1. Field of the Disclosure
The disclosure relates generally to apparatus and methods for cementing boreholes.
2. Description of the Related Art
Cementing is a technique employed during many phases of borehole operations. For example, a cement slurry may be employed to cement or secure various casing strings and/or liners in a well. In other cases, cementing may be used in remedial operations to repair casing and/or to achieve formation isolation. In still other cases, cementing may be employed to isolate selected zones in the borehole and to temporarily or permanently abandon a borehole. Several factors may affect the performance of the cement in the borehole (or “wellbore”), including, but not limited to, length of the cement column in the borehole, formation pore pressure, formation fracture gradient and cement slurry density. In some embodiments, the density of the cement or cement slurry may affect the structural integrity of the formation rock. For example, a cement slurry with a heavy density may impart increased pressure and force on the formation rock. The increased pressure can lead to breakdown of the formation, reducing borehole integrity. In addition, the cement slurry hardens or sets after being directed to a selected location in the borehole and may expand and/or contract over time. Expansion and contraction of the cement slurry after hydration or hardening can cause cracks to develop, thereby allowing fluids to leak from the formation.