The filtration process during cementing where the aqueous phase escapes into the formation leaving behind cement particles is called what?

• A. Bleed-off
• B. Filtration
• C. Hydration
• D. Fluid Loss

Answer: (D)

When cement slurry is pumped into a well, water tends to move into the surrounding rock pores. This movement of liquid out of the slurry into the formation is called fluid loss. As the filtrate leaves, solids stay behind and a filter cake forms on the borehole wall, which helps regulate further loss. In cementing practice, fluid loss specifically describes the amount of aqueous phase that escapes into the formation during placement. The other terms don’t fit this scenario as closely: filtration is the general process of liquid moving through a porous medium, but the field uses fluid loss to denote the practical, measured loss during cementing; bleed-off refers to water separating from the cement after it has set; and hydration is the chemical reaction cement undergoes with water to form hydrates.