Oil Well Cement Additives

Most oil well cement slurries will be added to some additives in order to modify cement properties so cement operation can be properly performed. In this article, it will cover some of important cement additives in general terms so that it will help you understand the basic function of each additive.

oilwell-cement-addtives

Accelerators

Accelerators are added to shorten the time for cement to properly set and it will reduce rig time while waiting on the cement (WOC). Accelerators are crucial in shallow depths where bottom temperature is low. In the deeper section, it may not require an accelerator, because the well is hot enough and the thickening time will be normal. The WOC time is generally based on the time required to obtain 500 psi compressive strength of the cement.

Chemical used as accelerators are as follows;

  • Calcium chloride 1.5 – 2.0 %
  • Sodium chloride 2.0 – 2.5%
  • Sea water

If the percentage of these additives is high, they will act as retarders instead of accelerators.

Retarders

Retarders have the opposite function as accelerators because they are used to prolong thickening time of cement in order to prevent premature setting of cement. Retarders are used in the deeper hole section where bottom hole pressure is high.

Chemical used as retarders are as follows;

  • Calcium lignospulphanate
  • Saturated salt solution

Light Weight Additives (extenders)

Lightweight additives are used to reduce slurry density. Some sections in the well may require a reduced cement weight because a formation fracture gradient is quite low. With normal cement density, it can cause cement losses and it will result in a bad cement job. Reducing the cement density will cause decreasing in compressive strength and increasing in thickening time.

Chemicals used as light weight additives are as follows;

  • Bentonite (2%-16%)
  • Pozzolan
  • Diatomaceous earth (10%-40%)

Heavy Weight Additives

Heavy weight additives are added in order to increase slurry density. Some overpressures zones must be cemented with a high density cement.

Chemicals used as heavy weight additives are as follows;

  • Barite
  • Hematite
  • Sand

Fluid Loss Additives

Fluid loss additives are added to prevent dehydration of cement; therefore, the cement will maintain proper water portion and the cement properties will not be destroyed. Squeeze cementing requires a low fluid loss because cement must be squeezed into intended zones before the filter cake builds up. Fluid loss for a primary cement job maybe as critical as a squeeze cement job.

Chemicals used as fluid loss additives are as follows;

  • Organic polymers 0.5 – 1.5%
  • Carboxymethyl hydroxyethyl cellulose 0.3% – 1.0%

Friction Reducing Additives

Friction reducing additives are used to improve the cement slurry flow properties. The additives will reduce the viscosity so that turbulence flow will happen with a low pumping pressure. With the help from friction reducing additive, the risk of fracturing formation from excessive pressure can be minimized.

Chemicals used as friction reducing additives are as follows;

  • Polymers 0.3 – 0.5lb/sx
  • Salt 1-6 lb./sx
  • Calcium lignosulphanate 0.5 -1.5 lb./sx

Referrences

Baker, R. (2001) A primer of oilwell drilling: A basic text of oil and gas drilling. 6th edn. Austin, TX: Petroleum Extension Service, Continuing & Extended Education, University of Texas at Austin.

Mitchell, R.F., Miska, S.Z. and Aadnoy, B.S. (2012) Fundamentals of drilling engineering. Richardson, TX: Society of Petroleum Engineers.

Bourgoyne, A.T. (1986) Applied drilling engineering. Richardson, TX: Society of Petroleum Engineers.

Please follow and like us:
0

Related Post

Cement Calculation Overview and Basic Terms that P... Cement slurry calculation (volume, density, yield) are quite simple and the basic behind is mass balance calculation. Cement calculation for common li...
Calculate Cement (Oil Well Cement) Volume Required Cement volume calculation is based on annular capacity multiplied by length of cement as per cement program. This topic will demonstrate you how to de...
Accumulator (Koomey) An accumulator or Koomey unit is a unit used to hydraulically operate Rams BOP, Annular BOP, HCR and some hydraulic equipment. There are several of hi...
Applied Drilling Engineering (Spe Textbook Series,... If you would like to learn about drilling engineering, this book, Applied Drilling Engineering - Spe Textbook Series, is my recommendation. The book c...

About DrillingFormulas.Com

Working in the oil field and loving to share knowledge.
Tagged , , , . Bookmark the permalink.

One Response to Oil Well Cement Additives

  1. behnam says:

    VERY GOOD this article. If the field were presented in this article like that was better. For example, the casing 9-5 / 8 ” substances added to cement

Leave a Reply

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