‘Garbage in, Garbage out’
… is an expression unfortunately applicable to so many human activities in today’s world. Social media is a clear example of this, but it is also a term sadly familiar to those who have experience with cementing software and computer simulations. Why?
… Not sure exactly, but a lack of skills or experience by the user, insufficient or incorrect input of data are probably the leading causes.
In cementing, if we go back to basics, computer simulation via cementing software (e.g. by Schlumberger) is a powerful tool. It is typically used during the job design phase. It allows the proper selection of fluid properties, centralizer placement and the prevention of losses or influxes to maximize cement coverage. However, like any computer-based activity, it requires adequate knowledge, skills and understanding of the physics behind it.
Cementing software is fairly easy to use
Any cementing engineer with at least three years experience is aware of the basics of cement placement computer simulation. However, this is the moment where the problems start to appear in some cases. That exact moment when the young engineer loses the connection between the cementing software world and the real world. What this means is that the most crucial aspect of any simulation, the model, loses priority over the output…. So, indeed ‘Garbage in Garbage out’ … and the simulation becomes obsolete from the very beginning.
The model is nothing but how the real world is described to the computer simulation software to do its job. If the model is simplistic or full of assumptions, then the output of the simulation is just one out of many possibilities.
Unfortunately, for some young engineers (and others not so young, I must say, because skills are not necessarily linked to age or years of experience), as long as there is an output, the job is done. It is put on paper, signed and sent to the field for deployment. Then the cycle is repeated for the next well and the future wells after, even if the job doesn’t achieve the objectives. The same process is repeated over and over until a job finally fails catastrophically. Then nobody knows why which opens the door to higher costs and loss of time for the operator. This higher cost takes many forms, remedial jobs, NPT, higher cementing costs, etc.
In this cycle of insanity (remember the definition of insanity: “doing the same thing over and over again and expecting different results” by Albert Einstein) it is missing what makes us Engineers in the first place: The Analysis.
Design – Execution – Evaluation
The analysis is what makes the difference on the next job; what produces learning, develops knowledge and takes us closer to the best practice. Coming from a company who mastered the DEE cycle, (Design – Execution – Evaluation), I value the importance of job analysis and evaluation above everything else, and it holds the real value and power of computer simulation, in the form of a post-job analysis.
Post-job analysis allows us to understand why we have failed or succeeded in a cementing operation. The core of any post-job analysis, also called pressure analysis, is the computer simulation, which allows us to compare the design on paper with the actual results to answer questions, like:
- Why if the design (simulation) predicted a perfect cement coverage, the cement log is showing no cement; or
- If the design predicted poor cement coverage instead, why is the cement log is showing a perfect cement bond?
Nothing is by chance
Everything that happens has an explanation and in consequence a learning opportunity. We might not identify this explanation entirely after just one job, but after several, however, we can see improvement every time if we do our job right.
Computer simulation on cementing software becomes a critical and valuable tool to achieve the best performance and in the process. Every person in the team absorbs and owns this learning, which gives satisfaction and maximizes the team’s performance. This way cementing is more than what is on books, it is a process that they understand how it works, and more specifically how it works for their wells.
This is the real power of computer simulation, the power to create collective learning and maximize performance.
Obviously, this process needs a leader or change agent taking care of the well-cementing speciality; here the most natural individual is the cementing engineer with the service provider. However, very often He or She is a resource shared by several contracts with barely enough time to put together a design. The next logical alternative for a leader is the Cementing Specialist if there is one; if not the Drilling Engineer can also perform this task depending on the workload.
Computer simulation, or more specifically post-job analysis, is the most critical aspect of well-cementing because anybody knows what is in books and most certainly anybody knows how to calculate a cement volume. Only good cementing engineers can create a culture and develop a successful practice taking advantage of the real power behind Computer Simulations.
I hope you find this short article interesting, and if you have any comments or questions, please let me know.
Lucio Campaña says
Excelent post, The developement of proper practices for simulations, the knowledge of the physics, chemistry of the systems as a whole, and as you said the post job analysis and the hypothesis these can prove or discard are of tremendous importance
Lenin Diaz says
Thanks Mr. Lucio for your very rightful remark. Tell me how are things with you these days?
Victor Bustamante says
Long time ago, the computer software simulators let to correlate: Cement placement vs well bonding cementing logs; expected pressure & flow chart vs real pressure & flow chart; and now it is possible to compare the measure the rheologies of lab slurry vs field slurry.
At conclusion, it is possible to fail a cementing job using a software simulator (due different reasons); but it is impossible to success a cementing job without a software simulator. Indeed, sofware simulator with the electric cement logs are the unique tools to identify in which stage the cementing job failed: design, execution or post execution (post placement).
Lenin Diaz says
Thanks for your comment Victor. It is a good contribution to the discussion and helps conceptualize the importance of computer simulations in our job. Hope to see you back soon here or other post in my site.
Mike Cowan says
A valuable discussion. The complexity of the fluid-fluid displacement process is grossly under-appreciated by most of the industry. Each of the models has at least one significant deficiency (something missing or how part of the problem is handled by the model). It would be beneficial to the the industry to build one standard, accurate model from all that is currently known. Multiple-simulations are recommended to identify ‘sensitivities’ to any of the variables to define the optimum ‘operating envelope’ of the process that produces the desire results. Finally, I appreciate emphasis on post-job analysis…very valuable part of learning and optimizing. I appreciate the chance to post on your site. Happy you are doing this work!
Lenin Diaz says
Thanks Mike for your comment and words. Your reference to deficiencies in current industry available simulators is very correct, however, as you said, once the model is built multiple simulations provide a better understanding of what variables would have more impact on the results.
Interesting article. As a Drilling Engineer worked on challenging environments, I see the value of having a cementing specialist in the team to look after design, lab tests, cement design and simulations and more importantly leading all post job quality issues. Everyone knows that the Drilling Engineer is focused on get things ready for next hole section and may miss following up with service providers about the issues during the job and after the job. ( logs, drill out and pressure integrity)
Such position can save huge amount of money for the operators.
Lenin Diaz says
Thanks for your comment Gaz.
On this one, I fully agree