(1) With SP and resistivity logging. It is the conductor line, to which is attached a portable surface electrode, which is extended to some remote location from the rig and logging unit to provide electrical ground connection.

(2) With perforation safety. Ground strap. It is a heavy-gauge, low-resistance line provided with appropriate connectors or clamps to electrically connect together the masses of the hoist unit, rig, and surface casing (wellhead). This negates voltage differences which may occur between the masses.