Cenospheres
Cenospheres or Fillite® are hollow alumino silicate spheres. Cenospheres are a small fraction of fly ash produced by burning coal at thermal power stations.
In the Offshore environment Fillite® is used in oil well cements. Low density slurries can be achieved using cenospheres, slurries incorporating censopheres are of lower densities than those with conventional extenders.
Cenospheres are compatible with all types of cement and are advantageous due to their high compressive strength.
Cement slurries exhibit good thermal insulation (Fillite® has a K value of 0.09) thus making cement slurries based upon Fillite® ideal for geothermal applications.
Fillite® cenosphere's spherical nature gives a lubricating effect to the cement. This means that low water to cement ratios can be used and strength development is, as a result, much faster.
Fillite® also imparts good flow, this is an advantage in that it allows for slurries to be easily pumped over long distances.