This document provides an overview of cement bond logging (CBL), which is a well logging technique used to evaluate the integrity of cement bonding between casing and borehole walls. It works by transmitting acoustic waves through the casing into the cement and detecting reflected signals to analyze bonding. Good cement bonding is indicated by low amplitude signals and strong formation reflections on the logs. CBL is important for assessing cement fill quality, casing integrity, and identifying potential fluid migration paths. It provides a cost-effective way to evaluate cementing operations and design remediation if needed.
CBL was firstly design in 1960’s .
In the beginning only single transmitter and single receiver is used for amplitude measurement .
Then after evolution occurred , just like openhole acoustic log , new design introduced , which measured signal amplitude near receiver .
Eventually borehole compensated device , using dual transmitter and dual receiver were introduced in 1980’s .
CBL was firstly design in 1960’s .
In the beginning only single transmitter and single receiver is used for amplitude measurement .
Then after evolution occurred , just like openhole acoustic log , new design introduced , which measured signal amplitude near receiver .
Eventually borehole compensated device , using dual transmitter and dual receiver were introduced in 1980’s .
This slide would teach the well control method during drilling operations, and the shut-in procedure in case of a kick. Please note that shut-in procedure may vary from site to site depending on the equipment available and the site regulations but whatever the situation, this is the general procedure for well control during drilling. Enjoy!
Formation Evaluation project (drill stem test DST)Gehad Alyazidy
What is DST?
DST Advantages and Disadvantages.
Explain the operations of a DST based on a labelled diagram including its pressure vs time plot.
By referring to a case study reported in open literature, explain the challenges facing the O&G companies to obtain reliable test results.
Well Control is very important in Petroleum Engineering and necessary for being able to avoid hazards and controlling them as much as possible. This presentation provides valuable notes, instructions, and information about Well Control.
wireline sampling or testing tools and bore hole televiewer are a formation testing tools.they help in understanding and evaluating the formation fluid ,composition ,rock type(hard or soft),mud cake thickness etc better .FT,FIT,RFT help in bringing out the formation fluid to the surface and test in the laboratory to conduct a detailed study on fluid type.
WELL LOG : Types of Logs, The Bore Hole Image, Interpreting Geophysical Well Logs, applications, Production logs, Well Log Classification and Cataloging
The objective of this project is to investigate the measurement methods while drilling a well and perform a general assessment and comparison on the methods.
Your Score 1420Not bad. Your score means youre slightly bette.docxodiliagilby
Your Score: 14/20
Not bad. Your score means you're slightly better than the average at reading expressions. And research suggests that people can improve their emotion recognition skills with practice. So keep an eye out for our forthcoming empathy training tool, designed to boost your emotional intelligence. Sign upfor our e-newsletter for updates on it.
Drilling Engineering
Class 8
1
Casing
• What is casing?
• Pipe that is API certified for its specific application
• Why is casing set?
• Zonal Isolation when cemented in place
• Casing point selection
• Regulations
• Area Geology
• Formation Pressures
• As the operator, who decides on casing points?
2
Casing
• API casing is available in standard sizes from 4-1/2” to 20” OD
• Usually steel but can be aluminum, fiberglass, stainless steel,
plastic, titanium etc.
• One piece of casing pipe is referred to as a “joint” of casing
• Casing length is dependent on the “range” of pipe
• Range-1: 18-22ft
• Range-2: 27-30ft
• Range-3: 38-45ft
• Casing Threads are defined by the coupling type
• API Threads
• LTC: Long thread coupling
• STC: Short thread coupling
• BTC: Buttress thread coupling
• Semi & Premium Threads
• See VAM Presentation
3
Casing
• Casing Components
• Casing
• Size, Weight, Grade, Threads
• 9-5/8" 53.5# P-110 LTC Rg 3
• See Casing Data Chart
• What is Drift Diameter?
• Pup Joints
• Float Collars
• Float Shoe
• Guide Shoe
• Centralizers
• Baskets
• Scratchers/Scrapers
4
Casing
• Running Casing
• Bales/Elevators
• Power Tongs
• Torque Turn
• Calculate weight and Hookload HL
• Calculate collapse, how often should you fill the pipe?
• Is the pipe taking the proper amount of fluid to fill? CSGcap
• Is the proper amount of fluid coming back to the pits as the
casing is run in the hole? CSGcap & CSGdisp
• Once casing is landed, circulated mud. Calculate B/U
5
Casing
• Centralization
• Vertical Wells
• Never truly vertical, usually spiral
• Typically use bow spring type centralizers
• There are state regulations on centralizer placement
• The shoe is very important to be centralized
• Horizontal Wells
• Balance between too many and not enough centralizers
• Many types: rigid, floating, bow spring, bladed, spiral bladed, etc.
• Centralizer design software can model the well as drilled and suggest
centralizer placement
• High dogleg areas need more frequent centralizers to obtain
sufficient standoff
6
Casing
• Stand-off
• Pipe Stand-off is a major contributor to hole cleaning, mud
removal, and cement quality.
• % 𝑆𝑡𝑎𝑛𝑑𝑜𝑓𝑓 = ൗ𝑊𝑛 𝑅2−𝑅1 ∗ 100%
7
Casing
• Stand-off
• The Stand-off formula results a percentage, where 0% represents
the pipe in contact with the wellbore wall. 100% represents the
pipe is perfectly centered in the well.
• When the pipe is not centered, the wider portions will promote
flow due to less resistance. There can be pockets of cuttings or
mud in the tighter areas causing
This slide would teach the well control method during drilling operations, and the shut-in procedure in case of a kick. Please note that shut-in procedure may vary from site to site depending on the equipment available and the site regulations but whatever the situation, this is the general procedure for well control during drilling. Enjoy!
Formation Evaluation project (drill stem test DST)Gehad Alyazidy
What is DST?
DST Advantages and Disadvantages.
Explain the operations of a DST based on a labelled diagram including its pressure vs time plot.
By referring to a case study reported in open literature, explain the challenges facing the O&G companies to obtain reliable test results.
Well Control is very important in Petroleum Engineering and necessary for being able to avoid hazards and controlling them as much as possible. This presentation provides valuable notes, instructions, and information about Well Control.
wireline sampling or testing tools and bore hole televiewer are a formation testing tools.they help in understanding and evaluating the formation fluid ,composition ,rock type(hard or soft),mud cake thickness etc better .FT,FIT,RFT help in bringing out the formation fluid to the surface and test in the laboratory to conduct a detailed study on fluid type.
WELL LOG : Types of Logs, The Bore Hole Image, Interpreting Geophysical Well Logs, applications, Production logs, Well Log Classification and Cataloging
The objective of this project is to investigate the measurement methods while drilling a well and perform a general assessment and comparison on the methods.
Your Score 1420Not bad. Your score means youre slightly bette.docxodiliagilby
Your Score: 14/20
Not bad. Your score means you're slightly better than the average at reading expressions. And research suggests that people can improve their emotion recognition skills with practice. So keep an eye out for our forthcoming empathy training tool, designed to boost your emotional intelligence. Sign upfor our e-newsletter for updates on it.
Drilling Engineering
Class 8
1
Casing
• What is casing?
• Pipe that is API certified for its specific application
• Why is casing set?
• Zonal Isolation when cemented in place
• Casing point selection
• Regulations
• Area Geology
• Formation Pressures
• As the operator, who decides on casing points?
2
Casing
• API casing is available in standard sizes from 4-1/2” to 20” OD
• Usually steel but can be aluminum, fiberglass, stainless steel,
plastic, titanium etc.
• One piece of casing pipe is referred to as a “joint” of casing
• Casing length is dependent on the “range” of pipe
• Range-1: 18-22ft
• Range-2: 27-30ft
• Range-3: 38-45ft
• Casing Threads are defined by the coupling type
• API Threads
• LTC: Long thread coupling
• STC: Short thread coupling
• BTC: Buttress thread coupling
• Semi & Premium Threads
• See VAM Presentation
3
Casing
• Casing Components
• Casing
• Size, Weight, Grade, Threads
• 9-5/8" 53.5# P-110 LTC Rg 3
• See Casing Data Chart
• What is Drift Diameter?
• Pup Joints
• Float Collars
• Float Shoe
• Guide Shoe
• Centralizers
• Baskets
• Scratchers/Scrapers
4
Casing
• Running Casing
• Bales/Elevators
• Power Tongs
• Torque Turn
• Calculate weight and Hookload HL
• Calculate collapse, how often should you fill the pipe?
• Is the pipe taking the proper amount of fluid to fill? CSGcap
• Is the proper amount of fluid coming back to the pits as the
casing is run in the hole? CSGcap & CSGdisp
• Once casing is landed, circulated mud. Calculate B/U
5
Casing
• Centralization
• Vertical Wells
• Never truly vertical, usually spiral
• Typically use bow spring type centralizers
• There are state regulations on centralizer placement
• The shoe is very important to be centralized
• Horizontal Wells
• Balance between too many and not enough centralizers
• Many types: rigid, floating, bow spring, bladed, spiral bladed, etc.
• Centralizer design software can model the well as drilled and suggest
centralizer placement
• High dogleg areas need more frequent centralizers to obtain
sufficient standoff
6
Casing
• Stand-off
• Pipe Stand-off is a major contributor to hole cleaning, mud
removal, and cement quality.
• % 𝑆𝑡𝑎𝑛𝑑𝑜𝑓𝑓 = ൗ𝑊𝑛 𝑅2−𝑅1 ∗ 100%
7
Casing
• Stand-off
• The Stand-off formula results a percentage, where 0% represents
the pipe in contact with the wellbore wall. 100% represents the
pipe is perfectly centered in the well.
• When the pipe is not centered, the wider portions will promote
flow due to less resistance. There can be pockets of cuttings or
mud in the tighter areas causing
RESTORATION OF EXISTING MAJOR BRIDGE ACROSS RIVER BHADAR ON NATIONAL HIGHWAY ...IEI GSC
By S.K.Patel, P C Gandhi S R Shah J N Prajapati
at 31st National Convention of Civil Engineers
organised by
Gujarat State Center, The Institution of Engineers (India) at Ahmedabad
Uses of special kind of technologies for implementation of special kind of st...Rajesh Prasad
The said technical paper was presented by Rajesh Prasad in IC TRAM 2018 (International Conference- Technological Advancement in Railways and Metro Projects at Manekshaw Centre New Delhi on 04.10.2018
Self-compacting concrete (SCC) is considered as a concrete which can be placed and compacted under its own weight with no vibration.
It is not affected by the skills of workers, the shape and amount of reinforcing bars or the arrangement of a structure.
Due to its high-fluidity and resistance to segregation, it can be pumped longer distances.
It consists of the same components as conventionally vibrated concrete, which is cement, aggregates, and water, with the addition of chemical and mineral admixtures in different proportions.
Usually, the chemical admixtures used are superplasticizers and viscosity-modifying agents.
SCC is especially useful in confined zones where vibrating compaction is difficult.
(mr. akash kolamkar) Rajapeth ROB Flyover seminar amravati an detailed struct...Bharat Badre
rajapeth rob is an bridge in amravti if want soft copy of file with report also write me at akashkolamkar@gmail.com ,,,, iam engineer of project ,, so i will try to explain all points wit h reports ,,, now am a student of engineering so i completelly know need of seminars
i am akash kolamkar ,in my city amravati maharashtra india ,, in my city amravati a biggest bridge structure is going to construct so i have an idea to make it useful for others,,, in this report i will explain all concept with detailed drawing presentation ,, because i am engineer of project with college student if want soft copy of that file with report also so, u can mail me at akashkolamkar@gmail.com
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
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How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
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.
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.