Cementing Basics

7/21/2019 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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Cementing Basics

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