cementing basics
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Cementing Basics
Primary Cementing
Repair (Squeeze Cementing)
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Why Cement?
Completes the isolation step that was startedwith casing
!Pressure isolation!Pipe support and protection
"#terior corrosion
Pressure control
$oad and %orce application support
!$ea&o%% control ! pre'ents cross%low?
!Water in%lu# control
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Statistics
Primary cementing cost aout * o% wellcost
+out ,* o% primary cement -os requiresqueezing
.otal cost o% cementing when squeezing is
required is aout ,/* o% well cost .ypical numer o% squeezes required to %i#
a prolem in a primary cement -o 0 1
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Cement Circulation
Path2 3own the casing and up the annulus
Concerns2
! Cement density 's pressure 4window5 %rom %ormation
! Cement ond etween pipe and %ormation
! Cement pump time
! +ility to place the cement o'er the whole column
(%luid loss control6 correct 'olumes6 pumpaility)
! Cement strength de'elopment
! .he quality and longe'ity o% the seal
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Cementing the annulus
o% the casing and open
hole %orms a seal that
e%%ecti'ely isolates
pressure and supports
the casing
Cementing the well ! pro'ides
pipe protection and support and
gi'e sur%ace pressure control
:ot all strings need to e
cemented ac& to the sur%ace
! it may e ad'antageous notto cement ac& to sur%ace
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.he most important sectiono% the cemented column is
near the casing shoe ! .he
strength at this point must
e su%%icient to withstand
the highest weight mud that
will e used in the ne#t
section to e drilled
+%ter cementing6 the
well is drilled ahead %or
a %ew %eet and a 4shoe;test5 is done to simulate
the highest mud weight
e#pected
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:eat (no additi'es) cement is a manu%actured product with a speci%ic
grain size and properties .he slurry properties %or the well are made to
order y incorporating a range o% additi'es into the mi#ed slurry that
a%%ect pump time at temperature6 %luid loss control6 staility to thermal
conditions6 and gas migration
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.he %inal slurry design has a certain slurry density6 usually etween ,,
and ,9 l>gal6 with typical class or @ eing aout ,7A l>gal ore
water can e added6 ut the water will separate as it sets6 resulting in
channels or wea& cement
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8luid 3ensity Balance ! used to get %luid density in l>gal
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eneral properties o% cement slurries e%ore additi'es :ote that without
additi'es6 the class and @ slurries would not e usale %or many wells
Correct slurry design is critical %or cement success
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"'ery cement design
must ta&e into account
the temperature and
pressure e#tremes in the
well $ow temp retardsthe cement set time
@igh temp accelerates the
cement set time
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Temperature vs TVDss
-11500
-10500
-9500
-8500
-7500
-6500
-5500
-4500
-3500
-2500
-1500
-500
0 20 40 60 80 100 120 140 160 180 200 220 240 260
Temperature (degF)
TVDss
Seal-A-01 MTEMP3
Seal-A-01 MTEMP4
Seal-A-01 MTEMP5
NS29 MTEMP
NS27
Top of Slush Zone
Base of Slush Zone
Top of Pe!afos"
Base of Pe!afos"
"%%ect o% Perma%rost on
temperature pro%iles !
+las&a Well
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Temperature-50#
$10#
%eo"he!al
2&1#'100(
Depth
$200#
8900(T)*
1850(
100(
$30#
eothermal gradient
%rom an +las&a well
through the
perma%rost
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odi%ying the Set .ime o% the
Slurry +ccelerators speed it up
!calcium chloride
!sodium chloride!gypsum
Retarders slow it down
!lignins6 sugars6 cellulose!some drilling muds
!sodium chloride
.he sodium chloride
may e an accelerator or
a retarder6 depending onamount o% salt and other
%actors
.he e%%ect o% mud on theset time o% cement is
unpredictale
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Cement without a retarder in a hot %ormation will set up too rapidly
o%ten e%ore the cement has een completely displaced into the annulus
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Cementing Prolems .hat ust
e +ddressed in the 3esign, Well Control ! rememer6 until the cement sets6 it
must control the pore pressure li&e any other wellcontrol %luid
D Pumpaility ! .he pump time must e long enoughto completely displace the cement %rom the pipe tothe annulus
1 8luid $oss Control !
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Well Control
Wor&ing in the slurry density 4window5
!Pore pressure estalishes the lower limit o%
slurry density!8racturing gradient estalishes the upper limit
o% slurry density
Cement density normally is ,7A l>gal!.ypical light weight cement is ,, to ,D l>gal
!@ea'ier weight cements may e up to D1 l>gal
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$ight Weight Cement
ethods!+dd more water ! poor method6 o%ten creates
%ree water channels and poc&ets!8iner grind cement ! allows more water
addition and &eeps the water in the cement
!$ight weight %illers
Small (,E to /E micron)6 air %illed 4alloons5 suchas ceramic or glass
$ight weight %illers
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@ea'y Weight Cement
3ensities to D1F l>gal
! Sand
! @ematite!
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Cement Prolems and 8ailures
Prolems?
! Cement at shoe not strong enough to contain pressure
o% deeper zones! must repair e%ore drilling ahead! Casing not centralized ! lea'es mud channel on low
size ay lea& now or later Requires squeeze
! Casing not mo'ed during cementing ! you need to get
mud displacement y cement to get a good -o!:ot enough cement in annulus to %unction as a arrier
@ % i h h l ?
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@ow %ar is cement rought up the annulus?
inimumDEE to EE
%t ao'e
the shoe
%t6 cement
density is E9
psi>%t
D .ime
1 Cost
A :ot
understanding
protection need
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Well 8ailure Statistics
WellsDeveloping
Leaks
Well Life Prior to Casing Leak, Years
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Common contaminants and ops
that degrade cement ond ? Slurry contamination ! primarily mud during
displacement
Sul%ate e%%ects on mi#ing slurry and on set cement ! use
sul%ate resistant cement
+cids ! @Cl ! no e%%ect @8 ! signi%icant local e%%ect ! ut
shallow without channels
"#plosi'es (per%orating) ! usually minor e%%ect i% there are
no channels
.ypically6 i% a cement -o 4rea&s down5 a%ter per%orating6 acidizing6
sol'ent6 or %rac6 the prolem is that an e#isting mud channel in the
cement has een distured
$ & %% % t % th l t d h d t d th t ill t
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$ea&o%% o% water %rom the slurry creates a dehydrated mass that will act
li&e set cement .he result is the same the cement slurry cannot e
pumped through the annulus
3 h d ti % th l
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3ehydration o% the slurry
causes a plug in the
annulus
Since the %irst o-ecti'e o%a cement displacement is to
remo'e the mud %ilterca&e6
the increased %luid loss has
to e controlled y the
cement slurry
$ t th % ti
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$ow strength %ormations
(low %racture gradient) pose
a special prolem
Created or natural %racturescan e a thie% zone %or
whole cement ! causing
less height in the annulus
:atural %ractures can alsoact as a %luid loss site %or
lea&o%% %or water %rom the
cement ! the result is
dehydration o% the cement
slurry
Fluid loss through wide natural fractures is often very hard to
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Fluid loss through wide natural fractures is often very hard to
control requiring particulate and/or flake fluid loss control
additives.
Salt zones can create
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Salt zones can create
ca'ities or washouts
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Cement 3isplacement
.he %irst part o% the cement slurry remo'es themud ca&e ! and contaminates the cementContaminated cement will not set up
Where does the mud contamination come %rom?! ud system in the annulus
!
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Cement 3isplacement in the Pipe
.he .wo;Plug displacement system
!Patented and used since aout ,I,
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.he .wo Plug System @elps isolate the
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.he .wo Plug System ! @elps isolate the
cement %rom the mud and the
displacement %luid
.he top plug is solid and the ottom plug
is hollow and has a diaphragm that
ruptures when the ottom plug hits the
%loat collar
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"'ery time a plug sweeps through the casing6 a small amount o% mud and
other deris is pushed ahead o% the plug .he contaminated cement in
this area will not set or will set 'ery slowly
8or this reason6 a %loat collar6 set a -oint ao'e the shoe will &eep thecontaminated cement at the end o% the displacement inside the casing !
not at the shoe
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Cementing "quipment in the
Casing String 8loats ; collars and shoes
!wear points ; watch %or erosion ; particularly
with arasi'e muds such as iron caronates
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+ single wiper plug dropping tool6 showing 4ail5 release mechanism
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8loat collars are one to three -oints
ao'e ottom depending on the
length o% the string and the diameter
o% the casing
"#amples o% equipment used on the B@+ (ottom hole assemly) during
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"#amples o% equipment used on the B@+ (ottom hole assemly) during
casing running .he %loat equipment helps pre'ent ac&%low o% cement
a%ter %ull displacement .he guide shoe helps guide the casing past
ledges and doglegs (sudden hole direction changes) during pipe running
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+ %loat collar .he
'al'e pre'ents
ac&%low o% %luids a%ter
the cement has een
displaced "lement
wear during pumping
o% large 'olumes o%
cement may cause%ailures necessitating
holding pressure on the
well a%ter cement
displacement
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Hther "quipment
Centralizers
Scratchers
Both help to impro'e the cement ond and
seal etween casing and %ormation
Gse o% centralizers impro'e the aility o% the cement to surround the
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Gse o% centralizers impro'e the aility o% the cement to surround the
pipe6 displacing the mud and creating a channel;%ree seal Centralizers
also assist running casing in de'iated sections
+rea o% undisplaced mud ! a mud channel
remains6 requiring squeezing
8low pro%ile in a well with decentralized pipe :ote .hat most
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8low pro%ile in a well with decentralized pipe :ote .hat most
o% the %low comes along the top o% the pipe .his a%%ects
cleanup and residence time o% the %luid on the wellore .he
lower section o% the wellore may remain uried in cuttingsand ne'er ha'e contact with any o% the circulated %luids
a-or %low area
B i li
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Bow spring centralizer
.his is a de%ormale6 ut
normally wea& centralizer
that may lose per%ormanceand centralization with
increasing string weight
and increasing wellore
de'iation
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Straight 'ane casing
centralizer .his is a slip;
o'er type that %loats
etween the couplingsunless loc& rings are
added
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Spiral centralizer6 assists in decreasing drag and helps centralize casing
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Roller centralizer %or reducing string drag during running long casing
strings in de'iated holes .hese are most e%%ecti'e as casing is run
through larger casing
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