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Basic Knowledge
6.2 Cenosphere
  • Detailed description

The cenosphere is a kind of glass beads screening out from fly ash. When the fine grinding fly ash is burning in a power plant, some of the ash will melt; the melt ash will shrink into spherical in the action of the surface tension. It becomes the hollow sphere under the action of cold air when it is ejected from the nasty. Put the fly ash into a pool, the particles with low density floating in the water, and collecting and drying the floating particle can get the cenosphere. When cementing in the easy leak strata and geothermal well section, the cenosphere ect lighting material is needed to reduce the cement density and solve the well leakage caused by high cement slurry density.
The main chemical composition of the cenosphere is silica and aluminium oxide. It has a variety of functions such as the fine grain, hollow, light, high-strength, wearable high-temperature, resistance to abrasion, insulation and inflaming etc. The main chemical composition is showed as follows:

Ingredient

SiO2

Al2O3

Fe2O3

CaO

MgO

K2O

Na2O

Content (%)

56~62

33~38

2~4

0.2~0.4

0.8~1.2

0.5~1.1

0.3~0.9

As the oil well cement admixture, the cenosphere should satisfied the following technical indexes:
Density: quality cenosphere’s apparent density should below 0.7g/cm3, and the mass difference should greater than 0.8/cm3.
Particle size: the mesh of cenosphere used in cementing generally is from 40 to 60 meshes.
Atmospheric damage rate: generally it should lower than 15%.
Damage rate under pressure: as the oil well cementing admixture, the damage rate under pressure should lower than 35%, and the worst should not greater than 60%.