Oil well cements - Special Inorganic Cements - page 349

27.2
OTHER OIL WELL CEMENTS
API Class J cement is basically a combination of -dicalcium silicate and quartz
interground in an approximate proportion of 60:40 (belite-silica cement). This type of
cement is especially suitable for applications in deep oil wells and high-temperature
geothermal wells, owing to its very low reactivity. At temperatures below 100°C very
little hydration occurs, even after several hours of curing: an amorphous C-S-H phase and
calcium hydroxide are formed in the hydration of dicalcium silicate, whereas the quartz
that is present does not participate in the hydration reaction. At temperatures above 100°
C quartz becomes gradually involved in the hydration process, even though the reaction
still proceeds much more slowly than with Class G and Class H cements. Amorphous C-
S-H and crystalline tobermorite are formed as the main products of reaction, as well as
some xonotlite and gyrolite. If needed, the progress of the reaction can be slowed down
further by adding suitable retarders to the mix.
Calcium aluminate cement may be considered for low-temperature cementing,
especially in arctic conditions.
A calcium phosphate binder to be used as a lost circulation control material for
geothermal wells may be produced by combining high-alumina cement with sodium
phosphate and with borax serving as retarder. The high-alumina cement may be partially
replaced by ground granulated blast furnace slag (Allan and Kukacka, 1995).
A sodium metasilicate modified high-alumina cement may be used in geothermal wells
at temperatures up to 300°C (Sugama and Garciello, 1996). Sodium calcium silicate
hydrate and boehmite are formed as products of reaction in the hydrothermal reaction.
Portland cements extended with class F fly ash from coal burning power plants may be
used for filler applications (Reeves, 1991) and for lightweight cement slurries. The fly
ash content may reach up to 50 wt%.
Portland cement combined with granulated blast furnace slag may be used for general
applications.
Combinations of granulated blast furnace slag with quartz sand have been used for
high-temperature cementing (above 110°C).
REFERENCES
Allan, M.L., and Kukacka, L.E. (1995) Calcium phosphate cements for lost circulation
control in geothermal drilling. Geothermics 29, 269-289.
Bensted, J. (1985) Oil well cements: a general review. Chemistry in Industry (London) 4,
100-105.
Bensted, J. (1989) Oil well Cements. World Cement 20, 346-357.
Bensted, J. (1991) API class C rapid-hardening oil well cement. World Cement 23, 38-
41.
Bensted, J. (1992a) Oil well cement standards: an update. World Cement 23, 38-44.
Bensted, J. (1992b) Class G and H basic oil well cements. World Cement 23, 44-50.