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THE CASING STRING
Manufacture of Casing String
The three basic processes of manufacture casing are: (1) Seamless Process, (2) Electric resistance Welding (3) Electric flash
elding
Billet
Billet
!andrel Process
Mandrel Mill
Mandrel Mill
3 Roll Reducer
3 Roll Reducer Hot Finished Seamless i!e
Hot Finished Seamless i!e
Hot Coil
Hot Coil
Electric "esistance
#$lash Welding
ER"#EF" i!es
ER"#EF" i!es
The heated billet is introduced to a mill,
here it is gripped b% to obli&uel%
oriented rolls that rotate and ad'ance
the billet into a central piercing plug
The pierced billet is process through
the plug mills to produce uniform
dimension and roundness
The electric resistance elding
continuousl% maes casing from coiled
sheet stoc that is fed into the
machine, formed and elded b% an
electric arc
Electric flash elding techni&ue
processes a sheet b% cutting it to the
desired dimension, simultaneousl%
forming the tube and flashing and
pressing the to edges together to
mae the eld
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THE CASING STRING
Standardi$ation of Casing
The *merican Petroleum +nstitute (*P+) has de'eloped
standards for casing and other tubular goods that
ha'e been accepted internationall% b% the petroleumproducing industr% -asing is defined as tubular pipe
ith a range of ./ of 0 to 2 in
*mong the properties included in the *P+ standards
for both pipe and couplings are strength, ph%sical
dimensions, and &ualit%control test procedures *P+
has adopted the strength characteristics of the pipe
The grade code consists of a letter folloed b% a
number
The letter designation in the *P+ grade as selected
arbitraril% to pro'ide a uni&ue designation for each
grade of casing adopted in the standards The number
designates the minimum %ield strength of the steel in
thousands of psi
AI Grade%ield Strength
&'si()TS&'si(
*+,-. ,-./. ,0./.T+1- 1-/. ,.-/.
H+2. 2./. 0./.
+-- --/. 4-/.
5+-- --/. 1-/.
C+4- 4-/. 1-/.
6+7. 7./. 1-/.
N+7. 7./. ,../.
C+1. 1./. ,../.
C+1- 1-/. ,.-/.
M+0- 0-/. 7-/.
+,.- ,.-/. ,8./.
+,,. ,,./. ,8-/.
9+,8- ,8-/. ,3-/.B 3-/. 0./.
:+28 28/. 0./.
:+20 20/. 03/.
:+-8 -8/. 00/.
:+-0 -0/. 4,/.
:+0. 0./. 4-/.
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THE CASING STRING
Casing and Tu;ing Threads
earl% all tubular goods used in completing a ell
come in 4oints that 'ar% from 3 to 0 ft in length
5oints ha'e threads machined into their ends hichser'e to hold the string together /ifferent t%pes of
tubular goods ha'e threads hich differ in si6e, shape,
and in the a% the% seal and mae up to hold
pressure
Since 1728, threads ha'e been regulated b% the
*merican Petroleum +nstitute (*P+) There are fi'e
important areas of thread t%pes, selection, and care
-asing Threads
-asing Threads
Tubing Threads
Tubing Threads
!aeup Tor&ue Selection
!aeup Tor&ue Selection
Thread -are
Thread -are
Thread Selection
Thread Selection
The most common threadsin use toda% for casingconnections are:
8 "ound Thread (ST-#9T-)
8 "ound Thread (ST-#9T-)
Etreme line (E9)
Etreme line (E9)
;uttress (;T-)
;uttress (;T-)
Eight Round Thread
Eight Round Thread
Buttress
Buttress
E
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THE CASING STRING
Casing and Tu;ing Threads
The tubing or production string pro'ides a flo path to
the surface for produced fluids Tubing is not
cemented into place as is casing Therefore, thethreads on tubing 4oints and collars are designed to
ithstand great tensile loads and internal pressures
9ie casing 4oints, tubing has threads on both ends
To t%pes of tubing threads are:
Eternal
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THE CASING STRING
Mar'ings and Color Identification
*P+ -T Spec
*P+ -T Spec
*P+1-
T=rades
*P+1-T=rades
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THE CASING STRING
ur!ose of Casing String
*t a certain stage during the drilling of oil and gas
ells it becomes necessar% to line the alls of a
borehole ith casing -asing ser'es numerouspurposes during the drilling and production histor% of
oil and gas ells, these include:
>eeping the hole open b% pre'enting the ea formations
from collapsing
Ser'ing as a high strength flo conduit to surface for both
drilling and production fluids
Protecting the freshaterbearing formations from
contamination b% drilling and production fluids
Pro'iding a suitable support for ellhead e&uipment and
bloout pre'enters for controlling subsurface pressure and
for the installation of tubing and subsurface e&uipment
*lloing isolated communication ith selecti'el% perforated
formations of interestof interest
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THE CASING STRING
T=!es of Casing
-asing is usuall% di'ided into fi'e basic t%pes
-onductor
Surface
+ntermediate
Production
9iner
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THE CASING STRING
T=!es of Casing
-onductor
-onductor pipe or dri'e pipe if it is hammerdri'en to
depth, is the first string of casing to be used The
setting depth can 'ar% from 1 ft to around 3 ft The
normal si6e range for conductor pipe is from 1? to 3?
inches (outside diameter) The conductor pipe must be
large enough to allo the other casing strings to be
run through it Purposes of conductor pipe are to:
"aise the le'el of circulating fluid so that fluid returns arepossible
Pre'ent ashouts in the near surface, normall%
unconsolidated formations
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THE CASING STRING
The amount of surface casing used ill depend on the
depth of the unconsolidated formations Surface
casing is usuall% set in the first competent formation
ormal si6e for surface casing is beteen 2 inch
and 133#8 inch (outside diameter) Since
temperature, pressure and corrosi'e fluids tend to
increase ith depth, different grades of casing ill be
re&uired to handle the different ell conditions
Purposes of surface casing are to:
Protect fresh ater formations
Seal off unconsolidated formations and lost circulation 6ones
Surface
Pro'ide a place to install the ;.P@s
Protect AbuildB sections on de'iated ells
Pro'ide for a sufficient AleaoffB test to be conducted
T=!es of Casing
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THE CASING STRING
+ntermediate
+ntermediate casing is set after surface casing,
normall% to seal off a problem formation The si6e of
intermediate casing, ill depend on the si6e of the
surface casing and the grade re&uired to ithstand the
subsurface conditions ormal si6es are beteen 7
#8 and 13 3#8 inch (outside diameter)
Production
Production casing is usuall% the last full string of pipe
set in a ell These strings are run to isolate producing
formations and pro'ide for selecti'e production in
multi6one production areas The si6e of production
casing ill depend on the epected production rate,
the higher the barrel per da% production rate, the
larger the inside diameter of the pipe -ommon si6es
are beteen 3 and C inch (outside diameter)
T=!es of Casing
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THE CASING STRING
9iner
* liner is a string of casing that does not reach the
surface The% are usuall% AhungB (attached to the
intermediate casing using an arrangement of
pacers and slips) from the base of the intermediate
casing and reach to the bottom of the hole The ma4or
ad'antage of a liner is the cost of the string is
reduced, as are running and cementing times /uring
the course of the ell, if the liner has to be etended
to the surface (maing it another string of casing), the
string attaching the liner to the surface is non as aAtiebacB string
T=!es of Casing
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THE CASING STRING
