Definition - What does Intermediate Casing mean?
Intermediate Casing is the casing which is generally set in place before production casing and after surface casing to provide protection against the abnormally pressured or weak formations. The casing enables the use of drilling fluids with different density crucial for controlling the lower formations. It is generally set in transition zone from the normal pressure to the abnormal pressure. It is often considered as the longest section of the casing present in a well. Most of the wells are drilled with running an Intermediate Casing.
Petropedia explains Intermediate Casing
The Intermediate Casing is essential on longer drilling intervals where the essential weight of the drilling mud used to prevent well blowouts that can result in hydrostatic pressure which can fracture deeper or shallower formations. This casing placement is preferred to make the hydrostatic pressure of the drilling fluids to remain at a pressure level between the fracture pressure and formation pore pressure. They are set when the borehole conditions or the geological characteristics need isolation. The conditions include, but are not limited to, formation fluid influx, hole instability and prevention of the lost control. It is possible to run multiple Intermediate Casings in a single well.