Drilling Preliminaries Steps

Drilling Preliminaries
Kartikeya Pandey Prof Anil Kumar
MBA IFM (HOD Power & Infrastructure
500021353 Management)
Submitted by Submitted to

Steps to Drill A Gas/Oil Well
1. Complete or obtain seismic, log,
scouting information or other
data.
2. Lease the land or obtain
concession.
3. Calculate reserves or estimate
from best data available.

Steps to Drill A Gas/Oil Well
4. If reserve estimates show
payout, proceed with
well.
5. Obtain permits from
conservation / national
authority.
6. Prepare drilling and completion
program.

Steps to Drill a Well - cont’d
7. Ask for bids on footage, day work,
or combination from selected
drilling contractors based on
drilling program.
8. If necessary, modify program to fit
selected contractor equipment.
9. Construct road, location/platforms
and other marine equipment
necessary for access to site.

Steps to Drill a Well - cont’d
10. Gather all personnel concerned for
meeting prior to commencing
drilling (pre-spud meeting).
11. If necessary, further modify
program.
12. Drill well.

Introduction
When a suitable
structure, sufficiently large, so as
to give economically viable reserves
of HCs) is discovered for the
presence of HCs by
geological, geochemical &
geophysical methods, a location for
drilling of an exploratory / wild cat
well is decided.

Classification of Wells
Exploratory Well / WildCat
Well:
They are drilled purely for
exploratory purposes i.e. for
gathering information. The well is
drilled to find and produce oil or
gas in an unproven area, or to find
a new reservoir in fields, or to
extend a known reservoir.

Discovery Well:
If the well does discover a new
field, it is called the discovery well
for that field.

Appraisal Well/ Delineation
Well:
After the discovery, the size of the field
must be determined. Field size is
determined by “step out” or
“Delineation” or “Appraisal” well that
are drilled to the sides of the discovery
well.

Developmental Wells:
Wells drilled in the known extent of
the field are called Developmental
Wells.

Infill Wells:
Wells that are drilled in between
producing wells in an established
field to increase the production
rate are called Infill wells.

Production Wells:
They are drilled primarily for
producing oil and gas, once the
producing structure and
characteristics are determined.

The well is created by drilling a hole of
5 – 36 inches (127.0 – 914.4 mm) in
diameter into the earth with a drilling
rig that rotates a drill string with bit
attached.
• The cost of drilling is very great. On
an offshore rig, it may cost $10,000
for each metre drilled.
• A company incurs vast losses for
every “dry hole” drilled.
Drilling A Well

A drilling rig is the machine which
creates holes (usually called
boreholes) in the ground.
Drilling Rig

Drilling rigs can be:
• Small and portable, such as those
used in mineral exploration
drilling, water wells and
environmental investigations.
• Huge, capable of drilling through
thousands of meters of the Earth's
crust.
Drilling Rig

Drilling rigs can be mobile equipment
mounted on trucks, or trailers, or more
permanent land or marine-based
structures (such as oil platforms,
commonly called 'offshore oil rigs).
The term "rig" therefore generally
refers to the complex of equipment
that is used to penetrate the surface of
the Earth's crust.

Primarily in onshore oil & gas
fields, once a well has been
drilled, the drilling rig is moved
off of the well and a service rig ( a
smaller rig) for completions is
placed for well completion.
This frees up the drilling rig to
drill another hole and streamlines
the operation.

In early oil exploration, drilling
rigs were semi-permanent in
nature and the derricks were
often built on site and left in
place after the completion of
the well.

Cable Tool Drilling
Cable Drilling is a pioneer
method and the first oil wells in
the United States were drilled
with cable tools to a depth of
20 mts.

Cable Tool Drilling
An engine , originally a steam
engine, causes a wooden
beam to pivot up & down.
The bit, is made up of solid
steel rod about 4 ft. (1 & 1/3m)
long with a chisel point on it.
Drilling Rig

Steam
Engine
Walking
Beam
Derrick
Drawworks
Pulley
Bit
Drill collar
Drill ing Line

Cable Tool Drilling ( Cont…..)
As the walking beam pivots, it
causes the bit to rise and fall.
The bit pounds the well down
by pulverizing the rock.
Drilling Rig

After drilling 3 - 8 ft., (1 – 2 ½ m),
the bottom of the well becomes
clogged with rock chips.
The bit is raised and a bailer is
lowered into the well to remove
the rock chips and water.
Drilling Rig

After the bailer is raised and
emptied, the bit is lowered into
the well to pound deeper.
Drilling Rig

Heavy casing ( large diameter
pipe) is run down the well to
keep water from filling the well
and to prevent the sides from
caving in.
Drilling Rig

Cable tool drilling is very slow –
25ft. ( 7 ½ m) per day (average)
and 60 ft. (20m) being very
good.
Drilling Rig

Rotary Drilling
Today, almost all well are drilled
with rotary drilling rigs.
The rotary drilling rig rotates a
long length of steel pipe with a
bit on the end of it to cut a hole
called the well bore.
Drilling Rig

Rotary Drilling
The rotary rig consists of four major
systems.
(1) Power System : Diesel Engine
(2) Hoisting System : Derrick / Mast,
Draw work
(3) Rotating System : Swivel, Kelly,
Rotary table, Drill string, Drill Pipe,
Drill Collar, Bit etc.
(4) Circulating system: Mud Tanks

Derrick
Crown Block
Shale Shaker
Mud tank
Swivel
Drill Line
BOP
Mud Pump
Motor/ Power Source
Drill Bit
Kelly
Rotary Table

Crown Block:
 A fixed, steel frame with steel
wheels on a horizontal shaft. It is
located at the top of a derrick or
Mast.
 Is an assembly of pulleys
mounted on beams at the top of
derrick

Derrick:
The derrick or Mast is the tower directly
above the well that supports the crown
block at the top & provides support for
the drill pipe to be stacked vertically as
it is pulled from the well.
It is generally 40m in height strong
enough to hold the weight of the drill as
it goes deeper & deeper into the rock.
The derrick can support a weight of
about 50 tonnes or more.

Kelly :
The kelly is a square rod
attached to swivel.
The kelly turns all the pipe
below it to drill the hole.
To the lower end of the kelly, a
10 m pipe is screwed in.

DrilPipe:
The drillpipe (which, when joined
together, forms the drillstring)
consists of 30ft. (10m) sections
of heavy steel pipe. The pipes
are threaded so that they can
interlock together.
As the drill goes deeper, a new
pipe is added to the end of the
first pipe and so on.

Swivel :
The swivel allows the kelly to
rotate freely.

Rotary Table:
The kelly along with the pipe &
drilling bit is rotated by a rotor
known as “Rotary Table”.
It is a circular table in the derrick
floor that is turned clockwise by
the prime movers. If it were
turned in the opposite direction,
the drillpipe would unscrew.

Drill stem:
3 main components are Kelly,
Drillstring & the Bit.
Drill string:
It is made up of steel pipes called drill
pipes, drill collars (below the drill pipes
are thicker – walled, heavier, stronger pipes
to put weight on the bottom of the drills
string to drill straight down and prevent the
drill pipe from kinking & breaking) and bit
in the well.

Drill string:
It is made up of steel pipes called drill
pipes, drill collars (below the drill pipes
are thicker – walled, heavier, stronger pipes
to put weight on the bottom of the drills
string to drill straight down and prevent the
drill pipe from kinking & breaking) and bit
in the well.

Drill Bit :
It is located at the bottom end of
the drill string. The drill bit is
responsible for breaking up and
dislodging rock, sediment, and
anything else that may be
encountered while drilling. There
are dozens of different drill bit
types, each designed for different
subsurface drilling conditions:

1.Steel Tooth Rotary Bits are
the most basic type of drill
bit used today.

2. Insert Bits are steel tooth
bits with tungsten carbide
inserts.

Disadvantages of Insert Bit
• Inserts dig deeply into formation.
Cones can hit the formation and
transmit shock loads to bearings and
damage bearings
• Abrasive mud containing sands can
erode cutters base and let them fall
in the well
• Much more expensive
• Can not drill soft to soft-medium hard
formations as fast as steel-tooth bits

3. Polycrystalline Diamond
Compact Bits have
polycrystalline diamond
inserts attached to the
carbide inserts found in
Insert Bits.

4. 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.

Drilling Mud:
When the drilling goes on , a special
type of drilling fluid known as mud is
pumped down by a hose through the
drilling pipe to keep the bit cool.
(The mud flows just like ink flows out of a pen)
A viscous mixture of clay (usually
bentonite) and additives with either
water or oil or an emulsion of water
with droplets of oil or a synthetic
organic fluid.

Drilling Mud ( Cont…..)
The mud squirts out of the drilling bit
and flows back through the annular
space between the outer side of the
pipe and the drilled hole carrying with
it chips of rocks that are cut.

Geologists work day and night to
record the sequence in which the
different types of rocks come out.
After studying the rocks, the
geologists prepare a map showing the
vertical distribution of rocks
underground.

From this map, it is possible to find
out :
(1) The type of rock
(2) The depths at which different rock
types occur
(3) The thickness of the bed of each
rock type.
The geologists also note if the rocks
give any sign of oil.

3) the mixture of drilling
mud and drill cuttings are
circulated up the annulusscreens
5) the drill cuttings are
removed, and form a cuttings
pile. This can be hauled off and
4) the mixture is
circulated across
screens at surface
1) Clean drilling mud is
taken from the steel mud
tanks and pumped down the
inside of the drill pipe.
2) the mud is circulated through
the drill bit into the
annulus, lifting the cuttings
removed by the drill bit.
6) Clean mud
falls through
the screens and
is returned to
the pits
The Drilling Mud Cycle
mud pump

The drilling mud is circulated
on a rotary drilling rig to :
1.Cool & lubricate the drillstem.
2. remove cuttings from the
hole.
3. control subsurface
pressures.
4. Seal permeable formations.

Safety System
Various safety devices are
used at the wellhead to cope
with dangerous situations
that may occur during a
drilling operations:

Safety System
Reservoirs penetrated by the
drill may contain pressures
higher than the mud weight can
control and the well may
show a tendency to erupt and
blowout.

Safety System
 When oil is struck, the oil gushes out.
 Sometimes the oil gushes out with
such tremendous force that it becomes
dangerous.
 The “Blow – Out” can kill men and
damage the oil rig.
 To reduce the risk of oil gushing
out, there is a strong cap in every
well.
The cap is used as a “BLOW OUT
PREVENTER” or “BOP”.

WELL COMPLETION
Once a natural gas or oil is drilled , and it
has been verified that commercially viable
quantities of crudes are present, for
extraction, the well must be “completed”.
Completion is done to allow for the flow of
crude out of the formation and up to the
surface.

WELL COMPLETION ( Cont…..)
Completion includes strengthening
the well hole with casing, evaluating
the P & T of the formation and then
installing the proper equipment to
ensure an efficient flow of the crudes.

WELL COMPLETION ( Cont…..)
Completing a well consists of :
 Installing the well casing
 Completing the well
 Installing the wellhead
 Installing lifting equipment
 Treating the formation.

Well Casing
Installing well casing is an important
part of the drilling and completion
process.
Well casing consists of a series of
metal tubes installed in the freshly
drilled hole.

Objectives of Casing:
1. Supports the walls of the wells.
2. Prevents caving tendencies of
unconsolidated formation.
3. Prevents water from entering the
oil and gas yielding strata from
overlying or underlying formations.

Gas & oil must be confined within the
well casing so that they may not
escape into overlying / underlying
formation.

If the hole is uncased, oil and gas
could escape through the well into a
permeable horizon having a lower
pressure and thus, can be dissipated
through them so that desired
recovery can never be effected.

In oil well drilling, the cost of casing is
usually the greatest single item of
expense and selection of pipe weight ,
size and planning and design of
casing installation etc. are amongst
the most important problems
encountered in well drilling.
WHY???

 The casing required to be lowered in
the well should be effectively serve
the purpose.
 It must be of sufficient strength,
adequate to withstand the stresses
to which it is subjected in the well.
 It should be water tight and it
should be made of material that
resists corrosion or be protected
against corrosion (particularly when it
is in contact with saline ground water)

 The material of which the casing is
made should be hard & tough and
rigid enough to resist abrasion and
distortion by contact with the rock
walls of the well or drilling tools.

TYPES OF CASING
Casing types involve the
character of the material from
which the tubes are made, the
method of their manufacture, the
design of the joints and especially
the method of connecting one
individual section to another.

TYPES OF CASING
 In recent years, economy and safety of
operation at increased depths have
necessitated still further changes and
improvements in the casing designs.
 Resulted in the use of alloy steels having
tensile strength of 80.000 lbs / inch2 or
more with further changes in thread and
coupling designs.
 There are four grades of seamless alloy
steel casing in use.

In most wells, the diameter of the well
hole decreases the deeper it is drilled,
leading to a type of conical shape that
must be taken into account when
installing casing.

A well commonly has 3 or more
concentric casing string.
Shallow wells can have 2 or just 1
casing string.
The largest diam. & shortest length
string is on the outside.
The smallest diam. & longest length
string is on the inside.
The outside string is cemented first
and the inside string last.

There are five different types of well
casing:
• Conductor Casing
• Surface Casing
• Intermediate Casing
• Liner String
• Production Casing

Conductor Casing
• Conductor casing is installed first,
usually prior to the arrival of the
drilling rig.
• The hole for conductor casing is
often drilled with a small auger drill,
mounted on the back of a truck.

Conductor Casing
• Conductor pipe is the largest diam.
Casing string :
 Offshore : 30 – 42 inch. or 76 – 107 cm
 Onshore: 16 inch. or 40 ½ cm
• Conductor Casing is usually no
more than 20 to 50 feet long.

Conductor Casing
• It is installed to prevent the top of the
well from caving in & isolates any
near surface & fresh water.
• It serves as a route for the drilling
mud coming from the well to the mud
tanks.

Surface Casing
• Surface casing is the next type of
casing to be installed after conductor
casing.
• It can be anywhere from a few
hundred to 2,000 feet long, and is
smaller in diameter than the
conductor casing ( 13 ¼ inch or 35
cm.)

Surface Casing
• The primary purpose of surface
casing is to prevent soft, near
surface sediments from caving into
the well.
• It also protects fresh water
reservoirs from further
contaminating by drilling mud.

Surface Casing
• It also serves as a conduit for
drilling mud returning to the surface.
• It helps protect the drill hole from
being damaged during drilling.

Intermediate Casing
• Intermediate casing is can be set to
isolate problem zones in the well
such as abnormal high pressure
, lost circulation, or a salt layer.
• It is typically 85/8inch ( 22 cm) .

Production Casing
• Production casing, alternatively
called the 'oil string' or 'long string,’
is installed last and is the deepest
section of casing in a well.
• This is the casing that provides a
conduit from the surface of the well
to the petroleum-producing
formation.

Production Casing
• The final string of casing is the
“Production Casing” or “Oil String”
that runs down to the producing
zone.
• It is typically 5 ½ inch (14cm) in
diameter.

Well casing is a very important part of
the completed well.
In addition to strengthening the well
hole, it provides a conduit to allow
hydrocarbons to be extracted without
intermingling with other fluids and
formations found underground.

Instead of a casing string, a liner
string can be set on the bottom of the
well to save money.
While a liner string is very similar to
casing string in that it is made up of
separate joints of tubing, the liner
string is not run the complete length
of the well.
A liner string is hung in the well by a
liner hanger, and then cemented into
place.

The section of the liner in the pay zone
may be wire wrapped screen pipe
with openings as small as (0.008 inch)
or perforated pipe may be used with
openings as large as ½ inch or above.

The liner may extend up into the
production casing only a short
distance and be sealed to the
production casing with a packer , or if
desired, may be extended to the
casing head on the surface, thus
forming an inner producing string.

Casing Programs
• Sometimes the well is drilled in
stages called a casing program.
• A well is drilled to a certain
depth, cased and cemented, and
then the well is drilled to a deeper
depth, cased and cemented
again, and so on.
• Each time the well is cased, a smaller
diameter casing is used.

After running in the casing string to
the desired depth, it is cemented
place.
A cement slurry is then pumped down
the casing and up around the outside
of the casing in the annular space in
the hole to the height desired and
there the cement is allowed to set &
harden to permanently fix the casing
in place.

The wall of hardened cement keeps
the hole from caving, which might
collapse the casing and to make the
secure in the hole.

After the casing is installed, tubing is
inserted inside the casing, running
from the opening well at the top to the
formation at the bottom.
The hydrocarbons that are extracted
go up this tubing to the surface.

Small diameter pipe called tubing is
run into the well to just above the
bottom to conduct the water, gas and
oil ( produced fluids) to the surface.

Tubing protects the casing from
corrosion by the producing fluids.
Since the casing is cemented in the
wall, it is very difficult to repair the
casing.
The tubing string is suspended in the
well, so, it can be pulled from the well
to repair or replace it during a “work
over”

Well completion commonly
refers to the process of
finishing a well so that it is
ready to produce oil & NG.

There are a number of types of
completion depending on the
characteristics and location of the HC
formation to be mined:
 Open Hole Completion
 Conventional Perforated Completion
• Sand Exclusion Completion
• Permanent Completion
• Multiple Zone Completion
• Drain hole Completion

Open Hole Completion
• Used in very competent formations.
• Consists of simply running the
casing directly down into the
formation, leaving the end of the
piping open.
• There is no production casing over
the oil or gas zone.
• This is a very primitive way to
complete a well.

Conventional Perforated Completion
• A modern well is completed with
steel casing set over the oil zone.
• It consists of production casing
being run through the formation.
• The sides of this casing are
perforated with tiny holes along the
sides facing the formation, which
allows for the flow of HCs into the
well hole.

• Perforation involves the use of
specialized equipment designed to
make tiny holes through the
casing, & cementing lying in
between the formation and the open
hole.

• In the past, “bullet perforators” were
used which were essentially small
guns lowered into the well.
• The guns were when fired from the
surface, sent off small bullets that
penetrated the casing and cement.
• Today, “jet perforating” is preferred
consisting of small, electrically ignited
charges that are lowered into the well.
When ignited, these charges poke tiny
holes through the formation.

Then a device called a "perforating gun"
(A) is lowered into the hole at the depth
where the oil or gas formation is
found. This may be anywhere from
several hundred feet down to tens of
thousands of feet.

After the gun is lined up properly, powerful
shaped explosive charges are fired (B) from
the control panel in the truck located up at
ground level. These explosives blast a hole
in the steel casing and cement, up to
several feet out into the rock. Finally, the oil
and gas fluids flow into the holes and up
the well to the surface (C).

This method of completion is much
better than the old open-hole method
shown in the first picture.
The PG is able to control exactly where
the perforations go.
This helps to limit the amount of
undesirable fluids, like salt water,
entering the hole, and maximize the
amount of hydrocarbons that can be
extracted from the well.

Sand Exclusion Completion
• Sand exclusion completions are
designed for production in an area that
contains a large amount of loose sand.
• This completion is designed to allow
for the flow of natural gas and oil into
the well, but at the same time, prevent
sand from entering the well as the
sand inside the well can cause many
complications (erosion of casing &
other equipment).

Sand Exclusion Completion
• The most common method of keeping
sand out of the well hole are:
 Screening or Filtering system.
• This includes analyzing the sand and
installing a screen or filter to keep the
sand particles out.
• This filter may either be a type of screen
hung inside the casing, or adding a layer
of specially sized gravel outside the
casing to filter out the sand. Both of these
types of sand barriers can be used in
open hole & perforated completions

Permanent Completion
• In this, the completion and wellhead
are assembled and installed only
once.
• The tubing is lowered to the desired
depth before perforation and not
removed during the life of the well.
All other operations are carried out
through tubing.
• Completing a well in this way can
lead to a significant cost savings.

Multiple Zone Completion
• In this practice, the HCs from two or
more formations may be produced
simultaneously, without mixing with
each other.
• eg. A well may be drilled that
passes through a number of
formations on its way, it may be
efficient in a horizontal well to add
multiple completions to drain the
formation most effectively.

Multiple Zone Completion
• Although it is common to separate
multiple completions so that the
fluids from the different formations
do not intermingle.
• If the different formations being
drilled are close enough in nature to
allow fluids to intermingle in the well
hole and it is necessary to separate
different completions, hard rubber
“packing” are used .

Drain hole Completion
• It is a form of horizontal or slant
drilling.
• It consists of drilling out
horizontally into the formations from
a vertical well, essentially providing
a “drain” for the HCs to run down
into the well.

The well head consists of equipments
on the surface that:
 supports the various pipe strings
 seals off the well to prevent leaking
of oil or NG out of the well.
 controls the flow rates of reservoir
fluids.

• Each string of casing usually hangs
from a casing head.
• The casing heads consists of heavy
steel fitting at the surface.
• It support the entire length of casing
that is run all the way down the well.
• “Metal and rubber seals” in the
casing head prevent fluids from
moving within the wellhead or
escaping to the atmosphere.

• Each casing head also has a place
for a pressure gauge to warn of
leaks.
• This typically contains a gripping
mechanism that ensures a tight seal
between the head and the casing
itself.

• “The Tubing head” is much like the
casing head.
• It provides a seal between the
tubing , which is run inside the
casing.
• It provides connections at the
surface, which allow the flow of
fluids out of the well to be controlled.
• The tubing head stacks above the
uppermost casing head.

• “The Christmas Tree” fits atop the
casing & tubing heads.
• It contains tubes and valves that
serve to control the flow of HCs and
other fluids out of the well.
• It commonly contains many branches
and is shaped somewhat like a
tree, thus its name, Christmas Tree .
• This is the most visible part of a
producing well and allows for surface
monitoring & regulation of the HC
production from producing well.

“The Christmas Tree” or "tree", is not
not "wellhead" as sometimes
incorrectly referred to.
• Note that a tree and wellhead are
separate pieces of equipment not to
be mistaken as the same piece.
• A wellhead must be present in order
to utilize a Christmas tree and a
wellhead is used without a
Christmas tree during drilling
operations etc.,

Once the well is completed, it begins to
produce.
HCs existing in pressurized formations
will naturally rise up through the well to
the surface. This is most commonly the
case with natural gas and light crude.
Since natural gas is lighter than air,
once a conduit to the surface is opened,
the pressurized gas will rise to the
surface.
Thus, once the CT is installed, the NG
will flow to the surface on its own

When a well is first drilled, the
formation is under pressure and
produces O&G at a very rate.
However, as more & more crude is
extracted from the formation, the
production rate of the well is decreased.
This is known as the “decline rate”.
During this time, application of certain
techniques including “Lifting
Equipment” & “Well Stimulation” can
increase the production rate of a well.

Lifting equipment consists of a variety
of specialized equipment that are used
to help “lift” petroleum out of a
formation .
This is most commonly used to extract
oil from a formation.
When oil is found as a viscous liquid, it
becomes difficult to extract it from
underground.

Various types of lifting equipment are
available, but the most common lifting
method is known as “Rod Pumping”.
Rod pumping is powered by a surface
pump that moves a cable and a rod up
and down in the well, providing the
lifting pressure required in the
well, providing the lifting pressure
required to bring the oil to the surface.

Well Treatment or Stimulation is
another method of ensuring the efficient
flow of HCs out of a formation.
Essentially, this type of well stimulation
consists of injecting stimulation
consists of injecting acid, water or
gases into the well to open up the
formation and allow the crude to flow
through the formation more easily.

“Acidizing” a well consists of injecting
acid (usually HCl acid) into the well.
In Limestone or Carbonate formations,
the acid dissolves portions of the rock
in the formation, opening up existing
spaces to allow for the flow of
petroleum.

“Fracturing” consists of injecting a fluid
into the well, the pressure of which
“cracks” or opens up fractures already
present in the formation.
In addition to the fluid being injected,
“propping agents” are also used. These
propping agents can consists of sand,
glass beads, silica sand etc. and serve
to prop open the newly widened
fissures in the formation.

“Hydraulic Fracturing” involves the
injection of water into the formation,
while CO2 fracturing uses gaseous .
Fracturing, Acidizing and Lifting
Equipment may all be used on the same
well to increase permeability.
These techniques are mostly used in oil
wells, but have also been used to
increase the extraction rate of gas wells.

Drilling Preliminaries Steps

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