Core sample taking unit lowered in drilling string - has telescopic core barrel extended by mud pressure on piston of barrel inside unit

摘要

Unit comprises a cylindrical tube lowered down the string and contg. a sampling barrel and sealing means to prevent entry of drilling mud into the annular space between tube and string and act as stop for the tube. Means are provided which telescopically extend the barrel below the lower end of the string under the action of mud pressure to take a core sample. Pref. tube has a closed upper end with ducts for pressurising its interior, a cable coupling and an external ring to centralise it in the drilling string which may have a bit at its lower end.