a riser extends the wellbore to the rig.
Circulating System
Another component of rotary drilling consists
of the circulating system. There are a number of
main objectives of this system, including cooling
and lubricating the drill bit, controlling well pressure, removing debris and cuttings, and coating
the walls of the well with a mud type-cake. The
circulating system consists of drilling fluid, which
is circulated down through the well hole throughout the drilling process.
Typically, liquid drilling fluids are used. The
most common liquid drilling fluid, known as
‘mud’, may contain clay, chemicals, weighting
materials, water, oil, or gases. ‘Air drilling’ is the
practice of using gasses as the drilling fluid,
rather than a liquid. Gases used include natural
gas, air, or engine exhaust. Air drilling can significantly cut down on drilling time, as well as
drilling fluid costs. The drilling fluid, much like
the bit, is custom designed and chosen depending on what type of subsurface conditions are
expected or experienced. For example, if drilling
is occurring through underground salt formations, freshwater would not be used, as this
would risk dissolving the subsurface salt. Similarly, if drilling near sources of fresh water, salt
water would not be used for fear of contaminating the fresh water.
The drilling fluid chosen must have a number
of properties to allow it to accomplish its tasks. It
must be light and thin enough to circulate through
the drill bit, cooling the bit as it drills as well as
lubricating the moving parts. The fluid must be
heavy enough to carry drill cuttings away from
the bit and back to the surface, as well as control
upward pressure that may be experienced in the
well to prevent blowouts. The drilling fluid engineer ensures that the weight of the drilling fluid
is greater than the upward pressure of escaping
gas that may be encountered while drilling. In
addition, the drilling fluid must be thick enough
to coat the wellbore with a cake, which serves to
temporarily seal the walls of the well until casing
can be installed.
The circulating system consists of a starting
point, the mud pit, where the drilling fluid ingredients are stored. Mixing takes place at the mud
mixing hopper, from which the fluid is forced
through pumps up to the swivel and down all the
way through the drill pipe, emerging through the
drill bit itself. From there, the drilling fluid circulates through the bit, picking up debris and drill
cuttings, to be circulated back up the well,
traveling between the drill string and the walls of
the well (also called the ‘annular space’). Once
reaching the surface, the drilling fluid is filtered
to recover the reusable fluid.
In addition to the fluid itself regulating
downhole pressures encountered while drilling,
a device known as the ‘blowout preventer’ is
situated on the well casing below the deck of the
rig. A blowout can occur when uncontrolled underground oil or gas pressure exerts more upward pressure than the drilling fluid itself can
offset. The blowout preventer can consist of hydraulically powered devices that can seal off the
well quickly and completely, preventing any potential for a well blowout should extreme
downhole pressures be encountered. Pressure
release systems are also installed to relieve the
great pressure that can be experienced in a blowout situation.
References
BIMCO
NaturalGas.org
Wikipedia
Flowtech Energy
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