Which type of casing is referred to as 'conductor casing'?

Conductor casing refers to the first pipe that is set in a borehole. It plays a crucial role in the drilling process as it helps to stabilize the borehole and protect the subsequent drilling operations from surface conditions. The conductor casing is typically installed relatively shallow and serves to prevent the collapse of shallow layers of soil and rock while also protecting against contamination from surface fluids.

This type of casing often extends through unconsolidated materials and allows for a clear pathway for the drilling rig's other operations. By setting the conductor casing first, it ensures that the deeper, more specialized casings can be installed safely and effectively, enabling the drilling process to advance through more difficult subsurface geological conditions.