Also called swamp barge. See floating offshore drilling rig . Mud can be pumped in but flow back up the stem is prevented. Also called an internal blowout preventer. Insulating flanges are often used in cathodic protection systems to prevent electrolytic corrosion and are sometimes installed when a flow line is being attached to a wellhead.
Interfacial tension is caused by the difference in fluid pressures of the liquids.
Keeps hole from caving and seals off troublesome formations. Also called protection casing .