Cement free slurry water

Small-particle-size cement has found a number of uses in production and injection well casing repair jobs [440]. Oil-based cement is particularly useful for water shutoff jobs, because the hydrocarbon slurry sets only in the presence of water, so the oil-producing sections of a reservoir remain relatively damage free after water shutoff. The selective water shutoff with oil-based cement also has been used with polymers crosslinked by metal crosslinkers [442,1178]. 

The maximum amount of water for any class of cement is usually defined as the ratio that results in the cement particles remaining in suspension until the initial set of the slurry has taken place. If more than the maximum amount of water is used, then the cement particles will settle in such a manner that there will be pockets of free water within the set cement column. 

Specific weight is one of the most important properties of a cement slurry. The specific weight of a certain dry cement regulates the minimum or maximum amount of water allowed to be added. The minimum amount of water, from the aspect of density, is greater than the stoichiometric quantity necessary for proper setting. If more than the maximum amount of water is used, pockets of free water will be formed in the set cement column. Typical amounts of water range from 38% to 46% by weight in the final mixture. 

A dispersing agent for a cement slurry is the magnesium salt from the condensation of napthalenosulfonic acid and formaldehyde [815,816]. The additive eliminates free water, even at low temperatures and with those cements most susceptible to this phenomenon. 

Highly fluid cement slurries with good water retention characteristics are used to grout the space between the formation and the metal pipe in the construction of oil wells. The grout must be highly fluid to prevent excessive friction during placement, must not lose water to the formation, and must provide ample low-shear viscosity to prevent creating free water and... 

Mechanically agitated thickeners are usually large, typically 10 to 100 m (30 to 300 ft) in diameter and 2,5 to 3.5 m (8 to 12 ft) deep. In a large thickener the rakes may revolve once every 30 min. These thickeners are especially valuable when large volumes of dilute slurry must be thickened, as in cement manufacture or the production of magnesium from seawater. They are also used extensively in sewage treatment and in water purification. The feed pulp is admitted at the centerline of the unit at a depth of 1 m or so below the surface of the liquid. Above the feed level is a clarification zone in which the liquid is almost free of solids. Below the feed level is a zone of hindered settling and, near the bottom, a... 

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