• Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • Primary Cementing
  • Remedial Cementing
  • Plug Cementing
  • Job Execution
  • Post-job results interpretation
  • Equipment
  • Laboratory
  • Mission
  • About
  • Contact and Questions?
  • My Cementing Challenges

Better Well Cementing for ALL

The Leading Online Support Hub for Better Oil Well Cementing.

Cement Slurry Mix Design Decision Tree

April 7, 2017 By Lenin Diaz 12 Comments

Cement Slurry Mix Design Decision Tree

The optimal cement slurry mix design principle

There is a principle that I have always come to appreciate when talking about designing cement slurries. This principle is easy to remember: ‘the simpler, the better’. In this context, this means the use of the less possible additives, in their lowest effective concentration, that can provide the desired cement slurry features.

We base the principle on the assumption that there is a level of interaction* between all the components in a cement slurry. So, by reducing the number of elements and their concentration, the side effects would be minimized.

However, sometimes this is not that easy. The cement slurry mix design formulation would strongly depend on the experience of the laboratory itself (database) and the lab technician.

The flowchart below is a simple point of departure to design conventional cement slurry systems for each well-cementing laboratory.

Depending on workload, experience, availability of quality cement and chemicals, this cement slurry design flowchart is adapted to ensure that we can deploy reliable fluid systems.

(*) Interaction = the balance between desired (targeted) and negative (side effects) reactions.

Cement slurry mix design decision tree


What steps do you take to make corrections in the following cases? 

Please share them in the comments section below

  1. Rheology too Low
  2. Gelation problems
  3. Compatibility Issues (with the mud)
  4. Static Gel Strength too Low (45 min)
  5. Compressive strength Development (too slow) or Max. value (too low)

BONUS: Visible Vortex @ 12000 rpm (blender) = Good surface mixability

https://better-cementing-for-all.org/wp-content/uploads/2017/04/slurry-mixing-small1.mp4

Cheers

L. Diaz

me




 

Related posts:

  1. Cement Slurry design Basics
  2. Workover Cementing Techniques 2: Squeeze Cementing
  3. Cementing Flowchart
  4. Misconceptions About Cementing

Filed Under: Laboratory Tagged With: cement slurry design, FLAC, Free Water, laboratory, Rheology, slurry design, Thickening Time

Article Posted By:

Lenin Diaz is an oil industry specialist with 26 years of technical and operational expertise in fluids, cementing, water control and shut-off. A distinguished track record spanning BP, Schlumberger, and NAPESCO. Lenin lives in Tenerife, Spain and is the creator of this website. Read More…

Reader Interactions

Comments

  1. Valentine Elogie says

    April 10, 2017 at 6:34 pm

    Yes, you are right, some time cement slurry design might be more than just the flow chart above, due to the function and properties of some chemical. Some fluid loss chemical has dual function some time tri-function, In optimizing the additive, the flow chart above will be greatly altered.

    Rheology too Low
    For low rheology, anti-settling agent or gelling additive / some fluid loss additive that has the ability to add viscosity to the fluid need to be used, however, you must strick a balance in optimizing the concentrations, since most of this additive have some negative impact on compressive strength

    Gelation problems,
    This occurs when the amount of dispersant or other chemicals like fluid loss are either too much or too little. The main challenge is to optimize the chemicals.

    Compatibility Issues (with the mud)
    Compatibility measurement is still a subjective issue, that relies mostly on personal judgment than values obtained in rheological figures. However, the values are fundamentals to engineers.

    Compressive strength Development (too slow) or Max. value (too low)
    Many a times slurry are design with too many concentrations of additive than expected. some additive like gelling agent that increase viscosity and improve the rheological properties tend to reduce compressive strenght or delay Cs, again proper optimization is the key to a better cement design. the same principle applies to SGS, so optimization is the key.

    Reply
    • Lenin Diaz says

      April 10, 2017 at 9:12 pm

      Hi Valentine. Great contribution to the topic, certainly very useful to our readers.

      Reply
      • Eric Villepreux says

        April 11, 2017 at 8:45 am

        Agree with you Lenin a very valuable input from Valentine, also an absolute necessity of running the lab tests with the water and cement samples received from the rig prior to the job.
        What I usually do is ask for tests to be ran at the beginning of the project (DWOP) and when I accepted slurry characteristics for each casing job plus a possible plug for every section, final recipe to be fine tuned with the rig samples to take into account any adjustment that may be needed because of possible alterations of the bulks and additives.
        Better safe than sorry!

        Reply
        • Lenin Diaz says

          April 11, 2017 at 11:26 am

          Eric, thanks for this comment, this is experience talking, but also a very nice way to keep all involved in line with the planning. Not only the people in the DWOP, but the rest of the organization, supply chain, inventory, laboratory.

          Reply
  2. Bill Wheelis says

    April 13, 2017 at 5:33 pm

    Review the CHL Web Page http://www.chllogs.com or google Oil Well Cement Evaluation and select the CHL.

    To add the CHL to the Cement Slurry Design Decision Tree with a playback of the CHL Trace and CHL Heading for a Well you are working on, send a pdf file of the main log section, a LAS file with the 3 FT Amplitude and Depth data, the Casing Size, Weight, and the Weight of the Cement. Plus the Well Sketch Data – Well Depth, Casing Depth, Float Collar Depth, and Mud Weight.

    Working together, the CHL could provide In Place Cement Placement and the Cement Placement Patterns, with Measured In Place Cement Curing at the time the Log was run, and provide an additional Visual, Simple, Consistent Cement Evaluation Presentation for the Cement Slurry Design Decision Tree.

    Looking forward to your reply.

    Bill Wheelis

    Phone – 1 – 504 – 393 – 0263

    Reply
    • Lenin Diaz says

      April 14, 2017 at 12:25 am

      Bill, thanks for your contribution. I have seen the website http://www.chllogs.com and I am quite interested. I will send you a message to the email address you provided to discuss further.

      L. Diaz

      Reply
  3. Kedar Sapte says

    April 14, 2017 at 5:05 am

    Hello Lenin, thanks for sharing the info. As usual, it is helpful.

    The slurry design is an optimization process and it needs to take into account the primary as well as the secondary effects of all the additives. Following are the few of my thoughts;

    Rheology too Low

    If the surface RH is too low, it can be improved by adding a viscosity modifier (gelling agent). Many FL additives have the characteristics to increase the RH. However, the real challenge lies in getting good RH at downhole temperature (especially in moderate to HT wells) as excessive thermal thinning of the slurry may compromise the rheological hierarchy. The cementing additives fail to provide the necessary body to slurry at high temperatures. In such a scenario, adding some cementitious solids to the slurry (extenders) helps. This results in increasing solids to liquid ratio. However, this may require adding extra retarder.

    Gelation problems

    This may particularly be attributed to the reactivity of the cement. Also, adding too much or too little of dispersant may also be the reason. It needs to be verified that the cement is of right class. Also, if some cementitious extender is used, its reactivity also needs to be checked. Trying with adding extra retarder or optimizing the dispersant can help in this situation. It must also be considered that most of the industrially available dispersants have the retarding effects and retarders have dispersing effects. So, a balance needs to be established.

    Compatibility Issues (with the mud)

    Cements is hardly compatible with mud. However, the rheology check with mixtures of different compositions of mud/cement may give a quantitative perspective to the compatibility. The only way, in my opinion, to fight with the compatibility issues is to introduce the spacer with correct rheological hierarchy and wettability (in case of OBM/SBM).

    Static Gel Strength too Low (45 min)

    SGS is a parameter which works in conjunction with the fluid loss since it is related to the slurry gas-tight properties. Roughly, if the fluid loss is too much, faster gel strength development is required and vice versa. Gel strength modifiers can be used. However, they may lead to gelling of the cement slurry. So, a balance must be maintained between these and the other additives used in the slurry. Adding fine cementitious additives may also help in developing early gel strength.

    Compressive strength Development (too slow) or Max. value (too low)

    Compressive strength development is subjected to the concentrations of the additives. Too much retarder or a fluid loss additive with secondary effect as compressive strength suppressant may also lead to poor compressive strength development. A balance must be maintained. Sometimes, cementitious extenders having properties of compressive strength enhancers can also be used. Such additives help with early compressive strength development. Also, using a blend of fine and normal cement may also help with early compressive strength development. This also helps with the SGS. However, if gelling occurs, a balance between retarder and dispersant is needed. Optimization is the key.

    Hope this helps.

    Thanks,

    Kedar Sapte

    Reply
    • Lenin Diaz says

      April 14, 2017 at 12:13 pm

      Hi Kedar,
      Thanks a lot for this excellent contribution to this discussion.
      You have tackled each problem with clarity and technical knowledge, however taking your lead; I would like just to add a couple of things to enrich the conversation further.
      1. Firstly, in slurry gelation, the solutions can vary depending on when and how is the problem occurring:
      a) Right after mixing the slurry at surface, when left in static condition or false setting (different from thixotropic = fluidity not recovered after re-mixing).
      b) When taking rheology at BHCT
      c) When taking the Thickening time test, the gel appears as a plateau between (20 to 60 BC) that is maintained for sometime until it finally increases further
      d) Again during the thickening time test, the gel increases to a value of 20 to 70 BC and then decreases to relatively lower value until it finally increases again beyond the 70 BC mark
      All problems may be caused by a lower quality cement, however the second and fourth can be as well caused by other components such as the mix water or interaction between additives.
      Some solutions may include: (1) changing the cement source or batch, (2, 4) changing the source of mix water, (2, 4) increase the dispersant concentration, (2,3) using sodium silicate in low concentrations, (2, 4) changing the retarder type.
      2. Secondly, compatibility issues with mud vary and can affect rheology, thickening time and compressive strength development. As you mentioned, this is mainly a contamination problem which can be solved by “proper” fluid placement, however in some cases, like liner jobs (mostly deeper than 3000m) contamination could be unavoidable, in those cases and in the present of OBM, the use of a surfactant in the slurry may help in mitigating the effect.

      Thanks for your contribution and the opportunity to expand on the topic

      L. Diaz

      Reply
      • Kedar Sapte says

        April 16, 2017 at 5:13 am

        Thank you, Lenin for very nice information regarding gelation problem and spacer design.

        I would like to add one more point to the gelation (not sure if this had been covered in your answer). The slurry sometimes gel during HPHT conditioning/TT test and the Bc does not rise at all from that point on or occassionally, drops marginally depending on the slurry design water requirement. Simultaneously, sinusoidal slurry/oil temperature response is observed. This is the phenomena which is observed mainly in case of plugging of gelled up cement slurry around paddle shaft to form a thick lump while the rest of the thin slurry left around it. My past experience has shown that this occurs mainly because of the presence of too many fines in the cement (poor quality of cement grind) or cement chemistry is not as per API norms. Apart from changing the cement itself, this can be tackled by increasing/decreasing the dispersant and/or increasing retarder (this is a trial and error process and usually requires best judgement).

        Regards,

        Kedar Sapte

        Reply
        • Lenin Diaz says

          April 17, 2017 at 7:41 am

          Hi Kedar, beautiful addition indeed. I have seen similar problem before and I remember it took a while to solve it, but it wasn’t clear what actually did the trick. The only thing that was maintained was the cement, everthing else was changed. Now, Your conclusion about fines in the cement makes totally sense.
          Cheers
          L. Diaz

          Reply
  4. Jeff Long says

    April 20, 2017 at 11:39 am

    Lenin,

    Many times, as your flow chart suggests, the solution to whatever problem a slurry may have is a simple chemical addition. But, each addition may of course have an effect on the other properties as well, sometimes this is good, and we call it a multi-functional additive. Other times we need to add more of something else to counter act what is happening.

    So in contrast the solution to issues may be to reduce the quantity of an additive, including water or cement.

    Rheology to high:
    Will the density requirements be met with a lighter weight? Sometimes a 10th or two on density can be the difference. Same for rheology to low. Can the density be increased a little?

    Gellation is a broad term, but can often be treated in the same way. Compressive strength, Static gel, etc.

    My point is that we usually get locked into a density, even when density does not really matter. It is usually the most versatile property of a cement, yet we never vary. This is typically governed by tradition, no one wants to tell their customer that all their cementing objectives can be met with a 15.6 ppg (G) slurry.

    Manufacturing of API cement is not exact, that is why we have so many lab tests, the cement properties vary within the API acceptable range. But, if we accept this and have a customer that understands this, then we can save them a lot of money.

    Reply
    • Lenin Diaz says

      April 20, 2017 at 10:22 pm

      Happy to see such a good contribution Mr. Jeff. Thanks for that. I particularly like the reference to the density of the slurry, as cement itself (increase the density slightly) could be the solution to many problems.

      Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Primary Sidebar

Trango DEPM is a team of Oil&Gas professionals with broad experience in the O&G industry. Working on onshore and offshore projects around the world, including most vivid and challenging areas as Saudi Arabia, US Marcellus shale and North Sea, but also small on small projects, requiring individual approach, we are well equipped to help you plan, budget, implement and execute your drilling project successfully. We also cooperate with number of other professionals with experience in such areas as drilling, geology, geophysics, procurement or logistics. This allows us to fully run your project or just support you in desired areas of expertise, depends on you needs.

How I survived the 2016 Downturn and the current difficult times?

Find the content you need

Archives

24 Page Free Primary Cementing Guide

Click this image to take a look. It is comprehensive and easy to follow too!

In 2016, I launched Better Cementing for All. Now, I want to keep it alive.

For more than 26 years, I have worked in oil well cementing, offering my services to some of the largest oil corporations in the world and committing myself to excellence. I have mastered my role, and in doing so, I have accrued a skill set that is extremely valuable to my fellow professionals. Eager to do whatever I can to help them, I have owned and operated Better Cementing for All since 2016.
Let me tell you what Better Cementing for All does and what it means. A resource for all oil industry professionals and for cementers both established and prospective, this is a non-profit resource that I established in order to do nothing but serve and make an impact on people who are looking to build careers for themselves in cementing.
From primary cementing to remedial cementing to plug cementing to post-job results, I do it all, and I am comfortable answering in-depth questions about each and every one of these topics. I also offer tools and tips for jobseekers, general self-development advice, and guidance for equipment choices. TO put it simply, this is the go-to spot for anyone who wants to know anything about oil well cementing.
The problem, however, is that covid-19 has made the structure of the website seem untenable. I am trying to juggle the work that I do and my non-profit initiatives and finding it all unhealthy and unsustainable. I want to keep Better Cementing for All up and running, but to do that, I need your help.


My NEW introductory VIDEO

Recent Posts

Max out cement coverage

If we consider, the main variables to ensure proper mud in hole replacement with cement: stand-off, … [Read More...] about Max out cement coverage

Cementing Flowchart

In recent weeks, I received some reader requests to include cement job processes or procedures as … [Read More...] about Cementing Flowchart

Cementing. Challenges across permeable zones

This article will provide you with some actionable suggestions for cementing across permeable zones. … [Read More...] about Cementing. Challenges across permeable zones

Forensic Cementing

Forensic is a term usually associated with crimes. Criminal forensics is the use of science to … [Read More...] about Forensic Cementing

Cement Slurry design Basics

First, here is a handy table to simplify the process of cement slurry design: Additive … [Read More...] about Cement Slurry design Basics

well cementing pre-job cement challenge question

Remedial Cementing with Coiled Tubing (animation)

Far from being an animation expert, in my training courses, I always wanted to show my students a … [Read More...] about Remedial Cementing with Coiled Tubing (animation)

Need urgent help?

WhatsApp me at this number: +34 657 07 01 78

Footer

Recent activity

Visit our latest posts and help others by adding a comment.

Make your contribution and help keep Better Cementing for All alive!

Now more than ever, we are facing a loss of expertise in our industry, and Better Cementing for All is a unifying force, featuring interactions among industry professionals, knowledge sharing through posts, and other valuable pieces of content that we need to preserve.

Recent Comments

  • Lenin Diaz on All you need to know about Bentonite in Cement Slurries
  • Lenin Diaz on All you need to know about Bentonite in Cement Slurries
  • Lenin Diaz on Balanced-plug method. Basic calculations
  • Lenin Diaz on Max out cement coverage
  • Lenin Diaz on Balanced-plug method. Basic calculations
  • Mohamed on All you need to know about Bentonite in Cement Slurries
  • tom on Balanced-plug method. Basic calculations

Recent Posts

  • Max out cement coverage
  • Cementing Flowchart
  • Cementing. Challenges across permeable zones
  • Forensic Cementing
  • Cement Slurry design Basics
  • Remedial Cementing with Coiled Tubing (animation)
  • Webinar series (III). P&A (Spanish)
  • Webinar series (II). Quality Assurance in Cementing Operations (Spanish)
  • Webinar series (I). Log interpretation (Spanish)

Submit your email

&middot Better Well Cementing For All is owned by L. Diaz © 2022 &middot TOS & Privacy Policy &middot Web Design &middot