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OVERVIEW OF
DRILLING OPERATION
BY
ENGR. AYODELE BELLO
CONTENT
• Definition of drilling
• Types of wells drilling
• Types of drilling rig & personnel
• Rig components
• Casing & cementing
• Hole problems
• Fishing operation.
• Conclusion
Drilling operation
 Definition: application of science and
technology to make a hole through the earth
crust.
 Equipment that drill is called the rig.
 The unit of measurement is feet (meter)
 Rig are mobile, they can be assembled (rig up)
or rig down at the location
 Different environment require different types of
rig.
Application of drilling
• Drilling is the only means to
ascertain the presence of oil in the
formation.
• Drilling provides a means of
producing reservoir fluid.
• Drilling provides a means of
communicating with the reservoir or
subsurface.
• For water and mineral, construction
e.t.c.
Pre-spud meeting
• The opco advertises to contractors to submit
tenders
• After rig/contractor is decided, meetings are held
to discuss things like:
mud program, bit program, casing program,
various contractor needed to supply things like
water, catering services, laundry, security e.t.c.
• Well engineering is planned and data from offset
well that can help the drilling company is
provided to aid planning.
Factors considered in Well planning.
Selection of the location
• After the prospect to be drilled has
been identified, the exact location for
drilling is chosen based on various
factors like accessibility, level ground,
ease of communication e.t.c. This is
the first step in well drilling.
Collect pressure data
• Once the location has been identified,
geological data of adjoining wells is
collected and analyzed.
• Special emphasis is laid on pressure data
like expected formation pressure, fracture
gradients and formation stability
• In cases where no wells have been drilled
previously these pressure are estimated
from geophysical data collected while
prospecting.
Decide target depth
• Before any drilling activity can begin, the
target depth of the well to be drilled is
decided.
• This is because an oil well is usually drilled
in three or less section known as phases if
there is no hole problem.
• This is to ensure optimum use of men and
materials
Decide hole geometry
• An oil well is usually drilled in phases –
each succeeding phase being smaller in
diameter than the preceding phase.
• The exact configuration of these phases
i.e the hole diameter and the exact depth
to which each phase will be drilled is
decided.
• The casing sizes are based on the hole
sizes
Decide casing setting depth
• Once a particular diameter hole is drilled it
is cased and cemented to prevent
formation collapse.
• The formation strength, the fracture
gradient and the possible formation
pressure is considered to determine when
it is safe to set casing to prevent formation
breakdown or influx of formation fluid to
the well bore.
Decide cement plan
• Cementation is done to hold the casing in
place.
• This helps to hold the casing by forming
bond between the formation wall and the
casing.
• To do this, the volume of slurry required to
fill up the annulus has to be calculated, the
type of cement to be used, the cement
additives, the composition of the cement
slurry must be well planed and
documented.
Mud program
• Drilling fluids are required to drill an oil
well.
• Details about the type of mud, the mud
properties and the various mud additives
to be used for drilling the well are laid out
in mud program.
Design drilling program
• Detailed specifications about the various
drilling parameters at various depths like
weight on bit (WOB), rotation per minute
(RPM), pump pressure and flow rate of the
drilling mud are taken into consideration in
well plan.
• In addition the type of drilling whether vertical
or deviated is also specified in the drilling
plan
Design bit program
• Specification of the various drilling bits to
be used at various depths are mentioned
here.
• The type of bits to be used, the size of bit
& nozzle sizes to be used and the various
hydraulic parameters to be maintained are
also discussed.
Design formation evaluation
program
• The process of identification, location and
appraisal of formations containing oil, by the
well site geologist as the drilling continues is
known as formation evaluation.
• Formation evaluation is done with the help of
logging techniques such as wire line logging,
mud logging, coring & cutting analysis.
• Details of the kinds of logging to be done, their
frequency and depths to which electric logs will
be run are mentioned in the formation
Completion plan
• A general idea about the method to be
used to produce the well after completion
of drilling is itemized in the completion
plan.
• Completion can be open hole, cased hole
with single tubing or cased hole with
multiple tubing’s and packers.
Testing program
• The kind of testing which will be done
upon completion of drilling is specified in
testing plan.
• The type of testing to be done and at
which depth, may be open hole testing or
cased hole, it must be specified here.
Select rig
• The rig selection is primarily based upon
the total depth to be drilled.
• This is because the drilling capacity of a
rig will depend upon its load carrying
capacity as it will have to lift a heavier load
to drill deeper.
• Thus to drill a deeper hole a higher
capacity rig is used
Project drilling time
• Based on the various factors, the total
time required to drill the well and complete
it are estimated.
• In addition to the total time, a detailed
break up of drilling days versus depth and
the time required for various activities like
casing e.t.c is also made.
• This estimate is generally very accurate
and drilling is usually completed according
to plan
Estimate costs.
• An accurate estimate of the cost of drilling
the well is made.
• These costs falls into two broad
categories, for consumables and for
services required.
• The cost of services required is usually
dependent on the total number of days
required to drill the well.
• The amount of consumables will depend
on the target depth of the well.
Drilling contract
• For effective drilling operation both in
terms of cost, safety and timeliness, a
detail contract is entered into between the
operator and the drilling contractor.
• This is aimed at drilling usable hole for the
operator efficiently, safely and
economically.
• Different types of contract are available
depending on the agreement between the
operator and the drilling contractor
Day rate
• The rentals for rig and personnel charges
are based on the number of days that the
rig is on site irrespective of the number of
meters/feet drilled per day.
Footage/Meterage rate
• The rental for rig is based on the number
of meters/feet that the rig drills at a
particular location, irrespective of the
number of days on location.
Turnkey
• Here all the services required to drill and
complete a well are to the drilling
company.
• That is the sum total of the cost required to
drill the well to TD is paid the contractor
irrespective of number of days spent on
location and the number of feet/meter
drilled per day.
• This contract type is more popular as it
increases the efficiency of drilling
company.
Types of oil wells drilled.
 Exploration Well - A well drilled for
the purpose of ascertaining or
confirmation of oil accumulation.
 Appraisal wells are drilled to
determine the extent of the reservoir,
so as to know volume of the oil
reserve.
 Development wells (Infill drilling or
Well) – This is a well drilled to
optimize oil production form a given
reservoir or field.
 Directional Well. This is the science
of directing a wellbore along a
predetermined trajectory to intersect
a designated sub – surface target.
 Horizontal Well drilling is the
science directing a wellbore along a
predetermine trajectory usually at an
angle of 900 to the vertical to
intersect a designated sub- surface
target
TYPES OF DRILLING RIGS
It is always desired to drill in different geographic
and climatic environment.
However, the basic drilling operation remains
essentially the same regardless of the types of
rig used or the environment where the rig is
used.
 LAND LOCATION (ON SHORE)
 land rig is used which consist of derrick or
mast, substructure, mud pit, drillers cabin,
prime movers, hoisting equipment, rotating
equipment, circulating equipment and crew
residential cabin.
WATER DRILLING EQUIPMENT
(MODU)
• Inland water equipment – Inland water
drilling includes swamp, dredged marsh,
bay and lagoon locations where water is
relatively shallow and protected from
appreciable wave action.
• Submersible (Inland Barge) drilling
barge is used. Inland barges are designed
for drilling in 10 – 20 ft of water.
• Drilling in deeper water with submersible
barge is accomplished by construction of a
shell gravel fill for the barge to rest on.
Jack – up rig
 May be used from 50 ft to 350 ft of
water.
 The cost of such installation is enormous,
but may be quite economical on a per well
basis, since numerous wells may be
directionally drilled from its deck.
 They are very useful in development
drilling and poorly adapted to exploratory
work
Jack – up rig
Semi submersible Rig
 These types of rig are often refers to as
semi for short.
 They are floating barge.
 They use anchors on the sea floor to keep
the rig stationary.
 They can be used in water up to 7000ft
(2100m).
 Water is allowed to enter the barge so as
to lower the rig to the sea level for drilling.
Semi submersible Rig
DRILLING SHIP (Floater)
 This is a large self contained ship, which
contains substructures, drawworks, rotary table,
engines, mud pits, dry mud, chemicals etc, pipe
racks, cementing equipment, fuel and water and
crew quarters.
 The ship can operate in any weather short of
hurricane. It can be used for a deep offshore
drilling and in remote areas.
 It uses dynamic positioning to keep them on
station (it uses computer controlled motors or
thruster and sensors)
DRILLING SHIP
THE OIL COMPANY
COMPANY MAN
SAFETY ENGINEER MARINE CREW
WELLSITE
GEOLOGIST
TOOL PUSHER
DRILLER
DERRICK MAN
ROUGHNECK
ROASTABOUT
MUD ENGINEER
CEMENT ENGINEER
WELL TESTING OPERATOR
CASING ENGINEER
DIRECTIONAL DRILLER
MUD ENGINEER
CORING ENGINEER
MUD LOGGING
ELECTRIC LOGGING
FIGURE SHOWING THE INTERDEPENDENCY OF VARIOUS PERSONNEL INVOLVED IN DRILLING OPERATION
DRILLING RIG PERSONNEL
Crews may consist of four, five, six, or
more individual depending on the size
and service rating of the rig itself.
TOOLPUSHER
The Tool pusher – sometimes called
the rig superintendent or rig manager –
is the man in charge of the rig and
overall drilling operations.
Driller - is directly in charge of drilling
activities; he supervises other workers
in the rig. He is next to the tool pusher.
DRILLING RIG PERSONNEL
 Derrick man or assistant driller – he is
next to the driller, stays at the monkey
board to control the pipe during tripping.
 After tripping he monitors the mud.
 Floor man or roughneck – they are in
charge of making up and breaking out drill
pipe while drilling or tripping.
 Motorman, Mechanics, Crane
operator and roustabout e.t.c.
MAJOR COMPONENT OF
DRILLING RIG
 Power system (prime mover)
 Hoisting (Drawworks, Blocks and
drilling line, Derrick)
 Rotary system (Swivel, (Kelly, Rotary Table) Top
Drive system , Drill pipe, Drill collar & Bits)
 Circulating system (Drilling fluid, Mud pumps,
Mud tanks, The mud cycle (desilter, dessander,
degasser))
 Well Control system (Blowout Preventer,
Accumulator, Diverter)
PRIME MOVERS
 Prime mover provide power for the rig.
 It is usually an internal combustion engine.
POWER
 1 hp = 33,000ft – lb/min. The amount of power required
for drilling varies with the job, but most rigs require from
1,000 to 3,000hp, usually provided by two or more
engines.
 Shallow or moderate – depth rigs need from 500 to
1,000hp for hoisting and circulating, heavy-duty rig may
require 3,000 hp or more. The power requirements for
rig auxiliaries such as lighting and air conditioning may
be from 100 to 500 hp.
 Power Transmission: A rig may have a mechanical
drive or an electric drive (which may be an AC – DC
drive or DC – DC drive).
HOISTING SYSTEM
Derrick or Mast
 Derricks and portable masts provide the clearance and
structural support necessary for raising and lowering drill
pipe, casing, rod strings, etc., during drilling and servicing
operations.
 The derrick or mast must be designed to safely carry all
loads that are likely to be used during the structure’s life.
 Wind load and compressive load.
 Wind load is given as: P = 0.00338 (V2)(Ch,)(Cs)
P = pressure in. lb/ft2
V = wind velocity in knots
Ch = height coefficient
Cs = shape coefficient (1.25 for derrick)
 Derrick load* = 1.5(Wh + Wc + Wt + 4FL)
HOISTING SYSTEM
DRAWWORKS
 The drawworks, is a big heavy piece of machinery that
consists of a revolving drum around which the wire rope,
called the drilling line is spooled or reeved.
 It also has a cat shaft, a kind of axle that crosses
through the drawworks that has a revolving drum (called
a cathead spool) on either end or two special catheads.
 Several other shafts, clutches and chain and gear drives
facilitate speed and direction changes.
COMPONENTS PARTS
 Drillers Console, brake lever, drum shaft, sprocket, gears
and chains. It also contains drum brake and equalizers,
cat shafts with cat heads.
Functions of Drawworks
 Transmit power from the prime mover to its hoisting
drum to lift drill string, casing string or tubing string or
to pull in excess of these string loads to free stuck pipe.
 Transmit power to the catheads for breaking out and
making up drill string, casing and tubing string.
 Transmit power from the prime movers to the rotary
drive sprocket to drive the rotary table.
 The hoist contains brake systems which enable the
driller to easily control a load of thousands of pound of
drill pipe or casing. There may be at least 2 types of
brake system.
 1) The mechanical and (2) Hydraulic or
hydrodynamic or electric
The drawworks on the rig floor
BLOCKS AND DRILLING LINE
 The drilling line supports the entire drilling
assembly by means of pulley – style devices and
grasping implements, which are collectively
called the overhead tools.
 Included among these are the crown block,
traveling block, the hook, drilling line and the
elevators.
CROWN BLOCK
 The crown block is an assembly of sheaves
mounted on beams at the top of the derrick.
Most crown block has 4 to 7 (seven) sheaves
which may be as large as 5 – feet in diameter
mounted in line on a common centre pin.
Crown block
TRAVELING BLOCK
• The traveling block moves
between an up and a down
position on the line.
• It carries the hook that support
drill string when drilling and the
elevator bail that holds the
elevator when tripping in or out of
the hole.
• Selecting a block for a certain rig
or for a certain job depends on the
block load capacity in tons
HOOK
 The hook is a large joining device suspended
from the traveling block to grip the various
piece of equipment needed in drilling and in
making trips.
 It rotate on bearing in its supporting housing
and can be locked into many as twelve
different position.
 The hook has a safety latch for the swivel
and locking arms or link ears at both sides
for elevator – bail attachment.
Hook schematics
DRILLING LINE
 Drilling lines are made of steel wires that
are made into strands and the strands into
rope in action similar to braiding.
 The outer strands are laid spirally around
a central core.
 The wire rope generally ranges from 1 1/8
to 11/2 inches
 The important things to watch out for to
prevent wear to drilling line are: the tread
diameter of the block sheaves, the
critical points, groove radius, fleet
angle and prevent sudden loading.
ROTATING SYSTEM
 The rotating equipment from top to bottom consists of
the swivel, Top Drive System (TDS) (the Kelly), the
rotary table, the drill stem and the bit.
 The drill stem is the assembly of the swivel and the bit
(i.e. drill pipe and drill collars, stabilizer e.t.c.)
SWIVEL
 Swivel in a device joining two parts so that one or both
can pivot freely. It is attached to the traveling block by a
large bail. It may rotate more than 200rpm.
FUNCTION OF SWIVEL
 It supports the weight of the drill stem
 It allows the drill stem to rotate
 It provides a pressure – Tight seal and passage way for
the drilling mud to be pumped down the inside of the drill
stem
 Pronounced on a Kelly rig.
KELLY
 The Kelly is a square, hexagonal or triangular piece of
pipe, usually about 40 ft long, which serves the purpose
of transforming the rotating motion of the rotating table to
the drill string
FUNCTION OF KELLY
 It serve as a passageway for drilling fluid on its way into
the drill pipe .
 It transmits the rotating movement to the drill pipe and
bit.
 It may serve as well control equipment through upper
and lower Kelly cock.
 The Kelly fits into a corresponding square or hexagonal
opening in a device called a Kelly bushing or drive
bushing. The Kelly bushing fits into a part of the rotary
table called the master bushing or rotates and as the
Kelly rotates, the drill string and bit rotate.
THE ROTARY TABLE
The function of rotary table is to:
• To turn and rotate the Kelly (or any equipment
attached to it)
• To support the weight of the drill string or the
casing during make up or break out
• When drilling is going on, the rotating turns to the
right or clockwise.
• When the pipe is pulled from the well bore, the
rotary table supports the string on slip during
intervals when pipe is not being suspended from
hook.
• The rotary table rotates through a working range
of 40 – 50 to 200 revolutions per minute (rpm).
As the hole deepens the Kelly descends through
the bushings, which are mounted in the table
openings.
Rotary table
TOP DRIVE SYSTEM (TDS)
• It provides rotation for the drill string
instead of rotary table in Kelly rig.
• It consists of gear box, one or two
hydraulic motors, a pipe handler or
grabber which includes torque arrestor.
• It also has guide and torque track
which terminates 7-9 feet above drill
floor and elevator links including
elevator.
• The speed can be up to 600 rpm.
DRILL STRING
 The drill string is made up of the drill pipe and special heavy –
walled pipe called drill collars.
DRILL PIPE
 Each length of drill pipe is about 30 ft long and is called a joint
of pipe.
 Drill pipe is attached to Kelly at the top (on a Kelly rig) but
connects to the TDS and to the drill collar (HWDP) at the
bottom.
Function of Drill Pipe
 Permit rotation
 Allow fluid passage to the bit.
 Provide necessary length of the well drilled
Each end of each point is threaded.
 The end of the joint with interior threads is known as the box,
and the end of the joint into the exterior threads is called a pin.
 The joints are welded to the body of the pipe.
DRILL COLLAR
 These are heavy walled pipe of small diameter steel
tubes, like drill pipes, through which mud can be
pumped. ROUNDED OR SQUARE (Drill collars)
 Drill collars are about 30ft long and unlike the drill
pipe that has tool joints welded on, they have the
boxes and pins cut into them.
FUNCTION OF DRILL COLLAR
 To transfer rotary action to the bit
 To allow passage for drilling mud
 To put weight on the bit
 To provide good stabilization for the bit to drill a
straight hole.
Rotating equipment.
 Heavy wall drill pipe (HWDP) - consist of
heavy wall tubes with an upset in the middle,
called the center wear pad.
 It is a transition between the drill collar (DC)
and the drill pipe (DP) to make the crossover
gradual.
 Stabilizers. These are drill string components
with blades that protrude from the body.
 They are usually almost the same diameter as
the bit and are located in a drill string at various
points in the drill collars of the BHA, including
just above the bit for directional/deviated hole
and far up or in the middle for vertical hole
drilling.
SUBS
 These are short sections of drill collars materials
about two feet (2 ft) or longer, which provides
crossovers between different diameters and
types of threaded connection.
 They are available in different connection
configuration such as: box / box, pin / pin, pin /
box and box / pin subs
 Crossover subs
 Float subs – a non – return valve run just
above the bit (to prevent kick through drill
string)
 Dart sub – a landing sub for a drop in and
pump – down back pressure valve.
 Its function is to prevent kick through drill string
like float sub.
 Bent sub.
BITS
 The drilling bit is attached to the drill collar through the
bit sub. This is the part of the rotary system that does
the actual hole making.
 THE DRAG e.g. FISH TAIL.
 it does not have a moving pact.
 It drills by shoveling action against the formation.
 The water course opening is directed against its blade so
that it can remove any shale that may be attached to the
cutting surface.
 It is used mainly to drill a soft formation, especially at a
shallow depth.
ROLLER CONE BIT
 It has cone – shaped steel devices called cones that are
free to turn as the bit rotates. Most bits have 3-cones,
but some have 2 and some have 4 cones
There are two types of Roller
cone bits:
• The steel tooth bit and (b) Tungsten –
carbide inserted bit
• All bits have passage drilled through them
to permit drilling fluid to exist.
• Jet nozzle opening.
• They can be used for both soft, medium
hard and hard formation depending on its
design.
• Roller bearing and journal bearing.
Tungsten carbide insert
DIAMOND BITS
 Since diamonds are so hard, diamond bits
are specially suited for drilling hard rock
formations but may also be used effectively
on soft formation.
 A PCD (polycrystalline diamond bit) is also a
type of drag bit.
 A cylindrical Coring bit is also available with
diamond studded.
A PDC bit for soft formation
CIRCULATING SYSTEM
 For the rotary drilling system to function, fluid must be
circulated downward through the drill stem, around the
bit and upward in the annular space between the drill
stem and the wall of the hole or the casing. (The
circulation route).
THE DRILLING MUD (FLUID)
 The term “drilling fluid” includes air, gas, water and
mud.
 The term “mud” refers to a suspension of solids in water
or oil or of solids and droplets of one of these liquids
(emulsion) dispersed in the other. The mixture of clay
(Solid bentonite) and water or oil is a mud.
The drilling mud consist of phases
 i. The liquid phase (water or oil) (may be fresh or salt
water)
 ii. The colloidal fraction (bentonite or Wyoming clay)
 iii. The inert fraction (barite, weighting material etc)
Functions Of Drilling Mud
To transport bit cutting to the surface
To clean the bottom of the hole (bit)
To cool and lubricate the bit and drill stem
To support the walls of the wellbore
To prevent entry of formation fluids into
the well i.e. control subsurface pressure.
To suspend cutting when circulation is
stopped.
THE MUD PUMP
 The function of the mud pump is to circulate
the drilling fluid from the tank, through the drill
stem, to the bit (where hydraulic power is
expended for jetting), back up the annulus and
back to the tank.
 The mud pumps are either Duplex, double –
acting pumps or triplex pump.
 The term “duplex” refers to the number of
pistons (2) and term “ double – acting” denotes
that each side of piston does work. Pulsating
discharge and high pressure.
 Triplex has 3 pistons and single acting. High flow
with smooth discharge.
Schematic valve operations for double acting
duplex pump
.
Piston
Piston rod
P2 Discharge
P1 inlet or suction
Pressure control system
 Pressure control system includes Blowout
Preventers (BOP), diverters, choke and kill line
and accumulator unit.
 Types of Blowout Preventer (BOP) (Annular
Preventer and Ram Preventer)
 Ram preventer has three types of rams (pipe
ram, blind ram and shear ram).
Functions of BOP
 To close the wellbore and contain pressures
 Allow wellbore fluids to be control vented.
 Allow pumping into the well (when usual means
are not available)
 Allow tripping of drill pipe into and out of the
hole
CASING
 Casing is a strong cylinder steel pipe used in an
oil well to ensure a pressure tight connection
from the surface to the oil or gas reservoir.
FUNCTIONS OF CASING
 To prevent cave-in or washout of the hole
 To prevent contamination of fresh water sands
by fluids from lower zone
 To exclude water from the producing formations
 To confine production to the well bore
 To provide a means of controlling well pressure
 To permit selective production of the pay zone
 To furnish a permanent borehole of precisely
known diameter
TYPES OF CASING
Drive Pipe
 It is used to prevent shallow formation damage and
collapse.
 It also provide support and passageway for the
conductor casing (Not always used especially in a
consolidated formation).
 Installed by driving the pipe to a point of refusal.
Off shore consideration
 Slip joint takes care of heaving up and down of the
water body
 Slip joint is connected to the marine riser at the bottom
and the vessel body.
 Flex Joints. A flex joint is installed between the lower
end of the riser and the BOP stack.
 This joint essentially acts as a pinned connection to
minimize bending stresses in the riser as the drilling
vessel is moved by wind, wave and current action.
A FLOATING DRILLING
SYSTEM
TYPES OF CASING
CONDUCTOR CASING
 Conductor pipe is used as a channel to raise the
circulating fluid high enough to return to the pit.
 It prevents erosion of the hole around the base of the
rig.
 It protects the subsequent casing strings from corrosion
and may be used to support some of the wellhead load
on location where ground support is not enough.
 May be set 300ft or more.
SURFACE CASING
 Surface casing is set deep enough to protect the well
from cave- in and washout of loose formations that are
often encountered near the surface.
 It provides a point of attachment for casing head and
other fittings that will be left on the completed well.
 Surface casing is usually set from 300ft to 4000ft.
INTERMEDIATE CASING
 The intermediate casing is to protect the hole (called
production or salt casing).
 It is used to seal off weak zones that may rupture with
heavy mud usually needed for deepening a well.
PRODUCTION CASING
 This string of casing serves to isolate the producing
reservoir from undesirable fluids in the producing
formation and from other zones penetrated by the well
bore.
 It is the protective housing for the tubing and other
equipment in a well.
LINER STRING
 A liner is an abbreviated string of casing used to case
open hole below existing casing.
 Production liners are sometimes suspended in the well
without cementing.
FORCES ON CASING
• The major forces acting on casing are:
• Tension: this is a downward pull of the
weight of the casing string on the pipe
body and on the coupling created at the
top of the casing string
Burst
• Burst pressure occurs when the pipes
internal pressure is greater than the
external pressure
Collapse
• This is an unbalanced external pressure
imposed on pipe.
PRIMARY CEMENTING
 Primary cementing is the process of
mixing and placing cement slurry in the
annular space between a string of casing
and another casing or casing and the open
hole.
 The cement sets, bonding the pipe to the
formation.
 Cement slurry is the mixture of dry
cement with water and necessary
additives to condition the slurry to suit the
hole characteristics.
CONDUCTOR PIPE 36” /
300’
SURFACE CASING 20”
INTERMEDIATE
CASING 13 3/8/ 5000’
PRODUCTION CASING
95/8”
LINER STRING 7”
Fig. 12.0 WELL SCHEMATICS SHOWING CASING STRINGS ASSEMBLY
CEMENTING TOOLS
 Cementing head, top plug, bottom plug, float
collar, centralizer, Guide shoe, Scratchers,
cement pump, cement mixer.
Guide Shoe
 A guide shoe is a round-nosed device installed
on the first joint of casing with thread – locking
compound.
 It has opening in the bottom to allow drilling
mud to enter the casing as it is lowered.
 It is always used.
 There are three types of guide shoes:
 1) Plain guide shoe, 2) The combination of float
and guide shoe, 3) Automatic fill-up guide shoe.
Float Collar
 This is similar to float shoe, it permits the
casing to float into the hole.
 The float collar may be installed on top of
the first joint or on top of the second or
third joint to go into the hole.
 Most operators employ a float collar at a
distance of one or more joints above the
casing shoe in order to provide space
inside the casing for contaminated
cement.
 Provide a stop point for bottom plug
 Centralizers
 These are steel metals used to keep the casing pipe
away from the borehole wall.
 They must be spaced close together enough to prevent
the casing from contacting the formation wall even in a
deviated hole.
They are used to:
 Ensure a reasonably uniform distribution of cement
around the pipe
 Obtain a complete seal between the casing and the
formation.
Cement Scratchers
 These are mechanical wall cleaning devices attached to
casing.
 They abrade the hole when worked by reciprocating or
rotating the casing string
 Ensure good bonding between the casing and the
formation.
Bottom plug (Wiper plug)
 The bottom plug is a cylindrical hollow molded rubber
body.
 It contains diaphragm at the top which rupture to
allow cement slurry to flow through and also has
wipers protruding from its side that removes mud.
 It is the first plug to go into the casing from the
cementing head.
 It wipes mud off the inside of the casing and keeps the
mud separated from the cement.
Top Plug (Wiper plug).
 The top plug is a solid cylindrical core with four wipers
protruding from its sides.
 The top plug follows the cement into the casing and
wipes cement off the inside wall of the casing.
 It also prevents the mixing together of cement and the
displacement fluid behind the cement.
 This plug is solid. When it seats or bumps on the
bottom plug at the float collar, pump pressure
increases since no fluid can get pass the top plug.
Cement Head.
 This house the wiper plugs and also the
cementing line is attached to it.
 The cement flows into the casing through the
well head and also provides a channel
through which the drilling mud in the
annulus flows to the surface.
A centralizer, scratchers, guide shoe and float collar.
DRILLING PROBLEMS
 A lot of hole problems are encountered
and may be avoided or overcome by
proper control of mud properties.
These are:
 Salt section hole enlargement
 Heaving shale problems
 Blowouts
 Lost circulation
 Formation damage
 Key seating
 Bit balling
HOLE EROSION
CAUSE
 Hole erosion results from the hydraulic impact on formations
with poor inter-grain cementation.
 Generally it is caused by turbulent fluid flow in the annulus or
excessive circulation in one place with the bit off bottom.
Effect
 The annular fluid velocity will be reduced in enlarged hole
sections. If the drilling fluid is not highly pseudoplastic, the
cuttings can concentrate in this area.
 Eventually they may form a 'mud ring' or ball of
agglomerated cuttings, which in severe cases can lead to
hole pack-off and stuck pipe.
 Good cementing practice requires turbulent flow to ensure
proper drilling fluid removal.
 Large washed out sections may cause the flow to become
laminar and poor drilling fluid removal.
PREVENTION
 -Keep the flow regime laminar, where
possible. Maintain highly pseudoplastic
rheology
 -Low shear rate viscosity along with the
reduced flow rate requirements this makes
an excellent fluid for unconsolidated
formations.
 -In silty formations examine the possibility
of water sensitive clays causing further
destabilization. If suspected, test with
small treatments of inhibiting chemicals or
polymers.
SALT SECTION HOLE ENLARGEMENT
 When salt domes are penetrated, they dissolved, eroded,
thus causes an excessive hole enlargement, which in turn
may be a source of future trouble and expense
 In case of drill string failure, the enlarged hole makes
fishing operation (attempts to retrieve the drill string)
exceeding difficult
 Larger mud volumes are required to fill the system hence
treating cost are higher
 Large cement volumes are required for casing operation if
fill – up through the section is to be attained
Solution.
 The principal means of avoiding these problems is to
prepare a salt saturated mud system prior to drilling the
salt, thus avoiding the dissolving effect.
HEAVING SHALE PROBLEMS
 Some areas are characterized by shale sections
containing bentonite or other hydrated clays, which
continually absorb water, swell and slough into the hole.
 This often occurs in the younger formations in the upper
hole sections. It is the result of water imbibition by a
smectitic shale.
 They can cause pipe sticking, excessive solids build up
in the mud and the hole bridging are typical resultant
problems.
 The annular diameter is reduced. The drill string, logging
tools and casing may not easily pass through.
 Increased annular friction pressure losses may raise the
ECD above the fracture pressure for a lower zone. .
 Sloughing shale can also be caused by brittle failure
resulting from differential rock stress.
Heaving shale.
This can be due to tectonic activity or deviation of the well bore from
vertical.
Hole collapse by caving in
The rock can fail in either tension or compression depending
upon the orientation of the stresses to the wellbore wall
SOLUTION TO HEAVING SHALE
 Changing mud system to inhibitive type
e.g. lime, gypsum which reduces tendency
of the mud to hydrate water sensitive
clays
 Changing to oil emulsion mud or oil base
mud
 Increase circulation rate for rapid removal
of particles
 Maintaining a positive pressure
overbalance against the formation
pressure will help to hold the failed rock
pieces in place
DIFFRENTIAL PRESSURE STICKING
 This is the force that holds pipe against the wall
of the hole, due to the differential between
formation pressure and hydrostatic pressure
 Circulation is not hindered.
For differential sticking to occur the following
criteria are required:
 Hydrostatic pressure must exceed formation
pressure.
 A zone of permeability must exist, over which a
thick filter cake has been deposited.
 There must be contact between the pipe and the
filter cake
Differential pressure sticking
KEY- SEATING
 A key seat results when drill pipe under tension
wears a slot into the wall of the hole during
drilling and tripping operations.
 It often occurs when drilling a directional well.
 The slot diameter is usually the same as the
diameter of the drill pipe tool joints.
 The drill collars are therefore most likely to get
jammed in a key seat when pulling out of hole.
Recognizing key-seating
 Key seating is indicated by an increasing over
pull, normally during tripping.
 Here again the circulation is not impeded after
the string has become stuck.
Key seating The development of a key seat
BLOWOUTS
 A blowout occurs when formation pressure exceed
the mud (hydrostatic) pressure which allows the
formation fluid to flow out of the hole.
 This is one of the most expensive and highly feared
hazards of drilling
Blowout may occur due to:
 Swabbing i.e. pipe pulling (suction) out of the hole
too rapid
 When a zone of high pressure (gas zone) is
encountered
Solution.
 The solution is to drill with proper mud density to
overcome the encountered subsurface pressure
LOST CIRCULATION
Lost circulation is defined as the loss of substantial quantity of mud or
whole mud to an encountered formation.
 This is shown by complete or partial loss of returns (annular mud return)
 Drop in annular mud volume may also cause kick
Types of formation to which circulation may be lost are:
 Coarsely permeable rocks e.g. gravels, reef, and irregular limestones
 Faulted, jointed and fissured formations such as
 Those with naturally occurring fractures
 Those in which the fractures are induced or caused by column
pressures
 Cavernous and open fissured formations
Prevention
 Minimum overbalance of hydrostatic head, plus ECD.
 Cure
 Cut down the pump rate , reduce the overbalance , block the permeable
channels by pumping LCM.
FORMATION DAMAGE
 Formation damage is caused by the invasion of foreign
fluids and / or solids into the exposed section adjacent to
the well bore.
 Generally, the drilling mud is the main source of such
contaminants.
 Fluids used in stimulation treatment (acidizing, hydraulic
fracturing etc) may also have some undesirable effects,
which partially nullify their beneficial actions.
 This damage when it occurs in the pay zone hinders or
prevents the flow of oil or reservoir fluid into the well bore
or production tubing.
JAMMING A NEW BIT
 An undergauge hole is a section of a hole with a smaller
diameter than the diameter of the new bit used to drill
ahead.
 The most common cause of under-gauged holes is
gauge wear on the previous bit run
DRILLING LINE SERVICE
 (Ton – miles of Drilling line) uses Lb-ft
 The amount of wear a drilling line suffers is
closely related to the amount of work it helps
accomplish.
 Ton – miles of service are accumulated on:
 round trips ,
 in drilling,
 coring,
 reaming,
 fishing and
 running casing – in fact, during any operation
that entails putting any load on the drilling line.
 Tables are available to assist in calculating
drilling line service
Fish and fishing operation
• Fishing is the act of retrieving any lost or
stuck tool from the well bore.
Tools used includes:
• Free point detector
• String shot back off
• Jet, chemical cutters
• Wash over pipe
• Overshot
• Spears
• Jars and accelerators
• Impression block
• Tapered tap e.t.c.
DOWN HOLE MOTORS
Turbine Motors
 The activating drilling mud or freshwater is pumped
at high velocity through the motor section, which,
because of the vane angle of each rotor and stator
(which is a stage), causes the rotor to rotate the
shaft of the motor.
 The kinetic energy of the flowing drilling mud is
converted through these rotor and stator stages
into mechanical rotational energy.
 The rotors are forced to turn, causing the bit to
rotate.
 The major advantage of turbine is that they can
operate at higher temperature than the PDMs.
Positive Displacement Motors
 A positive displacement motor (PDM) also drive the drill
bit independent of the drill string rotation.
 Soft, medium and hard rock formations can be drilled
with a positive displacement motor using nearly any type
of rock bit.
 Rather moderate flow rates and pressures are required
to operate the positive displacement motor.
 Thus, most surface pump systems can be used to
operate these downhole motors.
 Rotary speed of the positive displacement motor is
directly proportional to flow rate.
 Torque is directly proportional to pressure. Thus, normal
surface instruments can be used to monitor the
operation of the motor downhole.
 High torques and low speeds are obtainable with certain
positive displacement motor designs, particularly, the
higher lobe profiles.
DIRECTIONAL DRILLING
 The common method of drilling a directional well
is to use a downhole motor with a bent sub.
 The bent sub is directly placed above the motor.
 It is the bent sub which makes the deflection
assembly, its lower thread is inclined 10 to 30
from the axis of sub body.
 Downhole and the bent sub assembly can be
used for kicking off wells, for runs correction and
for side tracking.
 Whipstocks (standard removable & permanent
casing whipstock) can be used to kick off well by
applying weight to set it and shear its pin.
 But may lead to severe dogleg and lots of rig
time in tripping and opening the rat hole.
DIRECTIONAL DRILLING
• Jetting (or badgering) is a technique
used to deviate wellbore in soft
formation.
• A special jet bit is used and the
formation must be soft enough to
erode by the action of drilling fluid.
• Also adequate rig hydraulic
horsepower must be available to
erode the formation.
conclusion
We have seen different types of:
 Rigs
 Drilling techniques (onshore &
offshore)
 Vertical and directional well
 Hole problems and possible solutions
 Fishing operations
Let us complete the well.

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overview of DRILLING OPERATION.pptx

  • 2. CONTENT • Definition of drilling • Types of wells drilling • Types of drilling rig & personnel • Rig components • Casing & cementing • Hole problems • Fishing operation. • Conclusion
  • 3. Drilling operation  Definition: application of science and technology to make a hole through the earth crust.  Equipment that drill is called the rig.  The unit of measurement is feet (meter)  Rig are mobile, they can be assembled (rig up) or rig down at the location  Different environment require different types of rig.
  • 4. Application of drilling • Drilling is the only means to ascertain the presence of oil in the formation. • Drilling provides a means of producing reservoir fluid. • Drilling provides a means of communicating with the reservoir or subsurface. • For water and mineral, construction e.t.c.
  • 5. Pre-spud meeting • The opco advertises to contractors to submit tenders • After rig/contractor is decided, meetings are held to discuss things like: mud program, bit program, casing program, various contractor needed to supply things like water, catering services, laundry, security e.t.c. • Well engineering is planned and data from offset well that can help the drilling company is provided to aid planning.
  • 6. Factors considered in Well planning. Selection of the location • After the prospect to be drilled has been identified, the exact location for drilling is chosen based on various factors like accessibility, level ground, ease of communication e.t.c. This is the first step in well drilling.
  • 7. Collect pressure data • Once the location has been identified, geological data of adjoining wells is collected and analyzed. • Special emphasis is laid on pressure data like expected formation pressure, fracture gradients and formation stability • In cases where no wells have been drilled previously these pressure are estimated from geophysical data collected while prospecting.
  • 8. Decide target depth • Before any drilling activity can begin, the target depth of the well to be drilled is decided. • This is because an oil well is usually drilled in three or less section known as phases if there is no hole problem. • This is to ensure optimum use of men and materials
  • 9. Decide hole geometry • An oil well is usually drilled in phases – each succeeding phase being smaller in diameter than the preceding phase. • The exact configuration of these phases i.e the hole diameter and the exact depth to which each phase will be drilled is decided. • The casing sizes are based on the hole sizes
  • 10. Decide casing setting depth • Once a particular diameter hole is drilled it is cased and cemented to prevent formation collapse. • The formation strength, the fracture gradient and the possible formation pressure is considered to determine when it is safe to set casing to prevent formation breakdown or influx of formation fluid to the well bore.
  • 11. Decide cement plan • Cementation is done to hold the casing in place. • This helps to hold the casing by forming bond between the formation wall and the casing. • To do this, the volume of slurry required to fill up the annulus has to be calculated, the type of cement to be used, the cement additives, the composition of the cement slurry must be well planed and documented.
  • 12. Mud program • Drilling fluids are required to drill an oil well. • Details about the type of mud, the mud properties and the various mud additives to be used for drilling the well are laid out in mud program.
  • 13. Design drilling program • Detailed specifications about the various drilling parameters at various depths like weight on bit (WOB), rotation per minute (RPM), pump pressure and flow rate of the drilling mud are taken into consideration in well plan. • In addition the type of drilling whether vertical or deviated is also specified in the drilling plan
  • 14. Design bit program • Specification of the various drilling bits to be used at various depths are mentioned here. • The type of bits to be used, the size of bit & nozzle sizes to be used and the various hydraulic parameters to be maintained are also discussed.
  • 15. Design formation evaluation program • The process of identification, location and appraisal of formations containing oil, by the well site geologist as the drilling continues is known as formation evaluation. • Formation evaluation is done with the help of logging techniques such as wire line logging, mud logging, coring & cutting analysis. • Details of the kinds of logging to be done, their frequency and depths to which electric logs will be run are mentioned in the formation
  • 16. Completion plan • A general idea about the method to be used to produce the well after completion of drilling is itemized in the completion plan. • Completion can be open hole, cased hole with single tubing or cased hole with multiple tubing’s and packers.
  • 17. Testing program • The kind of testing which will be done upon completion of drilling is specified in testing plan. • The type of testing to be done and at which depth, may be open hole testing or cased hole, it must be specified here.
  • 18. Select rig • The rig selection is primarily based upon the total depth to be drilled. • This is because the drilling capacity of a rig will depend upon its load carrying capacity as it will have to lift a heavier load to drill deeper. • Thus to drill a deeper hole a higher capacity rig is used
  • 19. Project drilling time • Based on the various factors, the total time required to drill the well and complete it are estimated. • In addition to the total time, a detailed break up of drilling days versus depth and the time required for various activities like casing e.t.c is also made. • This estimate is generally very accurate and drilling is usually completed according to plan
  • 20. Estimate costs. • An accurate estimate of the cost of drilling the well is made. • These costs falls into two broad categories, for consumables and for services required. • The cost of services required is usually dependent on the total number of days required to drill the well. • The amount of consumables will depend on the target depth of the well.
  • 21. Drilling contract • For effective drilling operation both in terms of cost, safety and timeliness, a detail contract is entered into between the operator and the drilling contractor. • This is aimed at drilling usable hole for the operator efficiently, safely and economically. • Different types of contract are available depending on the agreement between the operator and the drilling contractor
  • 22. Day rate • The rentals for rig and personnel charges are based on the number of days that the rig is on site irrespective of the number of meters/feet drilled per day. Footage/Meterage rate • The rental for rig is based on the number of meters/feet that the rig drills at a particular location, irrespective of the number of days on location.
  • 23. Turnkey • Here all the services required to drill and complete a well are to the drilling company. • That is the sum total of the cost required to drill the well to TD is paid the contractor irrespective of number of days spent on location and the number of feet/meter drilled per day. • This contract type is more popular as it increases the efficiency of drilling company.
  • 24. Types of oil wells drilled.  Exploration Well - A well drilled for the purpose of ascertaining or confirmation of oil accumulation.  Appraisal wells are drilled to determine the extent of the reservoir, so as to know volume of the oil reserve.  Development wells (Infill drilling or Well) – This is a well drilled to optimize oil production form a given reservoir or field.
  • 25.  Directional Well. This is the science of directing a wellbore along a predetermined trajectory to intersect a designated sub – surface target.  Horizontal Well drilling is the science directing a wellbore along a predetermine trajectory usually at an angle of 900 to the vertical to intersect a designated sub- surface target
  • 26. TYPES OF DRILLING RIGS It is always desired to drill in different geographic and climatic environment. However, the basic drilling operation remains essentially the same regardless of the types of rig used or the environment where the rig is used.  LAND LOCATION (ON SHORE)  land rig is used which consist of derrick or mast, substructure, mud pit, drillers cabin, prime movers, hoisting equipment, rotating equipment, circulating equipment and crew residential cabin.
  • 27. WATER DRILLING EQUIPMENT (MODU) • Inland water equipment – Inland water drilling includes swamp, dredged marsh, bay and lagoon locations where water is relatively shallow and protected from appreciable wave action. • Submersible (Inland Barge) drilling barge is used. Inland barges are designed for drilling in 10 – 20 ft of water. • Drilling in deeper water with submersible barge is accomplished by construction of a shell gravel fill for the barge to rest on.
  • 28. Jack – up rig  May be used from 50 ft to 350 ft of water.  The cost of such installation is enormous, but may be quite economical on a per well basis, since numerous wells may be directionally drilled from its deck.  They are very useful in development drilling and poorly adapted to exploratory work
  • 29. Jack – up rig
  • 30. Semi submersible Rig  These types of rig are often refers to as semi for short.  They are floating barge.  They use anchors on the sea floor to keep the rig stationary.  They can be used in water up to 7000ft (2100m).  Water is allowed to enter the barge so as to lower the rig to the sea level for drilling.
  • 32. DRILLING SHIP (Floater)  This is a large self contained ship, which contains substructures, drawworks, rotary table, engines, mud pits, dry mud, chemicals etc, pipe racks, cementing equipment, fuel and water and crew quarters.  The ship can operate in any weather short of hurricane. It can be used for a deep offshore drilling and in remote areas.  It uses dynamic positioning to keep them on station (it uses computer controlled motors or thruster and sensors)
  • 34. THE OIL COMPANY COMPANY MAN SAFETY ENGINEER MARINE CREW WELLSITE GEOLOGIST TOOL PUSHER DRILLER DERRICK MAN ROUGHNECK ROASTABOUT MUD ENGINEER CEMENT ENGINEER WELL TESTING OPERATOR CASING ENGINEER DIRECTIONAL DRILLER MUD ENGINEER CORING ENGINEER MUD LOGGING ELECTRIC LOGGING FIGURE SHOWING THE INTERDEPENDENCY OF VARIOUS PERSONNEL INVOLVED IN DRILLING OPERATION DRILLING RIG PERSONNEL
  • 35. Crews may consist of four, five, six, or more individual depending on the size and service rating of the rig itself. TOOLPUSHER The Tool pusher – sometimes called the rig superintendent or rig manager – is the man in charge of the rig and overall drilling operations. Driller - is directly in charge of drilling activities; he supervises other workers in the rig. He is next to the tool pusher.
  • 36. DRILLING RIG PERSONNEL  Derrick man or assistant driller – he is next to the driller, stays at the monkey board to control the pipe during tripping.  After tripping he monitors the mud.  Floor man or roughneck – they are in charge of making up and breaking out drill pipe while drilling or tripping.  Motorman, Mechanics, Crane operator and roustabout e.t.c.
  • 37. MAJOR COMPONENT OF DRILLING RIG  Power system (prime mover)  Hoisting (Drawworks, Blocks and drilling line, Derrick)  Rotary system (Swivel, (Kelly, Rotary Table) Top Drive system , Drill pipe, Drill collar & Bits)  Circulating system (Drilling fluid, Mud pumps, Mud tanks, The mud cycle (desilter, dessander, degasser))  Well Control system (Blowout Preventer, Accumulator, Diverter)
  • 38.
  • 39. PRIME MOVERS  Prime mover provide power for the rig.  It is usually an internal combustion engine. POWER  1 hp = 33,000ft – lb/min. The amount of power required for drilling varies with the job, but most rigs require from 1,000 to 3,000hp, usually provided by two or more engines.  Shallow or moderate – depth rigs need from 500 to 1,000hp for hoisting and circulating, heavy-duty rig may require 3,000 hp or more. The power requirements for rig auxiliaries such as lighting and air conditioning may be from 100 to 500 hp.  Power Transmission: A rig may have a mechanical drive or an electric drive (which may be an AC – DC drive or DC – DC drive).
  • 40. HOISTING SYSTEM Derrick or Mast  Derricks and portable masts provide the clearance and structural support necessary for raising and lowering drill pipe, casing, rod strings, etc., during drilling and servicing operations.  The derrick or mast must be designed to safely carry all loads that are likely to be used during the structure’s life.  Wind load and compressive load.  Wind load is given as: P = 0.00338 (V2)(Ch,)(Cs) P = pressure in. lb/ft2 V = wind velocity in knots Ch = height coefficient Cs = shape coefficient (1.25 for derrick)  Derrick load* = 1.5(Wh + Wc + Wt + 4FL)
  • 41. HOISTING SYSTEM DRAWWORKS  The drawworks, is a big heavy piece of machinery that consists of a revolving drum around which the wire rope, called the drilling line is spooled or reeved.  It also has a cat shaft, a kind of axle that crosses through the drawworks that has a revolving drum (called a cathead spool) on either end or two special catheads.  Several other shafts, clutches and chain and gear drives facilitate speed and direction changes. COMPONENTS PARTS  Drillers Console, brake lever, drum shaft, sprocket, gears and chains. It also contains drum brake and equalizers, cat shafts with cat heads.
  • 42. Functions of Drawworks  Transmit power from the prime mover to its hoisting drum to lift drill string, casing string or tubing string or to pull in excess of these string loads to free stuck pipe.  Transmit power to the catheads for breaking out and making up drill string, casing and tubing string.  Transmit power from the prime movers to the rotary drive sprocket to drive the rotary table.  The hoist contains brake systems which enable the driller to easily control a load of thousands of pound of drill pipe or casing. There may be at least 2 types of brake system.  1) The mechanical and (2) Hydraulic or hydrodynamic or electric
  • 43. The drawworks on the rig floor
  • 44. BLOCKS AND DRILLING LINE  The drilling line supports the entire drilling assembly by means of pulley – style devices and grasping implements, which are collectively called the overhead tools.  Included among these are the crown block, traveling block, the hook, drilling line and the elevators. CROWN BLOCK  The crown block is an assembly of sheaves mounted on beams at the top of the derrick. Most crown block has 4 to 7 (seven) sheaves which may be as large as 5 – feet in diameter mounted in line on a common centre pin.
  • 46. TRAVELING BLOCK • The traveling block moves between an up and a down position on the line. • It carries the hook that support drill string when drilling and the elevator bail that holds the elevator when tripping in or out of the hole. • Selecting a block for a certain rig or for a certain job depends on the block load capacity in tons
  • 47. HOOK  The hook is a large joining device suspended from the traveling block to grip the various piece of equipment needed in drilling and in making trips.  It rotate on bearing in its supporting housing and can be locked into many as twelve different position.  The hook has a safety latch for the swivel and locking arms or link ears at both sides for elevator – bail attachment.
  • 49. DRILLING LINE  Drilling lines are made of steel wires that are made into strands and the strands into rope in action similar to braiding.  The outer strands are laid spirally around a central core.  The wire rope generally ranges from 1 1/8 to 11/2 inches  The important things to watch out for to prevent wear to drilling line are: the tread diameter of the block sheaves, the critical points, groove radius, fleet angle and prevent sudden loading.
  • 50. ROTATING SYSTEM  The rotating equipment from top to bottom consists of the swivel, Top Drive System (TDS) (the Kelly), the rotary table, the drill stem and the bit.  The drill stem is the assembly of the swivel and the bit (i.e. drill pipe and drill collars, stabilizer e.t.c.) SWIVEL  Swivel in a device joining two parts so that one or both can pivot freely. It is attached to the traveling block by a large bail. It may rotate more than 200rpm. FUNCTION OF SWIVEL  It supports the weight of the drill stem  It allows the drill stem to rotate  It provides a pressure – Tight seal and passage way for the drilling mud to be pumped down the inside of the drill stem  Pronounced on a Kelly rig.
  • 51. KELLY  The Kelly is a square, hexagonal or triangular piece of pipe, usually about 40 ft long, which serves the purpose of transforming the rotating motion of the rotating table to the drill string FUNCTION OF KELLY  It serve as a passageway for drilling fluid on its way into the drill pipe .  It transmits the rotating movement to the drill pipe and bit.  It may serve as well control equipment through upper and lower Kelly cock.  The Kelly fits into a corresponding square or hexagonal opening in a device called a Kelly bushing or drive bushing. The Kelly bushing fits into a part of the rotary table called the master bushing or rotates and as the Kelly rotates, the drill string and bit rotate.
  • 52. THE ROTARY TABLE The function of rotary table is to: • To turn and rotate the Kelly (or any equipment attached to it) • To support the weight of the drill string or the casing during make up or break out • When drilling is going on, the rotating turns to the right or clockwise. • When the pipe is pulled from the well bore, the rotary table supports the string on slip during intervals when pipe is not being suspended from hook. • The rotary table rotates through a working range of 40 – 50 to 200 revolutions per minute (rpm). As the hole deepens the Kelly descends through the bushings, which are mounted in the table openings.
  • 54. TOP DRIVE SYSTEM (TDS) • It provides rotation for the drill string instead of rotary table in Kelly rig. • It consists of gear box, one or two hydraulic motors, a pipe handler or grabber which includes torque arrestor. • It also has guide and torque track which terminates 7-9 feet above drill floor and elevator links including elevator. • The speed can be up to 600 rpm.
  • 55.
  • 56. DRILL STRING  The drill string is made up of the drill pipe and special heavy – walled pipe called drill collars. DRILL PIPE  Each length of drill pipe is about 30 ft long and is called a joint of pipe.  Drill pipe is attached to Kelly at the top (on a Kelly rig) but connects to the TDS and to the drill collar (HWDP) at the bottom. Function of Drill Pipe  Permit rotation  Allow fluid passage to the bit.  Provide necessary length of the well drilled Each end of each point is threaded.  The end of the joint with interior threads is known as the box, and the end of the joint into the exterior threads is called a pin.  The joints are welded to the body of the pipe.
  • 57. DRILL COLLAR  These are heavy walled pipe of small diameter steel tubes, like drill pipes, through which mud can be pumped. ROUNDED OR SQUARE (Drill collars)  Drill collars are about 30ft long and unlike the drill pipe that has tool joints welded on, they have the boxes and pins cut into them. FUNCTION OF DRILL COLLAR  To transfer rotary action to the bit  To allow passage for drilling mud  To put weight on the bit  To provide good stabilization for the bit to drill a straight hole.
  • 58. Rotating equipment.  Heavy wall drill pipe (HWDP) - consist of heavy wall tubes with an upset in the middle, called the center wear pad.  It is a transition between the drill collar (DC) and the drill pipe (DP) to make the crossover gradual.  Stabilizers. These are drill string components with blades that protrude from the body.  They are usually almost the same diameter as the bit and are located in a drill string at various points in the drill collars of the BHA, including just above the bit for directional/deviated hole and far up or in the middle for vertical hole drilling.
  • 59. SUBS  These are short sections of drill collars materials about two feet (2 ft) or longer, which provides crossovers between different diameters and types of threaded connection.  They are available in different connection configuration such as: box / box, pin / pin, pin / box and box / pin subs  Crossover subs  Float subs – a non – return valve run just above the bit (to prevent kick through drill string)  Dart sub – a landing sub for a drop in and pump – down back pressure valve.  Its function is to prevent kick through drill string like float sub.  Bent sub.
  • 60. BITS  The drilling bit is attached to the drill collar through the bit sub. This is the part of the rotary system that does the actual hole making.  THE DRAG e.g. FISH TAIL.  it does not have a moving pact.  It drills by shoveling action against the formation.  The water course opening is directed against its blade so that it can remove any shale that may be attached to the cutting surface.  It is used mainly to drill a soft formation, especially at a shallow depth. ROLLER CONE BIT  It has cone – shaped steel devices called cones that are free to turn as the bit rotates. Most bits have 3-cones, but some have 2 and some have 4 cones
  • 61. There are two types of Roller cone bits: • The steel tooth bit and (b) Tungsten – carbide inserted bit • All bits have passage drilled through them to permit drilling fluid to exist. • Jet nozzle opening. • They can be used for both soft, medium hard and hard formation depending on its design. • Roller bearing and journal bearing.
  • 63. DIAMOND BITS  Since diamonds are so hard, diamond bits are specially suited for drilling hard rock formations but may also be used effectively on soft formation.  A PCD (polycrystalline diamond bit) is also a type of drag bit.  A cylindrical Coring bit is also available with diamond studded.
  • 64. A PDC bit for soft formation
  • 65. CIRCULATING SYSTEM  For the rotary drilling system to function, fluid must be circulated downward through the drill stem, around the bit and upward in the annular space between the drill stem and the wall of the hole or the casing. (The circulation route). THE DRILLING MUD (FLUID)  The term “drilling fluid” includes air, gas, water and mud.  The term “mud” refers to a suspension of solids in water or oil or of solids and droplets of one of these liquids (emulsion) dispersed in the other. The mixture of clay (Solid bentonite) and water or oil is a mud. The drilling mud consist of phases  i. The liquid phase (water or oil) (may be fresh or salt water)  ii. The colloidal fraction (bentonite or Wyoming clay)  iii. The inert fraction (barite, weighting material etc)
  • 66. Functions Of Drilling Mud To transport bit cutting to the surface To clean the bottom of the hole (bit) To cool and lubricate the bit and drill stem To support the walls of the wellbore To prevent entry of formation fluids into the well i.e. control subsurface pressure. To suspend cutting when circulation is stopped.
  • 67. THE MUD PUMP  The function of the mud pump is to circulate the drilling fluid from the tank, through the drill stem, to the bit (where hydraulic power is expended for jetting), back up the annulus and back to the tank.  The mud pumps are either Duplex, double – acting pumps or triplex pump.  The term “duplex” refers to the number of pistons (2) and term “ double – acting” denotes that each side of piston does work. Pulsating discharge and high pressure.  Triplex has 3 pistons and single acting. High flow with smooth discharge.
  • 68. Schematic valve operations for double acting duplex pump . Piston Piston rod P2 Discharge P1 inlet or suction
  • 69. Pressure control system  Pressure control system includes Blowout Preventers (BOP), diverters, choke and kill line and accumulator unit.  Types of Blowout Preventer (BOP) (Annular Preventer and Ram Preventer)  Ram preventer has three types of rams (pipe ram, blind ram and shear ram). Functions of BOP  To close the wellbore and contain pressures  Allow wellbore fluids to be control vented.  Allow pumping into the well (when usual means are not available)  Allow tripping of drill pipe into and out of the hole
  • 70. CASING  Casing is a strong cylinder steel pipe used in an oil well to ensure a pressure tight connection from the surface to the oil or gas reservoir. FUNCTIONS OF CASING  To prevent cave-in or washout of the hole  To prevent contamination of fresh water sands by fluids from lower zone  To exclude water from the producing formations  To confine production to the well bore  To provide a means of controlling well pressure  To permit selective production of the pay zone  To furnish a permanent borehole of precisely known diameter
  • 71. TYPES OF CASING Drive Pipe  It is used to prevent shallow formation damage and collapse.  It also provide support and passageway for the conductor casing (Not always used especially in a consolidated formation).  Installed by driving the pipe to a point of refusal. Off shore consideration  Slip joint takes care of heaving up and down of the water body  Slip joint is connected to the marine riser at the bottom and the vessel body.  Flex Joints. A flex joint is installed between the lower end of the riser and the BOP stack.  This joint essentially acts as a pinned connection to minimize bending stresses in the riser as the drilling vessel is moved by wind, wave and current action.
  • 73. TYPES OF CASING CONDUCTOR CASING  Conductor pipe is used as a channel to raise the circulating fluid high enough to return to the pit.  It prevents erosion of the hole around the base of the rig.  It protects the subsequent casing strings from corrosion and may be used to support some of the wellhead load on location where ground support is not enough.  May be set 300ft or more. SURFACE CASING  Surface casing is set deep enough to protect the well from cave- in and washout of loose formations that are often encountered near the surface.  It provides a point of attachment for casing head and other fittings that will be left on the completed well.  Surface casing is usually set from 300ft to 4000ft.
  • 74. INTERMEDIATE CASING  The intermediate casing is to protect the hole (called production or salt casing).  It is used to seal off weak zones that may rupture with heavy mud usually needed for deepening a well. PRODUCTION CASING  This string of casing serves to isolate the producing reservoir from undesirable fluids in the producing formation and from other zones penetrated by the well bore.  It is the protective housing for the tubing and other equipment in a well. LINER STRING  A liner is an abbreviated string of casing used to case open hole below existing casing.  Production liners are sometimes suspended in the well without cementing.
  • 75. FORCES ON CASING • The major forces acting on casing are: • Tension: this is a downward pull of the weight of the casing string on the pipe body and on the coupling created at the top of the casing string Burst • Burst pressure occurs when the pipes internal pressure is greater than the external pressure Collapse • This is an unbalanced external pressure imposed on pipe.
  • 76. PRIMARY CEMENTING  Primary cementing is the process of mixing and placing cement slurry in the annular space between a string of casing and another casing or casing and the open hole.  The cement sets, bonding the pipe to the formation.  Cement slurry is the mixture of dry cement with water and necessary additives to condition the slurry to suit the hole characteristics.
  • 77. CONDUCTOR PIPE 36” / 300’ SURFACE CASING 20” INTERMEDIATE CASING 13 3/8/ 5000’ PRODUCTION CASING 95/8” LINER STRING 7” Fig. 12.0 WELL SCHEMATICS SHOWING CASING STRINGS ASSEMBLY
  • 78. CEMENTING TOOLS  Cementing head, top plug, bottom plug, float collar, centralizer, Guide shoe, Scratchers, cement pump, cement mixer. Guide Shoe  A guide shoe is a round-nosed device installed on the first joint of casing with thread – locking compound.  It has opening in the bottom to allow drilling mud to enter the casing as it is lowered.  It is always used.  There are three types of guide shoes:  1) Plain guide shoe, 2) The combination of float and guide shoe, 3) Automatic fill-up guide shoe.
  • 79. Float Collar  This is similar to float shoe, it permits the casing to float into the hole.  The float collar may be installed on top of the first joint or on top of the second or third joint to go into the hole.  Most operators employ a float collar at a distance of one or more joints above the casing shoe in order to provide space inside the casing for contaminated cement.  Provide a stop point for bottom plug
  • 80.  Centralizers  These are steel metals used to keep the casing pipe away from the borehole wall.  They must be spaced close together enough to prevent the casing from contacting the formation wall even in a deviated hole. They are used to:  Ensure a reasonably uniform distribution of cement around the pipe  Obtain a complete seal between the casing and the formation. Cement Scratchers  These are mechanical wall cleaning devices attached to casing.  They abrade the hole when worked by reciprocating or rotating the casing string  Ensure good bonding between the casing and the formation.
  • 81. Bottom plug (Wiper plug)  The bottom plug is a cylindrical hollow molded rubber body.  It contains diaphragm at the top which rupture to allow cement slurry to flow through and also has wipers protruding from its side that removes mud.  It is the first plug to go into the casing from the cementing head.  It wipes mud off the inside of the casing and keeps the mud separated from the cement. Top Plug (Wiper plug).  The top plug is a solid cylindrical core with four wipers protruding from its sides.  The top plug follows the cement into the casing and wipes cement off the inside wall of the casing.  It also prevents the mixing together of cement and the displacement fluid behind the cement.  This plug is solid. When it seats or bumps on the bottom plug at the float collar, pump pressure increases since no fluid can get pass the top plug.
  • 82. Cement Head.  This house the wiper plugs and also the cementing line is attached to it.  The cement flows into the casing through the well head and also provides a channel through which the drilling mud in the annulus flows to the surface.
  • 83. A centralizer, scratchers, guide shoe and float collar.
  • 84. DRILLING PROBLEMS  A lot of hole problems are encountered and may be avoided or overcome by proper control of mud properties. These are:  Salt section hole enlargement  Heaving shale problems  Blowouts  Lost circulation  Formation damage  Key seating  Bit balling
  • 85. HOLE EROSION CAUSE  Hole erosion results from the hydraulic impact on formations with poor inter-grain cementation.  Generally it is caused by turbulent fluid flow in the annulus or excessive circulation in one place with the bit off bottom. Effect  The annular fluid velocity will be reduced in enlarged hole sections. If the drilling fluid is not highly pseudoplastic, the cuttings can concentrate in this area.  Eventually they may form a 'mud ring' or ball of agglomerated cuttings, which in severe cases can lead to hole pack-off and stuck pipe.  Good cementing practice requires turbulent flow to ensure proper drilling fluid removal.  Large washed out sections may cause the flow to become laminar and poor drilling fluid removal.
  • 86. PREVENTION  -Keep the flow regime laminar, where possible. Maintain highly pseudoplastic rheology  -Low shear rate viscosity along with the reduced flow rate requirements this makes an excellent fluid for unconsolidated formations.  -In silty formations examine the possibility of water sensitive clays causing further destabilization. If suspected, test with small treatments of inhibiting chemicals or polymers.
  • 87. SALT SECTION HOLE ENLARGEMENT  When salt domes are penetrated, they dissolved, eroded, thus causes an excessive hole enlargement, which in turn may be a source of future trouble and expense  In case of drill string failure, the enlarged hole makes fishing operation (attempts to retrieve the drill string) exceeding difficult  Larger mud volumes are required to fill the system hence treating cost are higher  Large cement volumes are required for casing operation if fill – up through the section is to be attained Solution.  The principal means of avoiding these problems is to prepare a salt saturated mud system prior to drilling the salt, thus avoiding the dissolving effect.
  • 88. HEAVING SHALE PROBLEMS  Some areas are characterized by shale sections containing bentonite or other hydrated clays, which continually absorb water, swell and slough into the hole.  This often occurs in the younger formations in the upper hole sections. It is the result of water imbibition by a smectitic shale.  They can cause pipe sticking, excessive solids build up in the mud and the hole bridging are typical resultant problems.  The annular diameter is reduced. The drill string, logging tools and casing may not easily pass through.  Increased annular friction pressure losses may raise the ECD above the fracture pressure for a lower zone. .  Sloughing shale can also be caused by brittle failure resulting from differential rock stress.
  • 89. Heaving shale. This can be due to tectonic activity or deviation of the well bore from vertical.
  • 90. Hole collapse by caving in The rock can fail in either tension or compression depending upon the orientation of the stresses to the wellbore wall
  • 91. SOLUTION TO HEAVING SHALE  Changing mud system to inhibitive type e.g. lime, gypsum which reduces tendency of the mud to hydrate water sensitive clays  Changing to oil emulsion mud or oil base mud  Increase circulation rate for rapid removal of particles  Maintaining a positive pressure overbalance against the formation pressure will help to hold the failed rock pieces in place
  • 92. DIFFRENTIAL PRESSURE STICKING  This is the force that holds pipe against the wall of the hole, due to the differential between formation pressure and hydrostatic pressure  Circulation is not hindered. For differential sticking to occur the following criteria are required:  Hydrostatic pressure must exceed formation pressure.  A zone of permeability must exist, over which a thick filter cake has been deposited.  There must be contact between the pipe and the filter cake
  • 94. KEY- SEATING  A key seat results when drill pipe under tension wears a slot into the wall of the hole during drilling and tripping operations.  It often occurs when drilling a directional well.  The slot diameter is usually the same as the diameter of the drill pipe tool joints.  The drill collars are therefore most likely to get jammed in a key seat when pulling out of hole. Recognizing key-seating  Key seating is indicated by an increasing over pull, normally during tripping.  Here again the circulation is not impeded after the string has become stuck.
  • 95. Key seating The development of a key seat
  • 96. BLOWOUTS  A blowout occurs when formation pressure exceed the mud (hydrostatic) pressure which allows the formation fluid to flow out of the hole.  This is one of the most expensive and highly feared hazards of drilling Blowout may occur due to:  Swabbing i.e. pipe pulling (suction) out of the hole too rapid  When a zone of high pressure (gas zone) is encountered Solution.  The solution is to drill with proper mud density to overcome the encountered subsurface pressure
  • 97. LOST CIRCULATION Lost circulation is defined as the loss of substantial quantity of mud or whole mud to an encountered formation.  This is shown by complete or partial loss of returns (annular mud return)  Drop in annular mud volume may also cause kick Types of formation to which circulation may be lost are:  Coarsely permeable rocks e.g. gravels, reef, and irregular limestones  Faulted, jointed and fissured formations such as  Those with naturally occurring fractures  Those in which the fractures are induced or caused by column pressures  Cavernous and open fissured formations Prevention  Minimum overbalance of hydrostatic head, plus ECD.  Cure  Cut down the pump rate , reduce the overbalance , block the permeable channels by pumping LCM.
  • 98.
  • 99. FORMATION DAMAGE  Formation damage is caused by the invasion of foreign fluids and / or solids into the exposed section adjacent to the well bore.  Generally, the drilling mud is the main source of such contaminants.  Fluids used in stimulation treatment (acidizing, hydraulic fracturing etc) may also have some undesirable effects, which partially nullify their beneficial actions.  This damage when it occurs in the pay zone hinders or prevents the flow of oil or reservoir fluid into the well bore or production tubing. JAMMING A NEW BIT  An undergauge hole is a section of a hole with a smaller diameter than the diameter of the new bit used to drill ahead.  The most common cause of under-gauged holes is gauge wear on the previous bit run
  • 100. DRILLING LINE SERVICE  (Ton – miles of Drilling line) uses Lb-ft  The amount of wear a drilling line suffers is closely related to the amount of work it helps accomplish.  Ton – miles of service are accumulated on:  round trips ,  in drilling,  coring,  reaming,  fishing and  running casing – in fact, during any operation that entails putting any load on the drilling line.  Tables are available to assist in calculating drilling line service
  • 101. Fish and fishing operation • Fishing is the act of retrieving any lost or stuck tool from the well bore. Tools used includes: • Free point detector • String shot back off • Jet, chemical cutters • Wash over pipe • Overshot • Spears • Jars and accelerators • Impression block • Tapered tap e.t.c.
  • 102. DOWN HOLE MOTORS Turbine Motors  The activating drilling mud or freshwater is pumped at high velocity through the motor section, which, because of the vane angle of each rotor and stator (which is a stage), causes the rotor to rotate the shaft of the motor.  The kinetic energy of the flowing drilling mud is converted through these rotor and stator stages into mechanical rotational energy.  The rotors are forced to turn, causing the bit to rotate.  The major advantage of turbine is that they can operate at higher temperature than the PDMs.
  • 103. Positive Displacement Motors  A positive displacement motor (PDM) also drive the drill bit independent of the drill string rotation.  Soft, medium and hard rock formations can be drilled with a positive displacement motor using nearly any type of rock bit.  Rather moderate flow rates and pressures are required to operate the positive displacement motor.  Thus, most surface pump systems can be used to operate these downhole motors.  Rotary speed of the positive displacement motor is directly proportional to flow rate.  Torque is directly proportional to pressure. Thus, normal surface instruments can be used to monitor the operation of the motor downhole.  High torques and low speeds are obtainable with certain positive displacement motor designs, particularly, the higher lobe profiles.
  • 104. DIRECTIONAL DRILLING  The common method of drilling a directional well is to use a downhole motor with a bent sub.  The bent sub is directly placed above the motor.  It is the bent sub which makes the deflection assembly, its lower thread is inclined 10 to 30 from the axis of sub body.  Downhole and the bent sub assembly can be used for kicking off wells, for runs correction and for side tracking.  Whipstocks (standard removable & permanent casing whipstock) can be used to kick off well by applying weight to set it and shear its pin.  But may lead to severe dogleg and lots of rig time in tripping and opening the rat hole.
  • 105. DIRECTIONAL DRILLING • Jetting (or badgering) is a technique used to deviate wellbore in soft formation. • A special jet bit is used and the formation must be soft enough to erode by the action of drilling fluid. • Also adequate rig hydraulic horsepower must be available to erode the formation.
  • 106. conclusion We have seen different types of:  Rigs  Drilling techniques (onshore & offshore)  Vertical and directional well  Hole problems and possible solutions  Fishing operations Let us complete the well.