Introduction

In well cementing, Portland cement systems are designed for temperatures ranges from below freezing in permafrost zones to 662°F (350°C) in thermal recovery and geothermal wells. They also encounter pressures ranging from ambient to 30,000 psi (200 MPa) in deep wells. Accommodation of such variations in conditions was only possible through the development of cement additives. According to American Petroleum Institute Recommended Practice 10B, additives are materials added to cement slurry to modify or enhance desired property Anon. Cement additives selected for cementing operations are an integral part of sound well design, construction and well integrity. Additives are available to enhance the properties of oil well slurries and achieve successful placement between the casing and the geological formation, rapid compressive strength development and adequate zonal isolation during the lifetime of the well. According to Cowan and Eoff, additives are commonly added to cement formulations to; disperse cement particles, modify the setting time under temperature and pressure conditions in the well, control filtration losses of the liquid from the cement slurry during and after placement, compensate for shrinkage of the cement as it sets and hardens, improve interfacial bonding between cement and casing, and control influx and migration of formation fluids into the cement column during setting. There are different types of cement additives that have been developed to allow the use of Portland cement in many different oil and gas well applications Anon. Each type has different types of additives that have been developed to perform almost the same function during cement slurry design. However, there are some additives under each major type that are commonly used in cement slurry design for oil and gas well cementing operations. This paper reviews the broad classification of oil well additives giving emphasis to the commonly used ones in oil and gas well cementing operations.

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– Eric Broni-Bediako, Ogbonna F. Joel and Grace Ofori-Sarpong

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