While steel casing serves as the primary shield to underground energy in all its forms (pressure, gases, underground water, etc.), specially prepared cement is used to create a pressure-tested seal between each layer of casing. Only a properly executed cementing job can fully guarantee the safety and well-being of everyone on site, as well as the surrounding environment.
This diagram underlines the basic components of a cementing job:
Oil and natural gas well cementing job (Image credit: API)
A) In between each layer of steel casing is a space that must be filled to hold the casing in place securely and create a solid, sealed barrier between the well and the surrounding forms of energy (gases, pressures, underground water, etc.).
B) Specialized cement carefully designed for the well's conditions is then introduced as a form of glue to seal the casing layers together.
C) The cement is pumped down the interior of the casing forcing the cement up from the bottom of the well until it completely fills the space between the outside walls of the drilled hole and the steel casing.
Cement Job Verification
Together, multiple layers of cemented steel casing provide a redundant barrier to isolate the surrounding energies.
(Image credit: API)
Testing the quality of a cementing job is integral for any drilling operation. Drillers use multiple high-tech tools to verify that the cement's integrity matches the required standard, and that it has fully created a solid bond with the casing and the surrounding drilled hole walls. Only when the cement job is declared successful can the actual well production begin.