Properties of Well Cement
Well cementing involves pumping a sequence of fluids into the well. Often these fluids, such as spacers and cement slurries, have non-Newtonian yield-stress rheology. After the cement slurry has been placed in the annulus, it hardens into a low-permeabili
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Properties of Well Cement
Abstract Well cementing involves pumping a sequence of fluids into the well. Often these fluids, such as spacers and cement slurries, have non-Newtonian yield-stress rheology. After the cement slurry has been placed in the annulus, it hardens into a low-permeability annular seal. The complexity of these processes and the multitude of materials involved (drilling fluid, spacer, chemical wash, cement, casing, rocks) call for a sufficiently detailed material characterization in order to design and optimize cement jobs. A review of properties describing cements and other materials used in primary cementing is presented in this chapter. Rheological properties of washes, spacers, and cement slurries that control their flow down the well and up the annulus are discussed. Basics of non-Newtonian fluid rheology required to understand the subsequent chapters are laid out. Transition properties of cement slurry related to its solidification are reviewed. Mechanical, interfacial, hydraulic, and thermal properties of hardened cement that control e.g. response of cement to thermal stresses, vibrations, etc. are introduced, along with laboratory techniques used for their measurement (Brazilian test, uniaxial test, triaxial test, push-out test). Keywords Cement Measurement
Properties Rheology Yield stress Interface Strength
During a cementing job, cement undergoes a transformation from a liquid slurry being pumped down the wellbore to a solid material filling up the annular space between the casing and the borehole. While in the slurry state, the cement is characterized by rheological properties such as yield stress and plastic viscosity. These properties control the slurry flow and determine how cement displaces other fluids as it is placed behind the casing. The transition of cement from the liquid to the solid state is characterized by various properties e.g. volumetric change, rate of strength build-up or how easily formation fluids can enter the not-yet-solid cement. When hardened, cement is characterized by properties that determine how stable and permeable it is, how well it binds to the casing and the rock or how prone it is to fracturing. All of these properties need to be controlled in order to obtain a robust © The Author(s) 2016 A. Lavrov and M. Torsæter, Physics and Mechanics of Primary Well Cementing, SpringerBriefs in Petroleum Geoscience & Engineering, DOI 10.1007/978-3-319-43165-9_2
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2 Properties of Well Cement
low-permeability cement sheath in the well. Therefore, we start our journey into the world of well cementing by exploring some important cement properties.
2.1
Properties of the Cement Slurry
When cement is mixed on the surface or platform and is pumped down the well, it is in the liquid state. The flow of cement slurry and the fluid displacement in the well are largely affected by the rheological properties of the fluids and by their densities. From rheological viewpoint, spacers and cement slurries are non-Newtonian fluids. They have a yield stress, sY (Pa
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