Jean-Francois Baret

3 Cement Additives and Mechanisms of Action

Publisher Summary This chapter summarizes the major categories of well cement additives, their principal benefits, chemical compositions, and mechanisms of actions. The physical and chemical phenomena with which the additives contend are discussed in the chapter. Portland cement systems are routinely designed for temperatures ranging from below freezing in permafrost zones to 700°F (350°C) in thermal recovery and geothermal wells. Well cements encounter the pressure range from near ambient in shallow wells to more than 30,000 psi (200 MPa) in deep wells. In addition to severe temperatures and pressures, well cements are often designed to contend with weak or porous formations, corrosive fluids, and overpressured formation fluids. Over 100 additives for well cements are available, many of which can be supplied in solid or liquid forms. Eight categories of additives are generally recognized, which are, accelerators, retarders, extenders, weighing agents, dispersants, fluid-loss control agents, lost circulation controlling agents, and speciality additives.