Foamed Cement – A Cement With Many Applications

ABSTRACT Foamed cement formulations have been developed which show promise for application: –as a cheap, economical and effective light-weight cement for application in formations with a low fracture gradient. Use of normal cements in these would cause the breakdown pressure in these weak formations to be exceeded, resulting in incomplete cement columns and inadequately supported casings. The density of the foamed cement may be easily adjusted in order to minimise cement losses while foamed-cement strength is being maximised.–as a means for curing lost circulation in areas where cavernous vugs cannot be plugged by conventional lost-circulation materials. Plugging by conventional cement also fails, since it flows to the bottom of the vug owing to its greater density. The use of a (thixotropic) foamed cement of density matched with that of the fluid in the vug will ensure that this gravity segregation no longer occurs.–as an expansive cement which will ensure good zonal isolation in zones where gas channelling behind the casing and pressurised casing annuli are frequently encountered. The expansive nature of foamed cement - owing to the gas contained in the cement - ensures that loss of hydrostatic head exerted by the cement column can be (partially) compensated for by expansion of the cement. Small-scale and large-scale laboratory tests showed that stable cements could be mixed and pumped. This was confirmed during a subsequent field test. This field trial was carried out using standard oilfield equipment without requiring the presence of specialists.