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Cement Bond Log
- 1. NURUL ANISAH BINTI HAJI IBRAHIM DIPE06/16/0618 1 CEMENT BOND LOG (CBL) PE4301 PETROPHYSICS & WELL LOGGING:
- 2. OUTLINE ● INTRODUCTION ● APPLICATION ● PRINCIPLE ● INTERPRETATION OF CBL ● IMPORTANCES 2
- 3. CEMENT INTEGRITY LOGS 3 CEMENT BOND LOG (CBL) CEMENT MAPPING LOG (CMT) ULTRASONIC CEMENT MAPPING TOOLS (CET) ULTRASONIC IMAGING LOGS (USI, BRT)
- 5. INTRODUCTION 5 ● Measures the integrity of cement bond between tubing/casing and well bore. ● The log is typically obtained from a sonic tool which detects the bond of the cement to the casing and formation via a principle based on resonance. ● Documents an evaluation of the integrity of cement work of a well. It is done after the cement are set properly in the well.
- 6. 6 ● Cement bond logs are used to detect the presence or absence of external cement behind casing. ● Proper cement placement between the well casing and the formation is essential: 1. To ensure mechanical support of the casing. 2. Protection from fluid corrosion. 3. Isolation of permeable zones at different pressure regimes to prevent hydraulic communication. 4. Prevent fluid from leaking to the surface. APPLICATION
- 7. 7 ● A sonic tool is typically run on wireline. ● Transmitter sends acoustic wave to casing/cement. ● Receivers receive acoustic signal that transfer through casing to cement and reflects to receivers. ● Acoustic wave at receivers is converted to amplitude (mV). PRINCIPLE
- 8. 8 A typical cement-log presentation includes: ● A correlation curve (gamma ray), travel time (μsec) ● Amplitude (mV) ● Attenuation curves ● A full-waveform display. INTERPRETATION OF CBL
- 9. 9 INTERPRETATION OF CBL GOOD CEMENT · “Amplitude” low. · “VDL” formation signals are strong. · Good cement. No need for squeeze • Casing that is not bound has a higher resonant vibration than that which is bound, causing the imparted energy from the sonic signal to be transferred to the formation. In this sense, the amplitude of the waveform received is the basic measurement that is evaluated.
- 10. 10 IMPORTANCE ● Determine the quality of the cement bond to the casing. ● Evaluate cement fill-up between the casing and the reservoir rock. ● Measure the compressive strength of the cement, the bond index, and in some cases, the quality of the casing string itself. ● Relatively inexpensive and almost every wireline company has a version of the tool.
- 11. THE NAME IS BOND, CEMENT BOND. THANK YOU!
- 12. 12 REFERENCES ● https://www.spec2000.net/07-cementlog1.htm ● http://petrowiki.org/Cement_bond_logs ● https://en.wikipedia.org/wiki/Cement_bond_log ● http://www.drillingformulas.com/what-is-cement-bond-lo/ ● http://www.slb.com/~/media/Files/production/product_sheets/well_integrity/cement_bond_logging_tools.pdf ● http://www.slb.com/services/drilling/cementing/cement_evaluation.aspx ● http://www.bridge7.com/grand/log/gen/casedhole/cbl.htm ● https://www.linkedin.com/pulse/bond-cement-bonda-quick-guide-reading-cbl-william-fogerty ● http://www.kdheks.gov/geo/download/seminar_2015/5%20Workshop%20-%20Leeth%20-%20cement- bond%20logs.pdf ● https://higherlogicdownload.s3.amazonaws.com/SPE/5fc0079d-67a5-4dd9-a56f- 190534ef5d3d/UploadedImages/April16_BtoB.pdf
Editor's Notes
- CBL is providing a global response to the cement/material present in the annulus, it is a qualitative measurement of the bond index but it is difficult to make an assessment related to a potential channel. it is considered that a Bond index above 80% along a minimum length function of the casing size means a good isolation, but 80% means a channel of 20% i.e 72 ! VDL is associated with a CBL ( as SBT, etc..) it is the only conventional tool allowing to get a qualitative indication of the bond with the formation. USIT is providing an image of the cement in contact with the casing surface. In contact, that means only few millimeters of cement. Today another tool is available from Schlumberger ,the Isolation Scanner . It is an ultrasonique tool , it can provide an indication of the material behind the casing (solid , liquid or gas) as an oriented VDL. In some cases, you can get an image of the interface between cement and formation. this tool is allowing to log low impedance, low density cement. You can found a lot of informations related to cement logging tools in the API Technical Report 2. Simplistically the CBL VDL is an acoustic frequency signal. It measures a change in amplitude between a receiver and a Transmitter. It is a good average indicator of cement quality, but will not give any understanding of gas cut cement,microannulus, and channels of unwanted fluids ie whether there is a potential of communication. The USIT tool works in the Ultrasonic range and by measuring attenuation by varying angles of inflection, not only can channels be seen, and Gas cut cement determined. If run in combination with a CBL - VDL even more information is known especially about gas cut cement, fluids occupying microannulus or channels. Obviously this is very important in understanding the effects of drilling / cementing practices making repairs to a well or changing future practices. It is very common for companies who have a good understanding on the integrity of the cement sheath and are in known areas to only run a CBL VDL. This is more likely on Shallow wells with one String of Casing. However, if you have wells with risks to communication due to underlaying water, gas. Also I might add that wells with liners are far more likely to communicate than others. Another issue is that, though many cement jobs are far from perfect communication does not occur. Knowing thisand depending oncircumstances I would not attempt a repair. Unlike log interpretation cement evaluation is not an exact science. However, if the well has a very high potential andwhere a workover would be very expensive to performyou may want to attemptduring the completion. The other situation is if the cement job is very bad and a channel is all the way to surface though this with todays practice unlikely. I mention this in passing becausein the early development of the CET which is the precursor to the USIT log I was shown a set of logs. Ihedged mywords knowingthegrey areasof interpretation and said there is a high likelihood the well was channeled to surface. The operator knew something I did not know and that was the well had blown out to surface. Due to hydrostatic head mud contamination etc. the well appeared at first to have integrity. A good strategy is to run the USIT over zones or risk and then the CBL VDL back to surface. If it is a first well in the program it may be wise to run the USIT to surface. Depending on risk CBL VDL may be only required on upper casing strings. It all depends on the risks that exist and how good your cementing practices are. To identify zones of potential your petrophysicist should be able to help you. Hole rugosity also an issue and you can use a caliper log to judge this. There is not a straightforward answer to this but if you would like to discuss it further it would be better to discuss more off line.
- The newer versions, called “cement mapping”, can give detailed, 360-degree representations of the integrity of the cement job, whereas older versions may display a single line representing the integrated integrity around the casing. Cement needs to set properly before a cement integrity log is run. This can take from 10 to 50 hours for typical cement jobs. Full compressive strength is reached in 7 to 10 days. The setting time depends on the type of cement, temperature, pressure, and the use of setting accelerants. Excess pressure on the casing should be avoided during the curing period so that the cement bond to the pipe is not disturbed. A cement bond log documents has an evaluation of the integrity of cement work performed on an oil well.[1] In the process of drilling and completing a well, cement is injected through the wellbore and rises up the annulus between the steel casing and the formation.[2] A sonic tool is typically run on wireline by a service company that detects the bond of the cement to the casing and formation via a principle based on resonance. Casing that is not bound has a higher resonant vibration than that which is bound, causing the imparted energy from the sonic signal to be transferred to the formation.[citation needed] In this sense, the amplitude of the waveform received is the basic measurement that is evaluated. The data is collected by the tool and recorded on a log which is used by the oil producing company as an indicator of zonal isolation in the well. There are production reasons and legal reasons (governed by a petroleum regulatory body in each individual state) that dictate the well must have specific areas of isolation. Cement Bond Logging (CBL) A standard CBL (Cement Bond Logging) tool uses sound energy to determine how well bonded the cement is to the casing. It is affected by the compressive strength of the cement with higher compressive strengths giving higher attenuation and larger percentage of bonded pipe giving higher attenuation. It works by making sound! Electricity/voltage is applied to the transmitter which emits sounds (it will vibrate at a particular frequency) like a tick clock! The noise on your watch! The noise then travels through the casing, between casing and formation (hopefully it is filled with cement) onwards to the formation. Then travels down to the receivers where it vibrates and produces and electric signal (just like the receiver but in reverse!). So what they are measuring is 1) the time it takes the sound to travel 2) the amplitude (the loudness of the sound when it returns to them) and 3) how many different signals did they get back. The receivers are spaced out from the transmitter. One at 3ft and the second one at 5 ft. The reason for this is to give them a better resolution. Get rid of background noise. Empty vessels make more noise!! No cement, the amplitude is high
- Both poor bond and poor fill-up problems can also allow fluids to flow to other reservoirs behind casing. This can cause serious loss of potential oil and gas reserves, or in the worst case, can cause blowouts at the wellhead. Poor bond or poor fill-up can often be repaired by a cement squeeze, but it is sometimes impossible to achieve perfect isolation between reservoir zones. - Squeeze cementing, sometimes referred to as remedial cementing is an operation designed to force cement into leak paths in wellbore tubulars. The required squeeze pressure is achieved by carefully controlling pump pressure. Squeeze cementing is a “correction” process that is usually only necessary to correct a problem in the wellbore
- A sonic tool is typically run on wireline by a service company that detects the bond of the cement to the casing and formation via a principle based on resonance. Casing that is not bound has a higher resonant vibration than that which is bound, causing the imparted energy from the sonic signal to be transferred to the formation. In this sense, the amplitude of the waveform received is the basic measurement that is evaluated. The concept is likes when we knock pipe. If there is something coverage around pipe, the reflection sound will be attenuated, and vice versa. When the acoustic wave generated by the transmitter reaches the casing, Part is refracted down the casing (amplitude and travel-time measurement) Part travels through the mud (fluid arrival) Other parts are refracted into the annulus and the formation and received back (formation arrival) Amplitude, measured directly or as an attenuation ratio, is the primary bond measurement and is used to provide: Quantitative estimations of cement compressive strength Bond index Qualitative interpretation of the cement-to-formation interface It works by making sound! Electricity/voltage is applied to the transmitter which emits sounds (it will vibrate at a particular frequency) like a tick clock! The noise on your watch! The noise then travels through the casing, between casing and formation (hopefully it is filled with cement) onwards to the formation. Then travels down to the receivers where it vibrates and produces and electric signal (just like the receiver but in reverse!). So what they are measuring is 1) the time it takes the sound to travel 2) the amplitude (the loudness of the sound when it returns to them) and 3) how many different signals did they get back. The receivers are spaced out from the transmitter. One at 3ft and the second one at 5 ft. The reason for this is to give them a better resolution. Get rid of background noise. Empty vessels make more noise!! No cement, the amplitude is high
- A sonic tool is typically run on wireline by a service company that detects the bond of the cement to the casing and formation via a principle based on resonance. Casing that is not bound has a higher resonant vibration than that which is bound, causing the imparted energy from the sonic signal to be transferred to the formation. In this sense, the amplitude of the waveform received is the basic measurement that is evaluated.
- The Cement Bond Log (CBL) gives a continous measurement of the amplitude of sound pulses from a transmitter to receiver. This amplitude is maximum in unsupported pipe and minimum in well-cemented casing. The wave train can be displayed as a Variable Density Log (VDL) where the positive and negative cycles of the wave train are shaded black and white respecticvely.