Inorganic additives used to shorten the thickening time of a cement slurry and accelerate the development of compressive strength. They are primarily used in low temperature applications.
Organic, acidic or synthetic material that prolongs the thickening time of a cement slurry. Retarders are used in higher temperature wellbore environments or when there is a need to have a longer thickening time due to a large volume or low pump rate of the slurry.
Fluid loss additives
Polymers or starches used to control the amount of filtrate that is allowed to leave the cement slurry when exposed to a differential pressure. This differential occurs when a formation is permeable and the ECD or EMW is greater than that of the pore pressure. Fluid loss additives are also used to control filtrate loss when cementing past water sensitive formations such as shale and salt formations.
Polymer- or clay-based materials used to increase the viscosity of the cement slurry. Used to maintain rheological hierarchy with neighboring fluids to promote effective fluid displacement and to combat the effects of thermal thinning.
Sulfonated polymers that lower the fluid’s viscosity and improve mixability. Dispersants allow mixing slurries heavier for applications such as kick-off plugs.
Materials with either a low specific gravity or ability to absorb a large amount of water during hydration or a chemical reaction. They are typically used to reduce the hydrostatic pressure or to aid in lowering the cost of a cement slurry.
Materials with a higher specific gravity than the base system used to increase the density of the slurry to allow for hydrostatic control of the wellbore during cementing operations.
Strength Retrogression Additives
Silica-based additives used to help sustain a set cements compressive strength in environments with temperatures in excess of 230 oF.
Decrease a slurry’s propensity to foam and entrain air.
Gas Migration Control
Additives that reduce gas migration through the cement column when static. Wellbores with high pore pressure or low hydrostatic pressure of the final cement column require these type of additives. They may be either polymer based or expansive.
Lost Circulation Additives
Particulate or fibrous additives that bridge off at loss-circulation zones to allow for successful cement placement.
Surfactants that improve entrainment of nitrogen in foam cement blends.