What Does Casing Seat Mean?
A casing seat is the point at which the casing is set into an impermeable and stable formation. The casing is the structural component of a wellbore that protects the wellbore from caving and enables entry and exit of downhole equipment and production lines. The casing is cemented to the side of the borehole and is designed to withstand aggressive chemicals and forces acting on them.
Casing protects fresh water formations in the region and isolates lost return zones.
Trenchlesspedia Explains Casing Seat
Appropriate casing seat selection depends on correct assessment of pore and fracture pressures present throughout the well. Further casing string will be necessary if during drilling of a formation, the pore pressure approaches the fracture pressure. The casing setting depth is selected by clearly defining the well objective, and listing real and potential problems that nearby wells have encountered.
When intermediate casing seat is required, factors to be considered are: consideration of differential pressure to safely lower the casing; isolating unstable formations such as lost circulation zones and heaving shales; length of the open hole.