No matter the industry or endeavor, we all learn through experience. Some discoveries are surprising, it’s easy for us to make assumptions, and often things work despite our errors. Ironing out any misconceptions about cementing means that we can follow best practices and minimize margins of error.
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Something for the group to enjoy.
Who can identify the most important misconceptions about cementing?
Below, we can find some clues:
Zonal isolation: Knowing the role of probability here?
Cement placement: How is the cement actually flowing?
Cement evaluation: What are we actually seeing in a cement log?
Sometimes, good cement jobs are the result of careful planning, and others are just mere luck.
Matteo Loizzo Lenin, you got me curious: you seem to have an answer up your sleeve.
Regardless, here are some mixed opinions:
* If with probability you mean uncertainty, then: yes, a huge role. We don’t know a lot and sometimes are ignoring essential factors because they don’t fit our pre-packaged simulators. If you want to be pedantic, big time epistemic uncertainty and not much aleatoric unc.
* Given the long and thin spaghetti well, cement flows +/- independently along the three directions: axial you have fluid mixing, azimuthal you have channeling and radial (annular thickness) you have. Many hypotheses (e.g. mud-on-the-wall, slurry particle gradients) but minimal practical effect anyway.
* Logs are reasonably predictable, with few remaining mysteries – that is, if you have some ideas about how cement behaves.
Now your turn. This promises to be an interesting conversation.
Bryan Simmons Simulations give good information on how a system will behave as its being pumped. Good data is critical to any cement job and affects the accuracy of the simulation. Designing for the well conditions is also critical. A one size fits all philosophy won’t work on critical wells. Communication between the customer and the service company is another key element for a successful cement job. Losses, weak frac gradients, high viscosity MUDs, deviation, etc., all contribute to the success or failure of a cement job. The old pump it and bump it mentality went out the window after the Macondo disaster.
It takes careful planning, operational performance, sound engineering and constant communication to perform a critical cementing project. If you do all of the above, you still can’t guarantee a successful job but you can help ensure that everything was done to satisfy the criteria of zonal isolation, good bonding and a successful cement job.
Dan Ryan Taking the “low bid” on a land-based surface casing cement. “It’s only the surface casing – what difference does it make?” It’s like the foundation of a building you only get one shot at doing it right and if mess it up have problems from now on.
Tim Graham Well I know the number one determining factor; is mud removal……..
Jim Beddow I believe one of the biggest misconceptions is that cement slurries must be in turbulent flow to be effectively placed. Flow regimes are overrated. Centralize your pipe and ensure enough contact time with your spacers and you’ll get good isolation whatever your presumed flow regime turns out to be.
Jim Irsik Biggest misconception: Cement will not set if pumped in daylight.
Michael Mehle On the more practical side, ultra-high compressive strength is not necessarily a good thing, particularly in completion zones. For most completion cements, 1000 psi compressive strength is more than enough to provide durable zonal isolation. 3000-4000 psi compressive cement tends to be difficult perforate and frac through and is far more brittle than a comparatively lighter duty slurry.
G. Barry Evans Lowering of the PV and YP of the mud is critical to ensuring proper mud removal and cement placement. I have seen many post cement CBL’s on wells where the YP and PV of the mud were high.
Drew Hoppe, All of the above, is all well and good, then everyone is happy for the Slurry hand to do the job with only a trainee helper and God forbid should he waste 5 minutes.
james cottom It is impossible for a cement crew to pass a mini-mart or café on the way to a job without stopping…
Veronica Breto Biggest misconceptions for a cement plug… I only need 50 ft, so let’s plan for 100 ft to be sure we are going to tag it…
Don Purvis Let me add one:
We suffer under the delusion that the way we test cement tells us how the cement will behave in a wellbore. I am currently in India on an SPE DL tour talking about cement testing verses wellbore reality. So far no-one has disagreed. The basic tests we have used for years do not reflect how the cement will behave in the wellbore. It is time for a paradigm shift.
Buck Iles Well stated Mr. Beddow.
Rick Eyler Rain shine snow or sleet. We’ll be there after we eat.
Bryan Simmons Misconceptions? Hole conditioning isn’t necessary, don’t need centralizes, pump as fast as you can, don’t use wiper plugs, use the cheapest cement you can, cement simulations aren’t necessary, etc. I’m sure there are a lot more, but ALL of these will compromise a cement job.
james cottom A company man once told me that additives weren’t necessary… He could control pump time by adding more or less water. I guess that is somewhat true but what a can of worms!
Tommy Brennan Guys, Some good points made and few additional things to note, perhaps.
All primary cement jobs need / want / like us to:
1. Drill a round, in gauge, hole;
2. Have the pipe correctly centralized in open hole AND cased hole;
3. Minimize and homogenize the drilling fluid rheology & density.
4. Pump both chemical wash and spacer ahead of scavenger slurry;
5. Use three plugs, where possible (protect spacer as long as possible);
6. Move the pipe during all pumping – both reciprocation and rotation;
7. With cement in place and set, tell loggers the acoustic impedance of lead and tail slurries (they will not be the same)
8. Finally – I strongly support the statement on how poor our API approved slurry testing is. Cement sheaths often fail in shear and tensile loads, for instance, (think frac jobs). Compressive strengths can be an indicator of mechanical properties, but what we should look at is Poissons Ratio and Youngs Modulus.
Just my 2 cents worth.
Blessing Adaka There’s no need to calculate the rat hole volume because the slurry will always U-tube. Trust me, this rate hole should be kept at a minimum and to trap contaminated cement.
James Cottom I think the biggest misconception is that service companies are trying to upsell with high-tech designs. On critical cement jobs ( how do you decide which aren’t) where zonal isolation is most important, it becomes challenging to weigh the variables in terms of importance to success. In the late ’90’s we had access to 1000’s of primary jobs in GOM, and we evaluated the various designs to attempt to determine which of the variables or methods yielded the best jobs.
It became clear that no single approach or procedure or combination of a few best practices was more or less critical than the others as stand-alone methods. What we discovered instead was that the more best practices and proven methods employed, the more likely a good quality cement job would result. The bottom line is to do all you can to enhance the chances of success. Drill a good hole, remove the gelled mud from the hole, centralize the pipe, move the pipe, run plenty of shoe track, run two plugs. Don’t scrimp on the cement job.
Mustafa Kadhim One of the biggest mistakes is reading CBL’s or any bond evaluation log without running a cementing simulation with the actual: job Rates; borehole fluids properties; actual mud conditioning time and rate; centralizer as per pipe tally; accurate caliper ID for the hole. (Clients usually jump to the conclusion the cement is bad, which is not right most of the time).
Tim Graham Last one (8) is new to me Tommy. Cant support it but my thoughts would be the opposite. I agree testing is a poor indicator of final strengths but cement will borrow strength from surrounding formation and or casing.
Andy Tynes Brian is right and the luck part you are very wrong about that statement. You talk like you need a lot of training and insight on the question you ask because you have it all wrong.
Muhammad Alam from design till execution every step is essential. Small mistake impacts on evaluation. Sure high displacement rate can help a lot.
Tim Graham What was the purpose of all this?
Gary Batcheller I am a logging guy, but always put together the facts to see what affects or is it effects? The log and over the years I can assure all of these things make a difference and where we HAVE fallen down the most is on the spacer (too often not enough) and mud conditioning and standoff (not centralization).
Finally, on testing cement remember all we have come from the construction business where it’s essential to have enough compressive strength to put a building on top of, but we are not putting buildings here, and cement likely fails in a different mode in our circumstances.
Neda Ahmadpour when a cement job results goes wrong, you can easily say its from centralization (especially in off-shore that one shot in the sea and one in the hole!), or you can point to a bad well condition or direction. The funny part is when the client puts the log in front of you, for liner lap (CBL/VDL doesn’t show CSG/CSG)sometimes fast formations helps as well 🙂
Neda Ahmadpour This may help you as well: ISSN 2305-8269
Adrian Garcia there is no luck in a successful cement job when considering all essential points to execute a job. Knowledge the Background, logs evaluation, formations, cementing simulations. Including all these points is not a matter of luck. In the case of other conditions in well. Have to consider to do a whole different job, and redesign your cementing job.
Bimal Bhattacharya Considering that all aspects of good cementing practices have been incorporated at the planning stage and executed in the operation stage; it is important to look at the qualitative aspect of cement slurry design. Often it is seen that the slurry design finalized in the lab and confirmed by the simulation do not match with the slurry prepared and pumped during the operation. This deviation is often overlooked in cement evaluation and that could be the main reason for a misleading/mistaken conclusion.
Gary Batcheller Consider that not only cement mixture may be different but likely not remove mud completely And cement mud mixture will look different and is miss interpretation and yet is. Solid and impermeable hence provides isolation.
Will Butler, P.Eng All great points, but over thought on many things such as the difference in cement from simulation, lab to field. If all are diligently recreated, there is negligible impact on cement failure once placed in the wellbore. 90% of issues seen are a combination of drilling practices AND mud displacement and proper slurry design. First thing I look at when analyzing a wellbore issue is the drilling report.
Abdelhamid Ouzane Good evening gents. In my opinion to get good cement results to start from drill a good hole with acceptable wash out. Centralization with Acceptable standoff then slurry design and operation execution.
Jerry Browning Pumping at eight bpm will put all fluids in the annulus in turbulent flow. This is just what the folks on the cementing unit think.
Christoph Duwe Hi, I am new to this group, and so please forgive me if my contribution is misplaced or inappropriate. I am involved in the ultrasonic testing of setting processes of cement, concrete and other materials that have a setting process.
Through the ultrasonic sound velocity, it is easy to precisely measure the growth of material strength and the e modulus. So far, big companies such as e.g. LafargeHolcim, have equipped many of their European labs and plants, but to my knowledge, there has not been an approach by (or to) oil industry.
Is this because we failed to contact the right people or is a precise measurement of the slurry behaviour not required? I have no experience in this field of operation, but I can imagine, that measuring the actual action of the cement and additives in situ should be a benefit, regardless of other a.m. influences such as mud etc.
I am curious.
Jerry Browning Christoph, go online to Chandler Engineering – Oil Well Cementing – Compressive Strength.
István Onozó Compressive strength referred here as measured by UCA/SGSA.This is also another misconception that people believe that the slurry sets as per the graph but in reality, if you repeat the same test at the same conditions you get different results and the variation is even more for SGS. It all comes down from the fact that so many variables in the lab as well as on the field. Misconceptions are based on that we believe that we can control everything.
Bimal Bhattacharya Christoph, ultrasonic testing is already in use for the cement slurry in planning and post-operation analysis stages.
Christoph Duwe Bimal, this is quite interesting. Do you have a price indication?
Christoph Duwe Sorry, I meant Jerry …
Christoph Duwe István, the development of compressive strength in a setting process strongly correlates to the ultrasonic sound velocity across the material. The repeatability of such ultrasonic measurements is usually very high. This is a reason why it is well used in the lab environment for recipe development. Do you mean that this is not the fact in general or just concerning the a.m. measuring devices?
Christoph Duwe Bimal, who are the manufacturers of the ultrasonic test systems that you mentioned?
István Onozó Christoph, The algorithm being used by the UCAs are developed for pure cement slurries which correlate well with cements. ( 1-2 hours variation) Nowadays we are using exotic materials for making cement blends. These materials effects on the transmission of the ultrasonic waves hence give different results. I have seen hours of difference in setting or not shown any setting at all while the cement was hard.
Variation of the results can come from other factors as well ( how the slurry was preprepared, conditioned, set the correct pressure on the machine, select the proper algorithm etc..). There is a variation also between different devices and between different manufacturers.
Christoph Duwe István, thank you for your information. I am a little bit surprised because of the algorithms being used. Our ultrasonic systems measure the ultrasonic sound velocity across the specimen. This velocity usually directly corresponds to the E modulus and the compressive strength of the material under test. Our applications are generally labs of R&D or QA or, with our mobile device, construction areas (buildings or roads/bridges).
Up to now, we did not deal with pressure applications, and a significant issue (and experience) is eliminating noise that could cover or otherwise affect the real signal. As I mentioned before, we did not have access to oilfield applications yet, but apart from that our products are used throughout many industrial applications around the globe, including all kinds of additives. Maybe I am wrong, but would possible algorithms be used to simulate the situation in situ at the oilfield (high pressure/temperature)?
István Onozó Christoph, Ultrasonic Cement Analysers ( UCA’s) measure the compressive strength continuously. So you are right the measurement is in situ at the given downhole conditions as it is determined by measuring the change in velocity of an ultrasonic signal transmitted through the cement specimen as it hardens. As the strength of the cement specimen increases, the ultrasonic signal’s transit time through the sample decreases.
Using proprietary algorithms that have been proven throughout the industry, the relative strength is calculated and a graph produced.S tatic Gel Strength Analysers (SGSA’s) are modified UCA’s where a separate algorithm is used to calculate SGS and Compressive Strength simultaneously at downhole conditions.
The advantage of these machines that you can see the compressive strength/ gel strength at the given time. In oilfield operations, it is important to know how long it will take to reach specific compressive strength values for drilling continuity.
István Onozó Main manufacturers: Chandler, OFITE, Fann, CTE
Bimal Bhattacharya Christoph, please refer to details of manufacturers as mentioned by István. They supply to the cementing service companies and also to the operating companies who have set up cement test labs.
Bimal Bhattacharya On one side UCAs measure the strength of the set cement in the lab, on other side logging tool like USIT measure the strength and status of set cement behind the casing in the well where it is placed.
Madan Mohan The greatest misconception about cementing is nothing else but it’s evaluation. Most of the time cement bond evaluation is contradicting & conflicting, not only with cementers but also with the logging experts. My long experience with cement job & cement bond evaluation reveals that people have their own concepts about the evaluation through cement bond logs which needs to be clarified to remove their misconception for proper understanding & interpretation of cement bond logs.
Still, people evaluate the cement bond seeing only the CBL amplitude line & straight away jump to the conclusion on cement bond. Few are there who say that USIT is showing good bond but CBL is showing poor. Moreover, their is every possibility for a log to be an invalid piece of information for certain QA & QC reasons, which need to be examined at the beginning itself. Surprisingly, it is rare to declare a log invalid & not paid for quality assurance in recording & presentation. Time to improve knowledge on logs.
George Walker After a liner job a whole micro annulus was shown up on the bond log from shoe to liner top what a disaster, it took a cementer i.e. me after spending thousands of pounds to tell them that the micro annulus was the plastic coating on the outside of their pipe. What killed the oilfield Engineers & O-rings
Brett Levy One of the most important aspects of ensuring effective cement placement is convincing your client to run the necessary amount of centralizers and/or casing rotation. Besides other variables (wash out, thief zones, etc.), sufficient centralization will result in achieving optimal cement placement the majority of the time. (We still need proper cement slurry design and volumes obviously on a case by case basis)
George Walker, the worst thing about this site 90% of you, could not even tell what colour concrete is.
Lenin Diaz That is actually the best thing?
Paul Wilkinson I know Lenin quite well having worked with him for some time, What this guy does not know can be written on a postage stamp, he is sooooo knowledgeable he can run circles around most cementers I know.
Do you have anything to add? We’ve covered all the misconceptions about cementing that we could think of, but did we miss anything? Please add to the conversation below. Thanks!