The casing string that is usually put into the well first, particularly on land wells, to prevent the sides of the hole from caving into the wellbore. This casing, sometimes called drive pipe, is generally a short length and is sometimes driven into the ground. Conductor pipe is run because the shallow section of most wells onshore is drilled in unconsolidated sediment or soil rather than consolidated strata typically encountered deeper. Offshore, the drive pipe or structural casing may be installed prior to the conductor for similar reasons.