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Effect of Cellulose Nanocrystal Particles on Rheology, Transport and Mechanical Properties of Oil Well Cement Systems

  • Author / Creator
    Dousti, Mohammad Reza
  • The increase in oil consumption during the past few decades, coupled with oil/gas extraction from shale in the recent years has increased drilling and cementing demands. Well cementing operation is one of the most crucial and important steps in any well completion. However, since it takes place at the end of the drilling process (each segment), a satisfying and acceptable job is rarely done. In the cementing process, cement is used to fill in the annular space between the casing string and the ground formation within the drilled hole. The cementitious system placed in an oil well has exclusive functions to perform. These include restricting the movement of hydrocarbons and/or water in between the permeable zones, providing a suitable mechanical support for the casing string, protecting the casing from any sort of physical damage including corrosion, and supporting the well-bore walls in order to prevent the collapse of the formation. The prepared paste has to be satisfactorily pumpable and flowable. However, on the other hand, the viscosity and yield stress associated with the paste should be appropriately tailored in order to reduce the risk of lost circulation. Therefore, the rheological behavior of an oil well cement paste should be assessed carefully. Also, the fluid loss (filtration) rate of the prepared cement paste is of great importance since it directly impacts various characteristics of the hardened cement sheath. High filtration and fluid loss rate lead to a change in the water-to-cement ratio of the matrix, influencing not only the flowability of paste while still fresh but also the microstructure of the hardened cement paste. Furthermore, the hardened oil well cement sheath placed in a wellbore should demonstrate adequate mechanical properties. Therefore, while designing the slurry, the strength development rate along with the ultimate compressive and tensile strength of the hardened paste should be taken into consideration. Moreover, understanding and improving the transport properties of oil well cement paste is essential. The aggression of any type of destructive and detrimental agents through the hardened paste will eventually degrade the cementitious system. Thus, the permeability and pore structure of the hardened oil well cement paste placed in the annulus is extremely critical. This study was primarily associated with the material behavior of oil well cement paste in the presence of cellulose nanocrystals. The main goal of this research was to develop an oil well cement system and address the associated durability concerns mentioned above. Firstly, the workability and the rheological properties of CNC-dosed fresh oil well cement paste were assessed, followed by static filtration tests to evaluate fluid loss. It was found that adding CNC to oil well cement paste leads to shear thinning which manifests as lower slump for the cement based slurry. Also, based on the experimental results, the presence of CNC increased the time required to collect a given amount of filtrate. Furthermore, the effect of cellulose nanocrystal (CNC) particles on the dynamic mechanical properties of oil well cement paste was studied. Using oscillatory rheology, the linear viscoelastic range of CNC-dosed oil well cement paste was determined and the frequency sweep test was performed at the critical strain. According to the results obtained, the presence of CNC enhanced the complex viscosity, rigidity, hydration rate and solidification of oil well cement paste. Moreover, the effect of cellulose nanocrystal (CNC) particles on the pore structure and porosity of hardened oil well cement paste was investigated using the gas sorption technique. The strength development (compressive and tensile) of CNC-dosed oil well cement paste was also measured at different ages in order to recognize the impact of this nanomaterial on the mechanical properties of hardened oil well cement paste. Test results revealed that CNC particles reduced the porosity and surface area of hardened oil well cement paste and enhanced the mechanical properties. Finally, the mass flow rate of early aged hollow cylindrical specimens dosed with CNC was measured by using a pressurized permeability cell and the water permeability of the specimens was evaluated using Darcy’s law for laminar flow. The water permeability of oil well cement paste was reduced with the addition of cellulose nanocrystal (CNC) particles.

  • Subjects / Keywords
  • Graduation date
    Spring 2018
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/R3TB0Z949
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.