Mud Removal

8/13/2019 Mud Removal

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Mud Removal

Master Table of Contents

1 Objectives2 Introduction

3 The Three Step Process of Mud Removal

3.1 Hole Cleaning

3.2 Conditioning Mud

3.3 Displacing Mud from the nnulus

3.4 !"ercise

4 Criteria for !ffective Mud Removal

4.1 Overvie#

4.2 The Ideal $ellbore Casing

4.2.1 nnular %ap Standards

4.2.2 Sloughing

4.2.3 &lo# from the &ormation Into the $ellbore

4.2.4 &lo#

4.2.5 !ffects of Temperature

4.2.6 Mud &ilterca'e in the $ellbore

4.2.7 Mud Circulation

4.3 The Caliper (og and Mud Circulation

4.4 Mud Circulation !fficienc)

4.5 !"ercise

5 Influence of Casing Standoff

5.1 Overvie#

5.2 *e#tonian &luid+ !ffect of Standoff

5.2.1 (aminar &lo# in an !ccentric nnulus

5.2.2 Turbulent &lo# in an !ccentric nnulus

5.3 Casing Centrali,ation5.3.1 T)pes of Centrali,ers

5.3.1.1 T)pes of Centrali,ers

5.3.1.2 T)pes of Centrali,ers

5.4 !"ercise

6 Casing Movement

6.1 Overvie#

6.2 Reciprocation

6.3 Rotation

6.4 !"ercise

7 Incompatibilit) bet#een &luids

7.1 Overvie#

7.2 $iper Plugs

7.2.1 -ottom Plugs

7.2.2 Top Plugs

7.3 &lo# Regimes

7.3.1 Turbulent &lo# Displacement

7.3.2 !ffective (aminar &lo#

7.3.2.1 Rules for the $!((C(!*. techni/ue in effective laminar flo#+

7.3.2.2 0iscous Spacer for !(&pumping process1

7.4 Chemical $ashes

7.5 Spacers

7.5.1 The Schlumberger &amil) of Spacers

7.5.2 Re/uired Properties of Spacers

7.5.3 M2DP2SH. 3( Concentration Calculation

7.5.4 Composition and &ield Mi"ing Order of Spacers7.6 !"ercise

8 Record 4eeping


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8.1 Record 4eeping

8.2 !"ercise

9 Summar)

10 Test

1

Obe!t"ves

In this training module5 )ou #ill learn to do the follo#ing+

#Identif) the three steps in the mud removal process1

#Demonstrate a 'no#ledge of the processes re/uired in mud removal to accomplishsupport and protection of the casing string1

#Identif) and demonstrate a 'no#ledge of the 6 criteria for effective mud removal1

#Demonstrate 'no#ledge of casing standoff and its importance in mud removal1

#Demonstrate 'no#ledge of the application of casing movement in mud removal1

#Demonstrate 'no#ledge of fluid incompatibilit) considerations and their effects on mud

removal1

#Demonstrate 'no#ledge of appropriate record 'eeping considerations in the achievementof successful mud removal and displacement1

2

$ntrodu!t"on

Mud removal is the most important activit) to accomplish the main goal of primar) cementing 77

complete %onal "solat"onin the #ellbore1 The cement that replaces the drilling mud providessupport and protection to the casing string1 Contamination and channeling of the cement occur

if the drilling mud is not effectivel) removed1 *o slurr) can achieve ,onal isolation under theseconditions1 &or these reasons5 effective mud removal falls mainl) under the cementingoperation1

3

T&e T&ree 'te( )ro!ess of Mud Removal

The three7step process of mud removal includes the follo#ing+

1.Clean the hole 8remove cuttings9

2.Condition the drilling fluid 8to achieve the lo#est possible rheolog)9

3.Displace the drilling fluid 8flush9 from the annulus


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3.1

*ole Clean"n+

Hole cleaning occurs during drilling1 The process includes controlling and optimi,ing mudproperties to manage the hole and 'eep it in gauge 8uniform in si,e and shape91

More than :6; of the hole volume must be in circulation to 'eep a hole clean1

$hen less than :6; of the hole volume is in circulation+

#mud has gelled in #ashed out areas5 or

#there is a build up of cuttings some#here in the hole1

Running a !al"(er lo+is an important step1

The caliper log is a record of the diameter of the #ellbore that indicates

#undue enlargement due to cave7in5 #ashout5 or other causes5 and

#corrosion5 scaling5 or pitting inside tubular goods1

caliper log of the hole is run to

#determine hole volume to compare #ith the volume of fluid in circulation5

#identif) possible problem #ashed7out ,ones from the collected data5 and

#calculate the correct hole volume for slurr) re/uirements from the caliper measurements1

,"(er tr"(is the process of running the drillstring in and out of the hole or to the previous

casing shoe #ithout changing the drill bit1

$iper trips are performed at regular intervals to ensure that+

#the hole is being completel) emptied of the drilled cuttings5 and

#the formations are being controlled1

3.2

Cond"t"on"n+ Mud

The second step in effective mud removal is conditioning the drilling fluid on the last #iper trip

just before runn"n+ t&e !as"n+1 In some cases5 conditioning is done #hen the casing is on thebottom1

Drilling fluid is conditioned to+

#reduce gel strength5

# reduce or optimi,e the-"eld (o"nt8the resistance to initial fluid flo#9 and (last"!v"s!os"t- 8the tangential shearing force in e"cess of the )ield point value re/uired to


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induce a unit rate of shear95

#reduce solids in the fluid 8cuttings9 to less than


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#use of both top and bottom #iper plugs1 More than one bottom plug is recommended1

#use of (reflus&es8chemical #ashes and spacers9 to separate the slurries from the

drilling fluid and to perform efficient hole cleaning1 The cement 8heavier than mud9 has atendenc) to channel in the mud in the casing1 The same applies to the mud 7spacer

interface1 Cement contamination #hile traveling do#n a casing can be ver) dramatic andcan completel) ruin the cement job1

#achievement of turbulent flo,for the most effective mud removal1 If turbulent flo#

cannot be achieved5 ffe!t"ve am"nar lo,89 is the second choice1

4.2

T&e $deal ellbore Cas"n+

!ffective mud removal is greatl) influenced b) the geometr) of the #ellbore in #hich the casing

is run1

!ffective mud removal is influenced b)+

#angular gap standards

#sloughing

#flo# from the formation into the #ellbore

#flo#

#effects of temperature

#mud filterca'e in the #ellbore

#mud circulation

#caliper log and mud circulation

# mud circulation efficienc)

4.2.1

nnular a( 'tandards


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The industr) standard for the total gap bet#een the casing and the #ellbore is ?16 in1 The

minimum standard annular gap is @1=6 in1 n annular gap of less than @1=6 in1 results in acement sheath that is too thin and5 therefore5 ver) fragile and that could be shattered b)drilling7induced vibrations or the impact of perforating1

&or e"ample5 the total gap bet#een a : 6AB in1 casing and its standard hole si,e of ?16 in1 is

?1? in1 8?16 in1 7 :1


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4.2.4

lo,

The casing is centered in the hole1

The ideal standoff is ?@@;1 Schlumberger re/uires that it is not less than =6;1 n ideal

standoff ensures that fluids flo# e/uall) all around the casing1

&luid velocit) 8ftAsec or ftAmin9 is al#a)s higher on the #ide side of an eccentric annulus than on

the narro# side1 The fluid flo#ing in an eccentric annulus ta'es the path of least resistance andflo#s through the #ide side5 #here friction pressure is reduced1

$ithout careful attention to flo# regime5 a channel of drilling mud can remain in an eccentricannulus after the fluid displacement process is completed1 Such a channel can ma'e the entire

cementing job ineffective1

4.2.5

ffe!ts of Tem(erature

ccurate bottom hole static temperature 8*'T9 and bottom hole circulating temperature

8*CT9 are necessar) to determine accurate placement time of both lead and ta"lslurries1

!rrors in placement time can result in premature setting or over7retardation of the slurr)1

The static temperature at the top of the cement should be higher than the bottom holecirculation temperature 8-HCT9 at total depth to ensure that the cement sets up as /uic'l) at

the top as at the bottom1 The result is a more effective cement job1

4.2.6

Mud "lter!ae "n t&e ellbore
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The mud f"lter !aein the #ellbore should be thin and impermeable1 It should not be gelled orunconsolidated1

thin filter ca'e is not moved b) the fluids passing b) it5 nor does it contaminate the slurr) orgreatl) affect the results of the cement job1 %elled or unconsolidated filter ca'e5 ho#ever5 can

contaminate the slurr) and result in a poor cement job1

4.2.7

Mud C"r!ulat"on

Ta'e care to ensure that there is no lost circulation into the #ellbore1 (ost circulation can result

in the slurr) entering the formation instead of filling the annular gap1

The ideal #ellbore has an in gauge diameter hole1 The closer the hole is to in gauge5 the easierturbulent flo# is to achieve1 The more uniform the hole5 the less volume of fluid is re/uired tocomplete each phase of mud removal1

The mud is conditioned to ensure that all mud is movable and5 therefore5 can be removed1

4.3

T&e Cal"(er o+ and Mud C"r!ulat"on

The entire volume of the hole must be in circulation to effectivel) displace the mud from thecasing and the #ellbore1

2se flu"d !al"(ers#ith the caliper log to determine ho# much of the mud in the hole is incirculation1 If parts of the hole are not in circulation5 then mud is not removed and the cement

slurr) b)7passes those sections of the #ellbore1

The caliper log procedure is simple and is performed as often as possible1

The most important step is to run a T lo+8bore&ole +eometr- tool or mult"arm!al"(er9 to determine the difference bet#een the actual open hole volume and the total hole

volume1

lthough t,oarmed !al"(ersare often used5 fourarmed !al"(ersgive a more accuratereading of the hole and should be used #henever possible1

4.4

Mud C"r!ulat"on ff"!"en!-

fter the caliper log is run and the casing is on bottom5 the #ell is circulated at the e"pectedma"imum cementing rate1 t this time5 mud circulation efficienc) is determined1
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The steps in determination of mud circulation efficienc) are

#Drop marersor tra!ersat staged intervals during circulation1 The mar'ers can becolored fluids or objects 8li'e rice9 that can be easil) seen #hen the) return to the

surface1

# Monitor the returning fluids for mar'ers as the #ell is circulated1

#Determine the volume of fluid circulated to return each mar'er from the pump rate andtime1 This volume should be reasonabl) close to the total hole volume determined b) thecaliper log1

#Increase the pump rate and repeat the calculations if the circulated volume and caliperlog volume are ver) different1 s the pump rate increases5 the volume of fluid should

increase1

5

$nfluen!e of Cas"n+ 'tandoff

This section #ill address

#*e#tonian fluid+ effect of standoff

#casing centrali,ation1

5.1

Overv"e,

Casing standoff is an important consideration in mud removal1 In an eccentric annulus5 velocit)differences in fluid flo# bet#een the #ide side and the narro# side occur1 &lo# velocit) ishighest in the #ide side of the annulus #here friction pressure is lo#est and is lo#est in thenarro# part of the annulus #here friction pressure is higher1

5.2

:e,ton"an lu"d; ffe!t of 'tandoff
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$hen t#o pipes of different diameters are hoo'ed in parallel on a flo# line and fluid is pumped

into each from the same source5 the (ressureat both the entrance and e"it of each pipe is thesame1 The velo!"t-of the fluid in the smaller pipe is lo#er than that in the larger pipe at acertain pump rate because friction pressure in the smaller pipe is greater than the friction

pressure of the larger pipe1

Re)nolds number is the ratio of a fluidFs inertial forces to its viscous forces1 The Re)noldsnumber has no dimension5 if consistent units are used in its calculation1

Re)nolds number is defined b) the formula+

$here+

#D E Dimensions of the flo# channel

#0 E verage flo# velocit)

#

E &luid densit)

#

E &luid viscosit)

In the ne"t series of visuals5 observe the steps in the calculation of Re)nolds number1

&or e"ample5 #e can use the Re)nolds number to compare t#o different sets of data1
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The !onstants andv"s!os"t-are the same for both pipes and cancel out5 leaving a relationship

bet#een the diameters and the velocities1 &or t#o pipe si,es 8D? and D95 #here D is t#ice thesi,e of D? 8#hich is a close appro"imation of


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5.2.2

Turbulent lo, "n an !!entr"! nnulus

Turbulent flo,occurs at high flo# rates and results in erratic5 random flo# patterns1 The flo#

rateAflo# pressure relationship is governed b) the inertial forces of the fluid 8ref1 Rheolog)Module91

&or the same fluid in turbulent flo# through the t#o pipes5 the velocit) in the larger pipe is ?1


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s previousl) discussed5 standoffis the ratio of the smallest annular gap to the averageannular gap bet#een t#o pipes #ith different diameters5 if one is completel) centered #ithin the

other1

The graph illustrates the ratio of flo# rate necessar) to achieve turbulent flo# in an eccentric

annulus compared to the flo# rate necessar) to achieve turbulent flo# in a concentric annulus1

bove =6;5 there is little difference in the flo# rate ratio1

Do#n to 6;5 the flo# rate ratio changes almost linearl) to about five times faster on the #ideside than on the narro# side1

-elo# 6; standoff5 the flo# rate ratio starts to increase e"ponentiall)1

There are t#o #a)s to increase standoff from casing+

#Drill perfectl) straight holes1

#2se centrali,ers on the casing1

Perfectl) straight holes are rarel) possible or desired5 so centrali,ers on the casing are used

e"tensivel)1

5.3.1

T-(es of Central"%ers

The three most common t)pes of centrali,ers are

1.bo# spring 8spiral or straight9

2.rigid bo# 8or positive9

3.rigid solid 8slip7on9

o, s(r"n+ !entral"%ershave fle"ible bo#s li'e the leaf springs on old truc's1 The) usuall)

have an outside diameter slightl) larger than the diameter of the hole1

5.3.1.1

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R"+"d bo, !entral"%ers8also 'no#n as positive centrali,ers9 have non7fle"ible bo#s and have

an outside diameter slightl) smaller than the smallest diameter in the #ell1

Since these rigid bo#s #ill not collapse5 it is important to chec' diameters in the #ell5 or the

centrali,er can stic' uphole and prevent the casing from reaching the bottom1

These centrali,ers are t)picall) used

# inside previous casings5 or

#in open hole sections that are in gauge 8uniform in si,e and shape91

Rigid bo# centrali,ers are also /uite common in hori,ontal cementing1 The) are used #hen

do#n#ard #eight on the pipe #ould create an eccentric annulus if the bo# spring t)pe #ereused1

5.3.1.2


R"+"d sol"d !entral"%ers


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6

Cas"n+ Movement

This section #ill address

#reciprocation and

#rotation1

6.1

Overv"e,

Movement of the casing5 either reciprocating 8up and do#n9 or rotating5 is an effective aid in

mud removal1 Satisfactor) results are achieved using movement5 but onl) in combination #ithother good removal practices1

6.2

Re!"(ro!at"on

-ecause it is easiest to perform5 reciprocation 8moving the casing up and do#n9 is the most

common t)pe of casing movement1

Reciprocation is measured in c)cles per minute1 c)cle is one up#ard and one do#n#ard stro'eof the pipe or casing1 The length of each stro'e is usuall) bet#een @ feet and G@ feet and theduration of the t)pical c)cle is from one to five minutes1

&or reciprocation to be effective5 scratchers are fitted to the casing so that mud filter ca'e isscraped off and gelled mud moved1

To free articles in the hole before cement is pumped into the annulus5 movement begins #hencirculation starts and continues until the end of displacement1

There are problems associated #ith reciprocation of a casing+

#The casing ma) become stuc' during movement5 usuall) caused b) the casing ending upin the #rong location do#n hole1

#Other limiting factors are the surge and s#ab pressures generated during casing

movement1

'ur+e (ressureis created during a do#n stro'e1 Surge pressure increases pressure #ithin thehole and can cause formations to fracture1

',ab (ressureis created b) the up#ard stro'e1 S#ab pressure reduces pressure in the#ellbore and can cause a drop in pressure resulting in a 'ic' or blo#out1 In addition5 the #eight

of the casing during movement can result in e"cessive pull on or buc'ling of the casing5 eitherof #hich could lead to casing failure1

6.3

Rotat"on
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Rotation is another casing movement1 In rotation the casing is turned5 #hich causes the gel of

the mud to brea' and increases mud mobilit) around the casing1 s in reciprocation5 rotationstarts at the beginning of circulation and continues until displacement is complete1 This ensures

that an) filter ca'e5 gelled mud5 or other debris is removed before cement is placed in thecasing or annulus1

Rotation is measured in revolutions per minute 8rpm91 T)picall)5 the casing is rotated bet#een?@ and G@ rpm1 Close monitoring of tor/ue is ver) important5 since the rotational motion can

cause the casing to t#ist off and to be lost do#n hole1

Scratchers improve the efficienc) of rotation but are less necessar) in rotation than in

reciprocation1 Some centrali,ers are fitted to aid the s#irling movement of the mud5 ma'ingscratchers even less necessar)1

Rotation re/uires special surface e/uipment5 including cement head s#ivels5 po#er s#ivels toturn the casing5 and a drill collar5 among others1

6.4

er!"se

Casing Movement !"ercise

7

$n!om(at"b"l"t- bet,een lu"ds

This section on incompatibilit) bet#een fluids #ill address+

##iper plugs

#flo# regimes

#chemical #ashes

#spacers

7.1

Overv"e,

Mi"ing a displacing fluid #ith a displaced fluid 8e1g15 cement slurr) and a drilling fluid9 can leadto a complete failure in mud removal and ,onal isolation1 This mi"ture potentiall) results in

detrimental reactions of the t#o fluids5 causing a change in their rheolog)1 These rheolog)changes can result in high viscosit) or gel strength1

Slurr) propert) variations include+

#thic'ening time5
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#fluid loss5 and

#Compressive strength1

ll of these potentiall) result in the loss of a h)draulic bond and failure of the cement job1

Contamination of the different fluids is prevented b) using ,"(er (lu+s 8both top and bottom9

to separate them in the casing1

In addition5 !&em"!al ,as&es ands(a!ersare used to separate fluids in the casing and theannulus1

&inall)5 !om(at"b"l"t- testsare run to evaluate the impact of contamination of the cement b)

the mud1

7.2

"(er )lu+s

$iper plugs are used to 'eep the fluids separated #hile the) are inside the casing1

$iper plugs are of t#o t)pes+

#bottom plug

#top plugs

7.2.1

ottom )lu+s

-ottom plugs are used to remove the mud that is ahead of the preflushes and cement1 The)prevent cement and spacers from falling through the lighter fluids ahead of them1 This

occurrence is particularl) serious in large casings1 dditionall)5 bottom plugs #ipe the casing#all clean from mud ca'e5 scale5 rust5 and other debris1

Debris is pushed ahead of the bottom plug and out of the casing1 If a bottom plug is not run5this debris is pushed ahead of the top plug1 s a result5 the debris is pushed into the casing

bet#een the float collar and the float shoe 8i1e15 the shoe trac'9 and possibl) out into theformation1

s the bottom plug moves into these areas5 it displaces the cement ahead of it and ma'es agood cement job ver) difficult5 if not impossible1
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7.2.2

To( )lu+s

Top plugs are used to separate the cement from the displacing fluid5 #hich is usuall) drilling

fluid1 Top plugs also provide a positive indication of the end of displacement1 $hen the top plugstops do#n hole5 an increase in pressure is recorded on the surface and displacement iscomplete1 This pressure increase is called bumping the plug1

7.3

lo, Re+"mes

Turbulent flo# is the best flo# regime to remove drilling fluid5 based on both e"periments andstatistics1

$hen formation features and other considerations ma'e it impossible to reach turbulent flo#5

effective laminar flo# is used1

7.3.1

Turbulent lo, /"s(la!ement

&or a fluid to be in turbulent flo#5 it must be pumped above a minimum flo# rate5 i1e15 the

!r"t"!al flo, rate.

The fluid particles move in a s#irling5 randomi,ed motion5 #hich aids in the removal of a

cuttings bed in highl) deviated holes1

The critical flo# rate of a given fluid depends on four factors+

1.The rheolog) of the fluid 8i1e15 the thinner the fluid5 the easier it goes into turbulent

flo#95

2.The centrali,ation of the casing or casing standoff 8i1e15 the better centrali,ed thecasing5 the easier the fluid goes into turbulence all around the casing95

3.The annular gap or clearance bet#een the casing and the hole si,e 8i1e15 the smaller the

gap5 the easier the fluid #ill go into turbulence95 and

4.The fracture gradient of the formation1

The fracture gradient of the formation is an indirect factor5 but it must be ta'en into account1 Ifthe pressure re/uired to achieve turbulent flo# is higher than the fracture gradient of the

formation5 the formation ma) rupture5 and losses of fluid #ill result1
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20/26

Conditions for achieving the differential velocit) criteria include+

#Minimi,ing the velocit) difference bet#een the displaced and displacing fluids to establisha flat interface1 The sum of the gravitational force and the friction force of the displacing

fluid in the #ide side of the annulus must be greater than that of the fluid being displacedin the narro# side of the annulus1

#Maintaining the annular flo# rate belo# a certain value1 $hen the displacement rate is

too high5 the displacing fluid tends to b)pass the fluid to be displaced rather thandisplacing it uniforml) around the annulus1

This standard establishes a ma"imum flo# rate for the placement of a slurr)1 It ensures that nodisplacing fluid b)passes a displaced fluid through the #ide side of an annulus1

7.3.2.2

@"s!ous '(a!er for (um("n+ (ro!ess.

viscous spacer5 the M2DP2SH. 3(A3(O5 has been developed to meet the criteria of the !(&

regime1 This spacer has an adjustable viscosit) based on changing the concentration of D?G: inthe spacer1 $hen pumping 3(A3(O.5 a minimum of 6@@ feet in the annulus or @ to G@ bbl of chemical #ash should be used ahead of the spacer to start to disperse thedrilling fluid1

The drilling fluid must be conditioned to reduce gel strength and rheolog) and remove solids1The viscosit) of cement slurries ma) need to be adjusted for the slurr) to follo# the pressure

gradient hierarch)1 D?6 is used for this purpose1

7.4

C&em"!al as&es

Chemical #ashes are #ater7based fluids #ith lo# viscosities and densities 8much li'e #ater9 and

are ver) eas) to get into turbulent flo#1 The) are the preferred fluid for turbulent flo# #ashes1

The chemical #ash is pre7mi"ed in a tan' but can also be mi"ed on short notice b) adding the

products to the displacement tan's in the field as the #ater is being added1 There is too muchproduct for C$B or C$?@? to be added to the displacement tan's as the #ater is being added5

and this procedure is not recommended for these t#o products1

Mi"ing regimen for chemical #ashes

)rodu!t C7 C100 C8 C101 C8' C101'

$ater G?16 G?16 G?16 G? G?167G? G?7:1=6

D? @16 @16 @16 @16 @16 @16

=r @16 @16 @16

&G@ @16 @16

D


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3.add = if re/uired and agitate the mi"ture #ell5 and

4.add &G@ or D


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dding surfa!tantsto these spacers ma'es them compatible #ith oil7based muds1 $hensurfactants are used5 the spacers are designated M2DP2SH. 3TO5 3SO5 and 3(O spacers1

Schlumberger uses t#o spacers for high7temperature environments1

'(a!er lo, T-(e nv"ronment

M2DP2SH $HT. Turbulent High7temperature5 fresh or salt #ater

M2DP2SH 3!O. !ffective (aminar High7temperature5 oil7based

7.5.2

Re?u"red )ro(ert"es of '(a!ers

The re/uired properties of spacers are+

#compatibilit) #ith the drilling fluid and the cement slurries in the #ell5

# stabilit) and suspending properties even at high temperatures5 to avoid allo#ing the#eighting agent to drop out of suspension5

#controllabilit)5 so the densit) and rheolog) properties are the same in the lab and in the

field5

#provision of good fluid loss control5 since it #ill be used across permeable pa) ,ones5 and

#environmentall) safe and eas) to handle in the field1

7.5.3

MA/)A'*> B Con!entrat"on Cal!ulat"on

%raphs from the Cementing Materials Manual similar to the one at left are used to calculate the

concentration of D?G: needed to achieve a specific rheolog)1

&or e"ample5 use the ?@@7rpm reading on the &** 6 and read the plot to determine theconcentration of D?G: needed if the &** 6 measures the mud at


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8

Re!ord ee("n+

Comprehensive record 'eeping and informed field personnel are important to successfulcompletion of the pre7cementing process1

The mud removal procedures performed for each job are recorded to confirm proper mud

removal prior to cementing and to communicate #ith appropriate personnel1

The follo#ing records are 'ept+

#mud conditioning5 including the rate and time5

#the number5 location and t)pe of centrali,ers run on the casing5

#motion of the casing during the procedure5 including t)pe 8reciprocating or rotating9 and

duration5

#times plugs are dropped5

#densit) and rheolog) of the spacers5 and

#the correct volume of preflushes pumped1

8.1

Re!ord ee("n+

s much data as possible must be recorded on the PRISM. laptop1

The minimum data re/uired includes+

#thedensities of the pre7flushes5 slurries5 and5 if possible5 the displacing fluid5

#all the flo# rates+ 8the displacement pump rate is the most important and usuall) thehardest to record since the displacement is often done #ith the rig pumps1 *evertheless5ever) effort should be made to get and record this data95

#the surface pressure throughout the job1 The surface pressure during displacement can

give valuable information if losses occurred do#nhole5 and

#

all notable events during the job5 recorded on the PRISM5 such as changes in pump rateor densit)5 shutdo#ns5 and pea's in pressure5 etc1

This information ma) be helpful in e"plaining post7job occurrences1

ll up7to7date #ell data should be included on the service report5 including the actual casingdepth5 etc1

The service technician or field engineer on the rig is in direct contact #ith the client1 He or sheneeds access to an) information that could ma'e a vital difference in the evaluation or design of

a job1 Record all significant information and contact the appropriate service technician or fieldengineer #hen post7job anal)sis is re/uired1

8.2

er!"se


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Record 4eeping !"ercise

9

'ummar-

To ensure that drilling fluid has been ade/uatel) conditioned prior to cementing5 the ma"imum

pumping rate for the job 8usuall) the displacement rate9 is chosen and at least one hole volumeis circulated before the cement job is begun1

The casing is centrali,ed to ensure an optimum standoff1 In no case should the standoff be lessthan =6;1

$henever possible5 reciprocation or rotation of the casing is performed during mud removal1Scratchers are used to improve the efficienc) of casing movement in mud removal1

-ottom plugs are used5 if possible5 bet#een each fluid interface to reduce contamination offluids inside the casing1

Slurr) placement is optimi,ed b) using a turbulent flo# regime5 if possible5 or an effectivelaminar flo# regime if turbulent flo# is not possible1

Chemical #ashes are used #henever possible1 These fluids are easier to get into turbulent flo#than spacers1 Chemical #ashes are more cost effective and are eas) to prepare and handle1

$hen M2DP2SH. spacers are used5 their properties are controlled5 especiall) densit) andrheolog)1 The cement slurr) properties must also be controlled1 $henever possible5 slurries and

spacers are batch7mi"ed to ensure homogenous properties for each fluid1

ll fluids should be lab tested and field chec'ed for compatibilit) to avoid adversemudAspacerAcement reactions1 /uic' field test can be performed b) slo#l) pouring one fluidinto the other1 If5 after slo#l) stirring the mi"5 the fluid thic'ens and cannot be stirred5 the DT!

or lab should be consulted1

&inall)5 all #ell data must be correct on arrival on location1 If conditions in the #ell have

changed5 the design ma) have to be rerun at the district1 In an) case5 if the #ell has changed5the field service manager or DT! should be contacted regardless of the time1


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Mud Removal

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