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Knowledge of whatamplitude Is beingmeasured, how ItIs being
measured,and how the tool Iscalibrated Is essentialfor proper
Interpretationof any CBL.
32
Cement Evaluation-Past, Present, and FuturePaul E Pilkington SPE
Conoco Inc
IntroductionCement evaluation began with the calculation oL
cement tops. 1 This calculationassumed gauge holes lind no
channeling ofthe cement through the mud. Calipers werenot available
at that time. In the mid-1930 s,the use (If temperature surveys to
determinethe top of cement (TOC) was documentedin technical
journals. 1-3 Properly run temperature surveys can identify the
TOC, butdistribution of cement-e.g., vertical isolation through
zones of interest-is difficultto ascertain. Radioactive tracer
surveys wererun in the late 1930 s to determine cementtops.
Carnotite was mixed in the lead slurryand cement tops were
determined with agamma ray log. Tracer surveys had the
samelimitations as temperature logs but were nottime-sensitive.
Ref. 1 includes an excellentbibliography.
The acoustic cement bond log (CBL) appeared in the early 1960 s4
and is stillbeing run. The major limitation of the CBLis the
difficulty in identifying small channels. 4-6 More recent
developments in thefield include attenuation-rate6,7 and pulseecho
tools. 68-1O A newer tool that is becoming more available in the
field is the Segmented Bond Tool (SBT).l1 This toolevaluates
circumferential bond over the full360 circumference in 60
segments.Another tool, the Micro CBL , that wouldevaluate
circumferential bond in eight 50segments 12 was under development,
buthas been discontinued because of the success of the SBT. Another
new cement evaluation tool, the Ultrasonic Imager , is inthe
field-testing stage. Examples of theseacoustic circumferential
cement bond toolsare presented later. Future developmentsmay
include more sophisticated tools, suchas the cement volumetric scan
tool. 13 Eachlogging technique currently in use has
limitations.Temperature LogsTemperature logs have been used to
detectthe TOC for many years. 2,3 The most critical factor in the
evaluation technique is theCopyright 1992 Society of Petroleum
Engineers
timing of the survey. Heat from the exothermic reaction as
cement sets dissipates rapidly. Laboratory tests indicate a return
to nearnormal temperatures in 24 hours.6 Earlysurveys also showed
the effects oftime, bottornhole temperature, circulating time,
andthermal conductivity of the surrounding formations on the
temperature profile. 2,3 Thetemperature log remains an economical
andeffective way to determine the TOC and intervals oflarger cement
accumulation. It isnot a direct measure of vertical isolationacross
hydrocarbon-bearing zones; however, if a four-arm caliper is
available, it ispossible to infer good cement displacementif the
TOC agrees closely with the calculatedtop (and full returns were
present duringpumping and displacement of cement).
Fig. IA shows a TOC temperature log.The local temperature
profIle must be knownto avoid mistaking a change in the
thermalconductivity of the formation for a cementtop. Fig. I is a
survey run to determinethe TOC in a deepwater well. The base survey
run at the end of the openhole log runsmade interpretation
possible. Fig. e isfrom a foam cement job. The temperaturepeaks
marked A indicate fracture zbnesfilled with cement. Note the hole
enlargement indicated on the caliper curve in possible fracture
intervals.
Temperature logs, followed by a CBL arerecommended on all foam
cement evaluations. Data in the literature6 indicate thatthe
optimum time to run the temperature logmay precede the optimum time
for the CBLby several hours or more. Compressivestrength
development lags behind the exothermic reaction as cement sets. It
shouldbe possible to record a temperature log andthe CBL on tape
and play the temperatureand amplitude curves back with an
openholecaliper curve on a compressed depth scale.This procedure
facilitates cement evaluationin foam cement jobs and in
conventional cement jobs in fractured formation areas.
The temperature log is still useful in cement evaluation,
particularly in foam cementevaluation and in combination with
othertools. The tool cannot accurately delineatevertical isolation
when run alone. Othertools were developed to fulfill this need.
February 1992 JPT
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,400
~ T O800 ' ;: : >'1200 : -')
1600 ,--,-'(2000 -,2400
2800 i : - - ~
3200 60 70 80OF
Fig. A Temperature survey showingTOC.adioactive Tracers
Radioactive tracers were first used in the late1930's to locate
the TOC for detection witha gamma ray logging tool. 1 A base
gammaray log is normally run with the openholelogs to aid in
evaluation of the postcementing gamma ray log. Carnotite was one
ofthe first materials used as a tracer. It wasblended with the
first 25 (or more) sacks ofcement pumped. Tracers have seldom
beenused in cement since the acceptance ofacoustic CBL's for cement
evaluation.C L ToolThe first tool attempting to quantify vertical
isolation was the acoustic cement bondtool. 6,14-17 The tool
relates bond to thecasing to the attenuation of a casing
arrival,and different companies used various gatingschemes
involving different arrivals. Fig. 2illustrates-some of the
different gate positions that have been used. Most tools measure
peak amplitude and a few measure thearea under the curve. Amplitude
has generally been measured by a fixed gate set toopen and to close
at a fixed time. Gate widthand position are generally set on site
by thelogging engineer. Amplitude can also bemeasured with a
"sliding" gate that openswhen transit time is triggered. This
optionhas a few applications but is not needed onmost logs. One
company has a software program with discriminators that let the
computer select gate position and width. VariousJPT February
1992
0 ~ : : :,-,---------500 .:/-- .1000 /,'--
f1500
J: 2000 - , - Ii2500 20" ,-30003500
BASE lOG \4000 \450060 65 70 75 80 85 90 95 '00 '05OF
Fig. 1B-Deepwater temperature surveyfor TOC."bond index
equations are used to relateamplitude (or area) of a casing arrival
to therelative degree of cement bond to the casing.Logs from
several companies have been runin the same well for Conoco Inc. on
various occasions with sometimes startling results. 17 ,18 Measured
amplitudes on thesecomparisons have ranged from 0 to 35 m Vin
intermediate bond intervals, depending onsuch tool parameters as
transducer diameter,transmitter-to-receiver spacing,
frequency,arrival being measured, and type of measurement (peak or
area). Knowledge of whatamplitude is being measured, how it is
beingmeasured, and how the tool is calibrated isessential for
proper interpretation of anyCBL.Transit time is a measurement of
the timeit takes the acoustic pulse to travel from thetransmitter
through the wellbore fluid, downthe casing, and back through the
wellborefluid to the receiver. When the tool is centered properly,
transit time will be constantexcept for threaded and coupled casing
collars. Fig. 3 is a section from a log run witha properly centered
tool.The CBL is run under pressure to eliminate the microannulus
effect. 19 Fitzgeraldet al 20 note the presence of a microannulusin
more than 90% of the wells reviewed.The thermal microannulus is
normally eliminated by a pressure of 1,000 psi, while produced,
induced, and squeezed microannulimay require higher pressures. 21
Logging in
sPE istinguisheduthor SERIES
133/8 11295/8 29720
CL.CLEAD1
FOAMCEMENT2
3 l l l . . ~ 6 0 : - - - - - = = - - - - - : : 8 : : - O
---"----- 90OF
Fig. 1C Temperature log on foam cement job. (Cl =class.)time
drive while slowly pressuring up withthe tool stopped in a
suspected microannuIus zone can determine the least pressure
required to minimize the produced, induced,and squeezed
microannuli. 21 The lowestpressure required should always be used
inthese cases to eliminate the microannulus effect and to minimize
damage that may becaused by internal casing stress. 4, 17,21,22CBL
Limitations. The CBL must be rununder pressure to eliminate the
microannuIus. The tool also must be properlycentered 17,20 to
obtain a valid log. Thesefactors could be viewed as limitations of
theCBL, but they are simply requirements thatmust be met to obtain
a valid log.Detecting small channels has long beenrecognized as a
real limitation of theCBL. 4,6 A 10 channel results in 90%
attenuation of the free-pipe signal. 4,6 A properly calibrated,
gated, and centered CBLtool still detected all but one 8.3%
channelin a recent CBL tool evaluation. 22Another limitation of the
CBL is the thincement sheath. A cement thickness of < *in. will
not provide complete attenuation ofthe 'casing signal. 23 The thin
cement sheathis occurring more often because improveddrilling-mud
technology often results ingauge holes. An 8 h-in. wellbore with
centered 7-in. casing will have a *-in. cementsheath except where
mud cake is present onpermeable pay zones. If the interpreter
rec-
133
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'EO t f.~
~ ' '1 ::;::E, WID GATE J-.--+1El NARROW GATE H2 NARROW GATE H2
WIDE GATE f--- --- ---..JE3 WIDE GATE f+--- - - -+-j
~ ~ -rl
, . , ~
":,\ o I , . . ~V t
Fig. 2-Amplitude gates used by variouscompanies.ognizes the thin
cement sheath, it is not aproblem.Fig. 4 is an example of a CBL in
7-in.casing in an 8V2-in. wellbore. The openholecaliper from the
density log is shown inTrack I. Note how the amplitude
increaseswhere mud cake is present. The log can beinterpreted
conveniently by relating it to thepercent attenuation for various
cement thicknesses by use of Fitzgerald et al 's2D crossplot
technique.When the mud cake is 1,4 in. thick, cementthickness is
reduced to 112 in. and attenuation rate is only 70% of that with a
perfectbond, as shown in Fig. 20 of Ref. 23. Thelowest stable
amplitude reading is 2 mV, andfree pipe is 62 mV on the log in Fig.
4.These points are connected on a plot of amplitude vs. percent
bond (Fig. 5) to formLine A-B.Mud cake present on the caliper (Fig.
4)from xx250 and xx375 will reduce cementthickness to 112 in.
Perfect bond will now result in an attenuation rate that is 70 % of
thatobtained with a *-in.-thick cement sheath.The chart in Fig. 5
can be entered at 70%bond to obtain the amplitude for perfectbond
with the V2-in. cement sheath (PointC). This value is shifted
horizontally to100% bond (Point D). Line B-D is used tointerpret
bond condition.Good bond is now indicated by either the60% (for
soft rock) value or the 80% (forhard rock) value. Note that
acceptable bondis now indicated by 10 + m V in the soft
rockinterpretation. This value is above the amplitude indicated on
the CBL over this interval in Fig. 4, so no remedial action
isnecessary . The 60% and 80% bond indexvalues have been generally
successful asrules of thumb.The amount of footage of a
particularbond index required for vertical isolation isdefined by
empirically derived charts available in most service company
handbooks .These values generally range from 5 ft of80% bond index
for 5-in.-OD casing to 15ft of 80% bond index for 9S-in.-DD
casing.The values for a 60% bond index are slightlyhigher. Conoco's
experience with these vertical isolation criteria has been good.
Fitzgerald et al. D and McNeely24 reported134
- _. _ - --_ ._ - _.TRANSIT TIME ( _ c ) AMPLITUDE (MV )- --- -
- ._ -_._--> -_ ....._.,._- _._----380.00 280.00GR (GAPI) 0.0
50.000 Z.AXIS v.-:)--- ,--_._
20 0.00 1200.0... I.- ,-\-.. ' - .. ....- .... )-f . , -_ . .-
i:': ~ . : I .. r --. . 1-7
f- :\= .-:I- .. .. f--- I1 :::.::. .. i ,.,:- I' . ' ,--: . ---
F ' ...... -.: L- : .: f::' i II ~ :::: .: .... .. ..... I.: : :.
1'- . . . . I'.. ...1 ::-:.:.:1- :c;:=- , .... ,,, III I..... .:.-
c. .. .. . ...::: ~ : : : t I':: I- i .f- .
.. . , ', I c... . . . . . .
. ..... c -\ ~ : ::. c-- , -I,,' :. I -I-
. ~ t . . ~ ~_. c:' I ,I - l: . I .. l ~ ~ ...I . I -_. 'I H..
'I ~ \:~ ~ . . .i . . ,, -7100 . . irI.. ... I . . . . 1+ ' (_ I ..
. t' -i l: .. I :: I .... ..,
. . . . . . I': ... I :: . c . .......
. . c '-I> 1--- .i - t. . . . i- - . . - . ;I:.:: ' .. . .
... . .. . . . ,- I :: , 1- f- - I: I '.::' . i ' f c -r 11 t ~f
..... . [,i'. ~ ; 2 ; i:: t_ ., . . . . . 172Fig. 3-Properly
centered tool showing stable transit time In partial bond.success
rates of90% on CBL interpretation.Wellbore fluid also will affect
the CBL.Most service company manuals have valuesfor travel time and
amplitude listed for various casing sizes. These values are
generally based on freshwater mud in the casing.Travel time varies
widely for various fluids;Le., a saturated calcium chloride brine
isacoustically faster. 25 This will causefree-pipe transit time to
be less than and amplitude to be greater than the charts
indicate.The opposite is true when oil-based mud isin the casing;
Le., it is acoustically slower and free-pipe transit time will be
greater than and amplitude less than indicated bythe charts. This
is no problem in wells wherefree pipe is present because
interpretationcan be done quickly with a Fitzgerald eta/. D
crossplot. Fig. 6 is a hypothetical example showing the effect of
three wellborefluids with the same pipe-to-cement bond
conditions. One company offered a fluidcompensated CBL26 that
corrected amplitudes for various fluids back to the value forwater
in the casing that seemed to work well.A word of caution: gate
position will differfrom published values when well bore
fluidsdiffer from the fluid used to determine gatingtime. Fig. 7
shows computed free-pipe travel time for one tool with specific
dimensions.It can be seen from Fig. 7 that the gate position will
be different for CBL's run influids other than the fluid used to
derive thepublished char ts . This should not present aproblem when
the log is run because gateposition must always be verified on the
oscilloscope as the log is run.One Other limitation of the CBL is
in dualcasing strings.2728 The gate for the innerstring should be
narrow and set to close onthe backside E > intercept, as shown
inFig. SA. The outer-string signal will not in-
February 1992 JPT
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fT- - - - - - - - - - - . - ~
XX400 1 ---f; ; . . . . . .- -----1t:;
Fig 4 Example of CBl In 7-ln. casing In an 8V2 in. wellbore.
MTEM = measured temperature and CCl=caslng collar locator.)terfere
(in good bond) as long as cementtravel time is 30JLsec Cement
transit timevaries widely. 29 The thickness of the cement sheath
required to prevent interferenceby the outer casing signal will
vary with cement travel time. Interference from the outercasing
string will occur with 5- and 7-in.JPT February 1992
casing (Fig. 8B). This assumes that the inner string is centered
properly. f he innerstring is not properly centered,
interferencefrom the outer string will occur because cement
thickness on the narrow side willchange continuously and may drop
to zero.When it is necessary to evaluate concentric
30
> 20W05 12876
5 0432
A
1 0 20 40 60 80 100BONDFig 5 lnterpretatlon of thin cementsheath
on a CBL.casing strings, both fixed and floating amplitude curves
should be recorded (i f possible) and an x y plot of the wave train
shouldbe recorded. Jutten27 also recommends a20-JLsec-wide gate for
logging in concentriccasing strings. Gate width is not critical
aslong as the gate is set to close 20JLsec afterfree-pipe transit
time.Quality Control for the CBL. The majorproblems with the CBL
have been associated with tool centering, gating, and
themicroannulus effect. A good-quality log isa prerequisite to
proper interpretation. Thelog must be run with sufficient pressure
toeliminate the microannulus with a properlycentered tool. The CBL
must be properlygated and travel time run with a low biaslevel. The
log has to be documented completely, including method of tool
centralizing used, runs with and without pressure,gating, wellbore
fluid, etc. Completedocumentation is needed for all types of cement
evaluation logs (and openhole logs) .Instructions and check lists
used on locationhave proved to be a valuable tool for obtaining
good-quality logs with complete documentation. Any properly trained
CBLinterpreter can do a good job with a correctlyrun and completely
documented log .Attenuation Rate ToolsAttenuation-rate tools5,7
have an advantageover conventional CBL tools in that they arenot
affected by fluid travel time . These toolsmeasure amplitude at two
receivers that are1 ft apart and calculate a compensated
attenuation rate. The only thing that is recorded is the effect on
the acoustic signal as ittravels down the 1 ft of casing.
Attenuation-
135
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The temperature logremains an economicaland effective way
todetermine the TOe andintervals of largercement accumulation.
rate tools have a short-spaced receiver(transmitter-to-receiver
distance :::;1 ft),which permits a computed attenuation rateto be
recorded in casing before interferencefrom fast formation arrivals.
19 Fast formations have an interval transit time less thanthat of
the casing.Attenuation-rate tools are less sensitive totool
eccentricity as long as the sonde is uniformly off center and not
tilted, but still require proper centering of the tool.Fig. 9 is a
section from an attenuationrate log. The interpretation of the
attenuation-rate curve is straightforward. Attenuation rate is a
function of acoustic impedanceand is not related accurately to
compressivestrength. 6 High attenuation rates generallyreflect a
good pipe-to-cement bond.The attenuation-rate logs will be
affectedby small channels and concentric casingstrings. These are
limitations for attenuationrate as well as CBL tools. The
microannuIus effect must be eliminated, tool centering
7SIGN L
>:;20Wc>I
~ 1 2..: S76543
1 0 ~ ~ ~ 2 ~ 0 ~ ~ 4 0 ~ L 6 ~ 0 ~ ~ S ~ 0 ~ ~ 1 0 0SONO
Fig 6 Hypothetical example showingthe effect of three wellbore
fluids underthe same pipeto-cement bond conditions.must be
adequate, and the tool must be gated properly.PulseEcho
ToolsPulse-echo tools were developed with channel detection as a
primary objective. 8 Fig.10 is an example of a channel on a
pulseecho tool. The pulse-echo tools survey approximately 8 in. of
the circumference; eachof the eight transducers covers an area
about1 in. (or less) in diameter. Tests in wellswith simulated
channels22 have shown thatsmall channels will still be difficult to
detect with these tools in larger-diametercasing.Gravel Pack
LogConoco has used the short-spaced densitytool to evaluate a
synthetic cement jobqualitatively. The log was significantly
affected by variations in casing-wall thickness.However, special
processing of the shortspaced density log and casing-inspection
log
/ \\ 9 5/8 SIGN L\
\ \\
//
Fig SA Signal with 7 x 9 -in. casing and cement; transit
time
410390
370
350rE;:: 330
~ 3 1 0290270
S 1 12 14 16eSG 1 0
Fig 7 Arrival time at 3-ft receiver for various fluids.data
enabled a good qualitative evaluationto be made. These data have
not beenreleased for publication.Newer ToolsNew tools on the
horizon include theSBT, I I the Micro CBL, 12 and the Ultrasonic
Imager. 30 These tools survey thecomplete circumference of the
casing andhave the capability to detect smallerchannels.The SBT is
a six-arm pad contact tool withtwo transmitters and two receivers
on eacharm. The transmitters fire sequentially, andattenuation rate
is computed in a mannersimilar to the attenuation-rate tools.
Toolcentering is important with this tool becausemovement off
center will change the lengthof the acoustic signal path between
receiversaround the casing. The tool also has a conventional 5-ft
receiver for wave train presentation to evaluate bond to the
formation. A10 channel between the pipe and cement
5SIGN L
\ 7 SIGN L\\
/\ . /
is 30 p.sec. Fig SB Signal with 5 x 7-ln. casing and cement.136
February 1992 JPT
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20 ~ E N U A T l O ~ ~ ~ " . ~ " ~ ~ 1200AMMA RAY 1000 API330 '
TRANSIT TIME 230.-Ift- 4 CASING COLLAR
MV
tt i
;: I
~ ; t i
1
t
J:fer
ef,.I;
1 i
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A\IRSAV 6
RADMOTV SOOCC DI I\I1P ' lax .Ul 1 R I a v e Th.k- ve cebli
Cament H .pAZEC
-0 . 4 O. 076 O. 076 3. 010. 5 O. 0 ..6 O. 0 3-0 . 6 0.0" '0 O.
060 7. 59.S -1 . 2 O. 052 O. 052 7 . 06. 5 - 1 .6 O. 044 O. 044 ...
. S
- 2 . 0 0 . 036 O. 036 6 . 07 . 5 0 . 026 O. 02&-2 . 4 S. S0
. 020 O. 0206. S 5 . 0-2 . & 0 .012 O. 012
S. S 0 . 004 O. 004 4 . S- 3 . 2 - 0 . 004 -0 . 004 4. 04. S -3
. & - 0 . 012 -0 . 012 3. S- 4 . 0 -0 . 020 - 0. 020 -. S 3. 0-
4 . 4 -0 . on -0 . on
-0 . Ol6 -0 . Ol6 2. S2. S - 4 . &- 0 . 044 -0 . 044 2. 01 .
5 -5 . 2 -0 . 052 -0 . 052 1 . 5
- 5 ... -0 . 060 -0 . 060 1 . 00.7 -0 . 06& -0 . 06&-6 .
0 O. 5O. 5 - 0 . 076 -0 . 076- 99 9 . 0 - . 000 -999 . 000 - 9 .
0
Fig 12-Ultrasonic Imager log section from a U.S. gulf coast
well. AZEC=eccentra lizatlon azimuth.)2. Leonardon, E.G. : The
Economic Utility ofThennometric Measurefllents in Drill Holes
in Connection with Drilling and CementingProblems, Geophysics
(1936) 1, No. I, 115.3. Deussen, A. and Guyod, H. : Use of
Temperature Measurements for Cementation Con-JPT February 1992
trol and Correlations in Drill Holes, AAPGBulletin (June 1937),
21, No.6, 789-805.4. Grosmangin, M. et al : A Sonic Method
forAnalyzing the Quality of Cementation ofBorehole Casings, IPT
Feb. 1961 165-76;Trans., AIME, 222.
5. Albert, L.E. et al. : A Comparison of CBL,RBT, and PET Logs
in a Test Well With Induced Channels, IPT Sept. 1988) 1211-16.6.
JlItten, 1.1. : Parcevaux, P.A. and Guillot,D.J.: Relationship
Between Cement Slurry Composition, Mechanical Properties and139
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uthor
14
Cement-Bond-Log Output, SPEPE (Feb.1989) 75-82; Trans. AIME,
287.7. Gollwitzer, L.H. and Masson, J.P.: The Cement Bond Tool,
Trans. SPWLA (1982)2, Paper Y.8. Froelich, B. et al.: Cement
EvaluationTool-A New Approach to Cement Evaluation, JPT (Aug. 1982)
1835-41.9. Havira, R.M.: Ultrason ic Cement BondEvaluation, Trans.
SPWLA (1982) 1,Paper N.10. Leigh, C.A. et al.: Results of Field
Testing the Cement Evaluation Tool, Trans.SPWLA (1984) 1, Paper
fi.11. Lester, R.A.: The Segmented Bond Tool:A Pad Type Cement Bond
Device, Canadian Well Logging Soc., Calgary (Sept.1989).12.
Schmidt, M.G.: The Micro CBL-A Second Generation Radial Cement
Evaluation Instrument, paper Z presented at the 1989SPWLA Logging
Symposium, Denver, June11-14.13. Brodins, R.A.: Application of the
SonicVolumetric Scan Log to Cement Evaluation,Trans. SPWLA (1984)
2, Paper JJ.14. Grijalva, V.E. : Methods and Apparatus forAcoustic
Logging in Cased Well Bores,U.S. Patent No. 3,729,705.15. Thurber,
C.H. and Latson, B.F.: AcousticLog Checks Casing Cement Jobs, he
Pe-troleum Engineer (Dec. 1960) B84-B88.16. Winn, R.H., Anderson,
T.O., and Carter,L.G.: A Preliminary Study of Factors Influencing
Cement Bond Logs, JPT (April1962) 369-79.17. Bade, J.F.: Cement
Bond Logging Techniques-How They Compare and Some Variables
Affecting Interpretation, JPT (Jan.1963) 17-28.18. Fertl, W.H.,
Pilkington, P.E., and Scott,J.B.: A Look at Cement Bond Logs,
JPT(June 1974) 607-17.19. Pickett, G.R.: Prediction ofInterzone
FluidCommunication Behind Casing by Use of theCement Bond Log,
Trans. SPWLA (1966)1, Paper J.20. Fitzgerald, D.D., McGhee, B.F.
andMcGuire, J.A.: Guidelines for 90% Accuracy in Zone-Isolation
Decisions, JPT (Nov.1985) 2013-22.21. Pilkington, P.E.: Pressure
Needed toReduce Microannulus Effect on CBL, OilGas J. (May 30,
1988) 86, No. 22, 68-74.22. Thornhill, J.T. and Benefield, B.G.:
Injection Well Mechanical Integrity, Report625/9-87/007, U.S.
Environmental ProtectionAgency, Washington, DC (1987).23. Pardue,
G.H. et al.: Cement Bond LogA Study of Cement and Casing Variable
s,
JPT May 1963 545-54; Trans. AIME, 228.24. McNeely, W.E.: A
Statistical Analysis ofthe Cement Bond Log, paper presented atthe
1973 SPWLA Logging Symposium, May6-9.25. Nayfeh, T.H., Wheelis,
W.B. Jr., and Leslie, H.D.: The Fluid-Compensated CementBond Log,
SPEFE (Aug. 1986) 335-41.26. Fons, L.: A Statistical Comparison of
Cementing Techniques by Use of Cement BondLogs , paper SPE 1627
presented at the 1966SPE Amarillo Regional Meeting, Amarillo,Oct.
27-28.27. Jutten, J.J. and Corrigall, E.: Studies WithNarrow Cement
Thicknesses Lead to Improved CBL in Concentric Casings, JPT(Nov.
1989) 1158; Trans. AIME, 287.28. Pilkington, P.E.: CBLs Can
Evaluate Cement Integrity Between Two Casing Strings,Oil Gas J.
(Dec. 10, 1990) 42-46.29. Gearhart, 0.: Compressional Wave Velocity
and Interval Time Tables, FormationEvaluation Data Handbook
Gearhart Industries Inc. (1978).30. Hayman, A.J., Hutin, R., and
Wright, P.V.:High-Resolution Cementation and Corrosion Imaging by
Ultrasound, paper presented at the 1991 SPWLA Annual
Symposium,Midland, June 16.31. Hayman, A.J. and Wright, P.V.:
CementEvaluation by Ultrasonics: Experiments anda New Real Time
Signal-Processing Method, Schlumberger, Clamart, France (1990).32.
Harcourt, G., Walker, T. and Anderson,T.O.: Use of Micro-Seismogram
andAcoustic Cement Bond Log To Evaluate Cementing Techniques, paper
798 presentedat the 1964 SPE Mechanical Aspects of Drilling
Production Symposium, Fort Worth,March 23-24.
SI Metric Conversion Factorsft x 3.048'in. x 2.54'psi x 6.894
757
'Conversion factor is exact.
E-OI = mE+OO = emE+OO = kPa
This paper is SPE 20314. Distinguished AuthorSeries ar-ticles
are general, descriptive presentations that summar-ize the state of
the art in an area of technology by describingrecent developments
for readers who are not specialists inthe topics discussed. Written
by individuals recognized asexperts in the area, these articles
provide key referencesto more definitive work and present specific
details only t oillustrate the technology. Purpo se: To inform the
generalreadership of recent advances in various areas of
petroleumengineering. A softbound anthology, SPE
DistinguishedAuthorSeries: Dec. 19B1-Dec. 19B3 is available from
SPE'sBook Order Dept.PT
February 1992 JPT
