Surface casing: install the
oil casing head on the top, suspend and support the subsequent layers of the casing through the casing head; isolate the surface shallow water layer and the shallow complex bottom layer, so that the freshwater layer is not polluted by drilling fluid
Intermediate casing (technical casing): isolate formations with different formation pressures or complex formations that are prone to collapse and leakage.
Production casing: protects the production layer and provides a channel for oil and gas to flow from the production layer to the surface.
Drilling liner: reduce the load of the drilling rig when running the casing and the load of the casing head after cementing, save a lot of casing and cement at the same time, and reduce the cementing cost.
