3_principle of measurement2

Internal Use Only

Cement Bond Evaluation

Physics Of Measurement&

Log Quality Control

Internal Use Only

Physics of Measurement

Internal Use Only

Knowledge Review

Internal Use Only

CBL-MSG Measurement Principle

Acoustic Signal

Times

Amplitude

T0

- T0 : Firing Pulse

|--- Resulting Sound--|

- Resulting Sound wave : as recorded at the Receivers

Internal Use Only

Basic CBL Principle Similar to a Ringing

BellWhen Fluid is behind Casing, pipe is free to vibrate [ loud sound ]When the casing is bonded to hard cement,casing vibrations are attenuated proportionally to bonded surface

GoodGoodBondBond

NoNoCementCement

Internal Use Only

CBL Measurement PrincipleBasic Tool Configuration• 1 Transmitter – 2 Receivers

– 3 ft Receiver for Pipe Bond Measurement

– 5 ft Receiver for MSG Analysis

• TOOL MUST BE CENTRALIZED!

3 ft

5 ft

Tx

R3

R5

Internal Use Only


Pipe Bond

Internal Use Only

Pipe Signal• Defined as: The amplitude of the first arrival (E1) in mV.• Is a function of cement bond to casing• Measured at the three foot receiver

– Amplitude inversely proportional to degree of cement bond to casing

• Provides means of calculating travel time• Selection of E1 is dependent upon user input and must

be established in software in order to be properly analyzed!

Internal Use Only

Measurement Gates• To identify and analyze E1 and properly calculate

travel time the user must define two measurement gates in the acquisition software.– Amplitude Gate– Travel Time Gate

Internal Use Only

Free Pipe Amplitude

T

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2

•When the casing is free of cement then it is free to vibrate.•This is known as Free Pipe. The amplitude of the first arrival is known as Free Pipe Amplitude.•Measurement gates are set according to free pipe values.

Travel Time

Amplitude

Internal Use Only

Waveform Time AnalysisCASING ARRIVALS TRAVEL TIME

T Casing = 57 sec/ftT Cement = 75 sec/ftT Formation ≈ 100 sec/ftT Fluid ≈ 189 sec/ft

TTC = FLUID + CASING + FLUID

3 in x 189 s/ft 3in x 189 s/ft

= + 3 ft x 57 s/ft + 12 in/ft

12 in/ft

= 265.5 s

Internal Use Only

Amplitude Gate• The amplitude gate is setting according to free pipe

travel time values determined by casing size.• TT – 10uS• Gate Width should be 32 – 40 uS wide.• Allows us to pinpoint and focus on the E1 Peak.

Internal Use Only

PIPE AMPLITUDE VS TRAVEL TIME Casing size Casing wt Pipe amp Travel time 4 1/2” 9.5 81 m.v 254 usec 11.6 81 m.v 254 usec 5 ” 15 76 m.v 258 usec 18 76 m.v 258 usec 5 ½” 17 72 m.v 269 usec 20 72 m.v 269 usec 7” 23 62 m.v 289 usec 26 62 m.v 289 usec 9 5/8” 53.5 51 m.v 332 usec

• NOTE: WhileFree pipe amplitude is a fixed value based on casing size, but, travel time is tool dependent.

Internal Use Only

The travel time and amplitude gates are independent of each other

Travel Time

E1

Internal Use Only

Travel Time Gate • The travel time gate functions in the same manner as the

amplitude gate but adds an additional threshold control.– Travel Time Gate set at TT-10us– Gate Width 32 – 40 uS– Threshold Level 90% Bond or better.

• Client may specify.

• Travel time is then calculated by the software by recording the time elapsed from firing to the time that the first peak crosses the threshold within the specified interval.

• Essential for determining proper Travel Time• Travel time is a LQA Curve

– Can identify eccentralization– Indicator of good cement bond to casing

Internal Use Only

Incorrect travel time due to road noise

E1NOISE

CORRECT TT

TT LOG

Internal Use Only

Pipe Amplitude Measurement PrinciplePipe Amplitude Definition• Amplitude of First Arrival in mV• Measured at 3 ft Receiver• It is a function of the Casing-

Cement Bond3 ft

Tx

R3

R5 Travel Time Definition• Time elapsed from T0 to First

detected Arrival (above threshold level)

• T T is used as Log Quality Control Indicator

Internal Use Only


Micro Seismogram (MSG)

Internal Use Only

Waveform Time AnalysisFORMATION ARRIVALS TRAVEL TIME

2” T Casing = 57 sec/ftT Cement = 75 sec/ftT Formation ≈ 100 sec/ftT Fluid ≈ 189 sec/ft

TTF = FLUID + CEMENT + FORMATION + CEMENT + FLUID

3 in x 189 s/ft + 2 in x 75 s/ft = 2 x + 3 ft x

100 s/ft 12 in/ft= 419.5 s

Internal Use Only

The MSG SignalMSG: MicroSeismoGram• 5 ft Receiver for MSG Analysis• Allows easy differentiation

between casing and formation arrivals

5 ft

Tx

R3

R5

Internal Use Only

MSG Algorythm Principle• Recorded Waveform at one

depth (Total Energy)

• Waveform is cut for only Positive Peaks (Clipped X-Y)

• Rotated 90 Degrees• Peaks are compared to a Grey Scale• Peaks are shaded and presented from Top View• Final Picture Vs Depth is obtained

Internal Use Only

Essential Calculations• Operational Considerations

– Travel Time Calculation• [(CSID-ToolOD) X T Fluid uS/In)] X 2 + (T Steel X Distance)

– 3’ Amplitude and Threshold Gate Settings• Gate open = TT-10uS• Gate Width = 32-40us• Threshold set at 1mV

– 5’ Gate settings• 3’TT + 114 uS• Threshold set at 1mV

– Radial Mapping Receiver Amplitude and Threshold Gates• 3’TT – 57uS• Threshold set a 1mV

Internal Use Only

Wellbore and Waveform Response

Transmitter

3 ft Receiver

5 ft Receiver

Transmitter

3 ft Receiver

5 ft Receiver

Transmitter

3 ft Receiver

5 ft Receiver

Transmitter

3 ft Receiver

5 ft Receiver

Internal Use Only


Log Outputs &

Examples

Internal Use Only

CBL-MSG Standard Outputs Presentation

•Transit Time TT in micro-seconds [s]•Pipe Amplitude in millivolts [mV ]•MSG Microseismogram [wafeform visual representation]•Gamma Ray [GAPI]•Casing Collar Locator

Internal Use Only

CBL-MSG Standard Outputs

•Transit Time TT in micro-seconds [ms]• Log Quality Control

•Pipe Amplitude in millivolts [mV ]• Quantitative measurement of waveform energy

•MSG Microseismogram [wafeform visual representation]

• Qualitative Analysis of sound• Qualitative indicator of the presence of solid materials between the casing and the formation

•Gamma Ray and CCL as auxiliary curves for Correlation

Internal Use Only

Free Pipe

Internal Use Only

Free Pipe

• LQC– “Chevron Effect” visible in MSG– Free Pipe Amplitude corresponds with known values– Travel Time is correct for tool specifications– Pipe Amplitude decreases in collars– Travel Time increases in collars.– Depth matching between Chevrons, Pipe Amplitude, Collars

and Travel Time

Internal Use Only

Free PipeGAMMA RAY

0 150TRAVEL TIME

200 300

AMPLITUDE0 100

AMPLIFIED AMPLITUDE0 10

CBL WAVEFORM-20 20

CCL

Y50

Y75

ChevronFP Amp

Collar

TT

DEPTH MATCH

Internal Use Only

Good Bond

• LQC– Low Pipe Amplitude– Travel Time

• Stretching• Cycle Skipping

– MSG • Missing Casing Line (Good Bond To Casing)• Presence of Shear and Formation Waves (Good Bond To

Formation)– Gamma Ray follows MSG

• Depth Match

Internal Use Only

Shear Waves

Stonely WavesLow Pipe Amplitude

Cycle Skipping

Gamma Ray Depth Match

Internal Use Only


• Practical Exercises– Take Warrior .db files (Provided By Instructor)

• Set up service in recalculate• Set gates at proper values for casing size and tool• Adjust gates and playback logs to alter outputs

Internal Use Only


Factors Effecting The Log

Internal Use Only

Tool Eccentering

Internal Use Only

Tool Eccentering

Causes for Eccentralization5

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T

• Improper Equipment Selection• Centralizers vs Casing Size

• Missing or Broken Centralizer(s)

• Weak Centralizers in deviated wells

• Tool damaged and or bent• Damaged Casing

Internal Use Only

Eccentering

3 FT

TIME AXIS

TRANSMITTER FIRING

TOOL ECCENTRALIZATION CAUSES SIGNAL AMPITUDE TO REDUCE DUE TO DESTRUCTIVE INTERFERENCE.

Internal Use Only

Eccentering Analysis

There will be destructive interference from different sound paths

Waveform from close tool side to casing

If the tool is eccentered

Threshold T0

TT

Short Path WaveformResulting Waveform

Waveform from far tool side to casing

Delayed Waveform

Result is a Bad Log

not recoverable in Recalculation

Normal Waveform

Resulting waveform has lower amplitudeResembling a zone of Good Cementbut with shorter Transit Time [≈ 4 s

less]

Internal Use Only

CBL Amplitude Vs Tool Eccentering

Internal Use Only

Quality Checks for Travel Time CurveCentralization is critical to proper tool performance.

¼” of eccentralization can cause up to a 50% reduction in signal of E1 due to destructive interference.

Eccentralized logs cannot be fixed by recalculation.

The Travel Time should not vary by more that +/- 4 microseconds from the free pipe travel time. It should be fairly straight with little or no wobble and should Increase in the collars.

The free pipe travel time for the log can be found in the chart book inside the manual for the tool you are using. Travel Time seen in free pipe should reflect the value specified in the manual or calculated.

Internal Use Only

Effects Of Good Cement

Internal Use Only

Stretching

E1 decreases and TT is detected on a non linear portion of E1

Delta T STRETCHING is the TT increase from its value in free pipe

In cases of Good Cement

Threshold

E1T0

TT

Free Pipe Signal

TT’

T

Good Bond Signal

Internal Use Only

TT Cycle Skipping

E1 could not reach Detection Threshold LevelT T skips to the end of the gate window........this is known

as CYCLE SKIPPING

In cases of very Good Cement

Threshold

E1 E3

E2

T0

TT TT

Internal Use Only

Micro Annulus&

Channeling

Internal Use Only

Micro AnnulusDefinition: Is a gap a few thousandths of an inch wide between the

casing and cement often caused by shrinkage of casing after cement sets

Often will provide hydraulic isolation. It will usually not pass any substantial volume of liquid.

Casing can be pressured up while logging to expand the casing and close the gap (typically 1000-2000 psi)

The 5 typical causes of a micro-annulus are:• Thermal Micro Annulus.

• Produced Micro Annulus.• Induced Micro Annulus

• Constraining Forces• Special Coatings on Casing

Internal Use Only

Micro AnnulusE1 amplitude resembles a poorer bond than

actual• Only a pressure pass can be done to

eliminate the micro annulus

Pipe Amplitude: Poor Bond

T

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Internal Use Only

Channeling/Irregular Bond• If problems occur during the cementing

process or borehole conditions disturb the cement during the cementing process then portions of the casing may become less bonded than the rest.

Pipe Amplitude: Poor BondT

5

3

2

Internal Use Only

Channeling

• Causes– Problems encountered during the cementing process;

• Equipment Failure• Cement Contamination• Loss of continuity while pumping

– Infiltration of the cement by formation fluids or gasses.– Washouts– Poor Mudcake Removal– Casing Centralizers

Internal Use Only

Zero Pressure applied at surface

Internal Use Only

With 2000 psi surface pressure applied

Internal Use Only

With PressureWithout Pressure

Internal Use Only

Fast Formation

Internal Use Only

Fast Formation

T

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Fast Formation ArrivalsIn cases of good cement andformation slowness < steel

slownessformation arrival arrives first

The transit time and CBL amplitude

will be affected

T Dolomite= 43.5 sec/ftT Limestone = 47.5 sec/ftT Anhydrite = 50.0 sec/ft

Internal Use Only

Fast Formation

T

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2

•In fast formation the Pipe Amplitude and Travel Time will be the values of the formation and not the casing.•In the presence of FF arrivals, CBL Evaluation is possible, but, difficult. Since the arrivals of E1 is that of the formation and not from the casing special precautions must be taken.•Know the environment you are logging in!•In most cases the CBL tools used in these type environments are modified to delay the waveform by 130uS.

Internal Use Only

CBL Qualitative InterpretationCONDITION TRANSIT

TIMEPIPEAMPLITUDE

MSG

Free Pipe NORMAL HIGH Casing ArrivalsUsually No Formation Arrivals

Good Bond to Casing & Formation

NORMAL to HIGH / NOISY

LOW No Casing ArrivalsFormation Arrivals

Good Bond to CasingNot to Formation

NORMAL to HIGHCAN BE NOISY

LOW No Casing ArrivalsNo Formation Arrivals

Poor Bond to Casing NORMAL MEDIUM to HIGH

Strong Casing ArrivalsNo Formation Arrivals

Microannulus NORMAL MEDIUM to HIGH

Formation ArrivalsCasing Arrivals

Channeling NORMAL MEDIUM to HIGH

Formation ArrivalsCasing Arrivals

Fast Formations LOW HIGH Formation ArrivalsNo Casing Arrivals

Eccentered Tool LOW LOW DEPENDS

Internal Use Only

Cement Bond Evaluations

Quantitative Analysis

Internal Use Only

CBL Quantitative Interpretation• ATTENUATION (Mathematical)

– Logarithm of E1 amplitude– Can be used to calculate values such as cement

compressive strength.– BOND INDEX

Attenuation in zone of interest [dB/ft]

BI =

Attenuation in best Cemented Section [dB/ft]

Internal Use Only

Bond Index

Internal Use Only

Zone Isolation Based on Bond Index

55 66 77 88 99 1010

3030

2525

2020

1515

1010

55

Bond Index = 70 %Bond Index = 70 %



Casing O.D. [in]

Interval

[ft]

Internal Use Only

CBL Quantitative Interpretation

M1 ChartCasing Data

O.D. 7”, 29 lbm/ft

Cement Compresive

Strength3000 psi

Casing Thickness[from tables] .408 in

CBL value for 100% Bond

[minimum expected amplitude]

70% Bond Index ?

CBL value for 70% Bond

Internal Use Only

CBL Calibrations• Prior to running the tool in to the well calibrations

must be performed!• Calibrations are divided into two major categories

– Surface• Master Calibrations• Pre-Job• Post Job

– In Hole• Normalization

• A customers well should never be used to master calibrate a tool unless no other option is available.

Internal Use Only

CBL Calibrations• Gamma Ray

– Calibrate gamma ray using standard Thorium Blanket.• GR Calibrations should be;

– Master calibrated in shop– Pre-Survey conducted on location prior to conducting log– Post-Survey conducted after log is complete

• Acoustics– Each tool will have a series of calibrations that need to be performed

prior to use.– Some tools have more calibration sets than others– Minimum calibration should be;

• Pipe Zero• Pipe Amplitude

Internal Use Only

CBL Calibrations

• Acoustic Calibrations cont.– Calibrations should be performed in a calibration fixture or in

a test well.– Calibrations performed in a client’s well are normalizations.– Perform CBL Air calibrations with suspended in air and not

making contact with any object.

Internal Use Only

Internal Use Only


Radial Cement Bond Tool

Internal Use Only

Radial Bond Log • CBL with sectored receivers

• Provides Information on Radial Continuity of Bonding or Channels.

• Amount of receivers and spacing will be tool dependent.

• Sectored receivers location (Distance from transmitter) will also be tool dependent.

Internal Use Only

2 ¾” PROBE RADIAL CBL TOOL

TRANSMITTER

3 FT RECVR5 FT RECVR

CCLGR

3 FT RECVR DIVIDED IN TO 8 SEGMENTS COVERING 45 DEG SECTOR EACH.

Internal Use Only

RCBL Receiver Placement• Radial Cement Bond Tools Receiver Configuration differs

between manufacturer’s.– Probe Tool- The segmented receivers are placed at the three

foot interval and the CBL Amplitude curve is a calculated average of the segmented receivers.

– CSS and Tekco Segmented Bond Tools have a separate receiver portion of the sonde located 2 foot from the transmitter that provides the radial image.

• It is important to note that if the radial mapping receivers exist as a separate portion of the sonde then travel time for these receivers will be less than the calculated 3 foot TT.

Internal Use Only

RCBL Gate Settings• The process of setting the gate for E1 of three foot receiver signal

remains the same as Dual Receiver Tools, however, the gates for the individual segments must be set on appropriate E1 respectively.

• Dependent on the tool the receiver placements will be a varying distance from the transmitter. Therefore, gate placement will have to be recalculated from the base TT measurement based on the distance from Transmitter to Receivers.

• Example: CSS 1 11/16” Bond Tools Radial Receivers are located 2 feet from the transmitter. Therefore, there is one foot less of steel casing for the sound wave to travel before reaching the receivers. Recalculation for appropriate gate settings would be:– 3’TT – 57uS = Radial 3’ Amplitude Gate Open– Gate width will remain the same as will the threshold level.

Internal Use Only

2 3/4” RCBL TOOL What is the data collected by RCBL ?• 3 ft waveform • 5 ft waveform ( MSG waveform ) • 8 waveforms for 8 segment receivers • calibration waveform • Travel time and Pipe amplitude comes from 3 ft and MSG

comes from 5 ft signal

Internal Use Only

Standard CBL-MSG Presentation

•Includes;•GR, CCL, 3FT Amplitude, Travel Time, MSG• Pipe Amplitude is driven by omni-directional receiver which only displays the sum of the waveform energy received.

Internal Use Only

Radial Mapping Image

•8 Radial Mapping Receivers•Allows for greater definition of pipe bond by directionally receiving the pipe amplitude signal.

Internal Use Only

Comparison

Internal Use Only


Log Header

Internal Use Only

10/14/01 @ 03:30

2840 72250 Sks

Class A 14.72 % Gel

Fresh 11.5 ppg

Primary

Internal Use Only

CompanyWell Name

Date and Time Logged

Depth per Logger

Bottom Hole Temperature

Bit Sizes used Sizes of casing run

Internal Use Only

Type and density of fluid in Casing

Top of Cement

Quantity, weight, and type cement pumped

Date & Time Cement Job10/14/01 @ 03:30

250 SksClass

A14.7

2 % GelFresh 11.5 ppg

Primary

Type and weight of displacement fluid

Other Services Run when Bond Log generated

Internal Use Only

Header (Equipment & Logging)

Internal Use Only

Header (Equipment & Logging)

Explanation of unusual events during logging

Was pressure applied while running the log?

Internal Use Only

COMMON ACRONYMSTravel Time….TT…TT2…TT3…SRT..E1 TTCollar Locator….CCLGamma Ray….. GRPipe Amplitude…SA2Bond Index….BIMicro-Seismogram… VDL…MSG..SpectrumCasing Thickness….THAVMaximum Impedance….ZMAXMinimum Impedance….ZMINAverage Impedance….ZAVG… AVE ZDeviation….INCL.. DEVRelative Bearing….RB… REL BEAREccentricity….ECTYOvality….OVALMud Impedance…MUD IMPEDCaliper…CALIBorehole Volume…BHVAnnular Hole Volume….AHV

3_principle of measurement2

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