CEMENTING HARDWARE
: Some or all of the following equipment is used during cementing operations
Guide shoes
A guide shoe is used to guide the casing through the hole, avoiding jamming the casing in
washed-out zones, or in deviated wells. It can be a simple guide or may contain a ball valve
or flapper valve, Figure below. When a guide shoe contains a valve element it is described as
a float shoe. A float shoe prevents cement from flowing back into the casing once the cement is
displaced behind the casing. Shoes have either inner parts made of aluminium or cement; both
being easily drillable, with the advantage that cement is more resistant to impact. Float shoes
have all the advantages of the guide shoes, plus the float valve to avoid back flow and provide
casing buoyancy. The main disadvantage of a float shoe is the extra time it takes to run casing
in hole (RIH); with casing running operations temporarily stopped to fill the casing from the
top. By using an orifice fill shoe (automatic fill-up shoe), RIH time can be reduced as the casing
.is filled up while running in hole
Centralisers
A centralizer is a mechanical device attached to the outside of casing. The primary purpose of
this equipment is to center the casing in the hole and provide a uniform flow passage with
relatively equal frictional pressure losses surrounding the casing. Another major function of
.centralizers in a deviated hole is to help prevent differential pipe sticking
Float Collars
A float collar is a one way valve placed at one or two joints above the shoe. The float collar
provides the same functions as a float shoe by preventing fluid back flow into the casing
mud backflow during running in hole and cement slurry backflow after cement displacement
The distance between the shoe and float collar is called Shoe Track. The float valve can either
be a ball type or a flapper, Figure below. Flapper type valves are normally used where a small
.hydrostatic pressure difference is expected, providing a better seal than a ball type valve
Cement Baskets
Cement baskets protect weak formations from excessivehydrostatic pressure exerted by the
weight of the cement column. They form a restriction against a downhole fluid motion by
reducing the flow area. They are normally installed on the casing string above weak
formations, but they are also used in stage cementing or in cementing the annulus from the
.surface