Abstract

Cement must be designed in a way to ensure acceptable properties such as mix ability, stability, rheology, fluid loss, and adequate thickening time. Different chemicals are used when designing cement slurries. These chemicals are used as retarders, fluid loss additives, dispersants, gas migration additives and expansion additives.

Typical examples of compounds used as retarders include: calcium lignosulfonate, sodium lignosulfonate, sodium tetra borate decahydrate (borax), starch derivatives, hydroxyethyl cellulose and weak organic acids. Examples of dispersants are ferrous lignosulfonate, acetone, and polyxythylene sulfonate. Many additives for fluid loss are water soluble polymers such as Vinyl sulfonate based on the 2-acrylamido-2-methyl-propane sulfonic acid. To the best of the author's knowledge, there is no study that compares the performance of different chemicals in cement designs.

The objective of this paper is to detail some of the cement chemistry and to go over the chemicals used in cementing oil and gas wells and their mechanisms of actions.

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