wellcemented

Well cemented is an adjective describing a borehole in which the annulus between the steel casing and the surrounding rock has been filled with cement to create a continuous cement sheath. The primary purpose is to provide zonal isolation, mechanical support for the casing, and protection of freshwater zones from crossflow. A well that is well cemented is more resistant to formation fluids migrating along the wellbore and to corrosion of casing caused by aggressive formation fluids.

Applications span oil and gas wells, geothermal wells, and some groundwater or storage wells where isolation of multiple intervals is required. Cementing is typically performed during primary cementing after casing is run but before perforations are made, using a cement slurry designed for the downhole temperature, pressure, and formation conditions. The job may involve centralizers and paddles to ensure an even cement sheath, stage cementing for long sections, and various additives to control viscosity, fluid loss, set time, and ultimate strength.

Quality control relies on downhole log data and surface tests. Cement bond logs and ultrasonic tools assess whether the cement is bonded to casing and formation; pressure tests, temperature surveys, and borehole imaging help detect channels or micro-annuli.

Common failure modes include poor centralization, mud losses, channeling, gas migration, and inadequate bonding. Remedial options include squeeze cementing, cement plugs, or re-entry cementing in a revived zone.

In summary, well cemented denotes a borehole where a properly designed and placed cement sheath provides long-term zonal isolation and structural integrity under operational conditions.