Page 159 - Geothermal Energy Systems Exploration, Development, and Utilization

3.4 Casing and Cementation 135

Top plug

Rupture disk

Bottom plug

High-strength
non-rotating
plate

Sure-Seal 3
float collar

Figure 3.16 Two-plug system. (Courtesy of Weatherford, 2008. Cementing Products.)

Care also has to be taken not to fracture the rock when pumping (high viscous)
cement slurries through narrow annuli, because the circulation pressure in the
annulus is acting on the bottom together with the ‘‘hydrostatic head’’ of the mud
and slurry column.
In general, it is recommended to calculate the ECD by a computer simulation
of critical cement jobs, taking into account rheology of the slurries and planned
pump rates.