Foamed Cement: A Second Generation

Abstract

ABSTRACT Advanced technology in design and implementation of stable foamed cement systems now offers new solutions to critical oil-field cementing problems well beyond the original utility of lightweight slurries in reducing hydrostatic pressure across fracture-sensitive zones. Implications of new high-performance foamed cement capabilities are discussed for specialized applications such as thermal recovery, deep cementing in a narrow annular gap, lost-circulation control and stimulation across fractured or washed-out zones, as well as other unique advantages in primary cementing. Specialized foamed cement studies reveal improved prevention of strength and permeability retrogression and enhanced thermal isolation for steamflood applications, all at significantly reduced fracture stress as compared to conventional extended systems. Because of their unique rheology, high-performance foam slurries can be designed to exhibit moderate thixotropy but maintain excellent fluidity at extremely low shear. Cement foams further aid zonal isolation due to improved shear bonding and enhanced pipe/cement/formation contact as a result of the expansive nature of the slurry during setting. A number of successful jobs are documented in which lightweight nitrified systems placed across weak and washed-out zones have been successfully perforated and fractured. Several new potential applications for moderate to high-density, stable, nitrified slurries are also discussed based on their unique performance.