Low density cement slurry and its use

摘要

A 9 to 12 ppg (1.08 to 1.4 kg/liter) cement slurry for use in oil well type completions which comprises hydraulic cement about 10 to about 30 weight percent hollow glass microspheres based on the weight of the cement and sufficient water to form a pumpable slurry with an API free water content of no more than about 2 volume percent. This slurry is preferably mixed with an amount of water required to produce a slurry with the hydraulic cement having at least an API minimum water content and an API free water content of no more than about 2 volume percent and an additional amount of water equal to about 1.3 to about 1.8 weight percent water based on the weight of the hydraulic cement for each weight percent of the microspheres. The microspheres have true particle densities of at least 0.2 gm/cm3, hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.