• 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.

Cementing. Challenges across permeable zones

February 3, 2021 By Lenin Diaz Leave a Comment

Cementing. Challenges across permeable zones

This article will provide you with some actionable suggestions for cementing across permeable zones. In previous posts, I have already talked about the effect of formation permeability on the apparent cement presence behind casing, as seen on cement logs. (See: Excellent cement job, but with terrible results … how is this possible?)

Keep in mind that the dominant factor is the loss of filtrate to the formation, as presented in A talk about API Fluid Loss and Mud Displacement, the ‘mystery’ factor in gas and fluids migration. There are two cementing defects typically identified, as described below:

1) Delayed compressive strength development.

This defect is defined as the development of insufficient compressive strength in the cement at the time of running the cement evaluation log, usually 3 to 8 days after the end of the cementing operation. (Much longer than the curing period required to achieve proper compressive strength as per a 24 hr.-UCA reference, for example).

Depending on the length of the section (as applicable to cement slurry volume) and the extension of the permeable zone, I have found this effect to be mainly related to mud properties (fluid loss and viscosity). This leads to lower displacement efficiency before cementing (pre-job circulation – see A talk about API Fluid Loss) and higher while cementing by the cement slurry itself across the permeable zone.

Ultimately, this leads to cement slurry contaminated with previously immovable mud (composed of gelled mud and remnants of thick-porous filter cake) and delayed compressive strength. In a previous experience, the comparison between cement logs days apart helped to highlight this effect (before perforating). However, this is not enough for regulators and company policies to be modified, with the promise of improved zonal isolation in a time when early cement logs appear unacceptable. NOTE: This doesn`t account for the possible contribution of formation movement, e.g., creeping shales.

Cementing log graph for illustrating cementing across permeable zones
Cement evaluation log after one week of curing time still showing “green cement” (blue line). The red line shows the cement evaluation log done after three weeks. This is the kind of response expected to be seen in the initial log if compressive strength has occurred as reported in the laboratory test.

2. High amplitude or “bad cement” across the best reservoir section.

This defect can be defined as very clear deterioration on the cement log, showing almost no cement, across the section of the reservoir with higher permeability. In the previous graph, the red line shows this defect at the bottom of the interval.

Recommended actions for cementing across permeable zones

For cement density in the conventional range, the balance between slurry density and fluid loss control. As cement logs are affected by the compressive strength of the slurry, it is important to implement actions specifically intended to maximize not only compressive strength but also its earlier development. For example, increasing the cement slurry density a small fraction (between safety limits).

This will have a positive effect to mitigate contamination and improved compressive strength. Also, it can reduce the need for high fluid loss control, (most fluid loss control additives have a reducing-negative effect on compressive strength), relying more on dispersion to control the loss of filtrate taking advantage of the lower porosity of the slurry. Keep in mind this recommendation is offered in the context of formation interaction after placement across a permeable zone.

For lower density applications, target low porosity slurry systems.

Proper selection of target thickening time. Understand and manage safety factors that increase the thickening time to prevent their escalation effect creating a fictional or inexistent more severe downhole “well condition”.

For example, the:

  • Definition of the BHST itself
  • Implied safety factor in the method of BHCT estimation
  • Calculation of operational time in liners
  • Need and introduction of static periods in TT test
  • Long cement columns
  • “Round-up” retarder concentration in the field
  • Safety factor itself.

Use temperature simulation to assess the wellbore heating schedule after placement to program the UCA and prevent overestimating the 24 hr.-CS UCA value (to derive acoustic impedance reference for “good cement” in logs).

Run a contaminated UCA test, with contamination percentage as per computer simulation.

Use of retarders that offer the lowest gap between thickening time and time to develop 50 psi CS.

Use of fibres in the cement slurry volume, to help minimize the loss of filtrate by reducing the permeability at the cement-formation interface.

Maximize cement coverage using software simulation, from pre-job circulation (displace mud by mud, targeting the risk of immovable mud), mud displacement, channelling prevention to casing stand-off.

Consider casing rotation to ensure cement presence 360 degrees across the interval of interest. Friction exerted on the formation face by pipe rotation has also shown straightening or pore-plugging capabilities lowering the near-wellbore formation permeability.

Show your support here

Really looking forward to reading your comments,

Cheers,

L. Diaz

Related posts:

  1. Workover Cementing Techniques 2: Squeeze Cementing
  2. Misconceptions About Cementing
  3. Cement Slurry Laboratory Testing
  4. Cement Bond Log and Variable Density Results

Filed Under: Primary Cementing Tagged With: API fluid loss, best practices, fluid loss, permeable

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

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 Your Cement Coverage

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

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)

Though I am far from being an animation expert, during my training courses I have always wanted to … [Read More...] about Remedial Cementing with Coiled Tubing (animation)

Illustration: cement substitutes to provide zonal isolation

Plug and Abandonment Webinar (Español)

I am very happy to present here a webinar on plug and abandonment on well cementing for my … [Read More...] about Plug and Abandonment Webinar (Español)

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

  • Merit on Cementing Equipment from Serva SJS Limited
  • Lenin Diaz on Cementing Equipment from Serva SJS Limited
  • Lenin Diaz on All you need to know about Bentonite in Cement Slurries
  • Lenin Diaz on Cementing Equipment from Serva SJS Limited
  • Lenin Diaz on Cementing Equipment from Serva SJS Limited
  • Lenin Diaz on Suicide Squeeze Cementing: risky but valid
  • Samuel Bekele Bedjiga on All you need to know about Bentonite in Cement Slurries

Recent Posts

  • Max Out Your Cement Coverage
  • Cementing Flowchart
  • Cementing. Challenges across permeable zones
  • Forensic Cementing
  • Cement Slurry design Basics
  • Remedial Cementing with Coiled Tubing (animation)
  • Plug and Abandonment Webinar (Español)
  • 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 © 2023 &middot TOS & Privacy Policy &middot Web Design &middot