While some oil
wells contain enough pressure to push oil to the surface, most oil wells drilled
today require pumping. This is also known as artificial lift.
If a well
requires it, a pump is lowered down the tubing to the bottom of the well on a
string of steel rods, referred to as the rod string. The rod string is hung from
the wellhead and connected to a drive unit and motor on the surface. The rod
string conveys power to the pump either by rotating or moving up and down,
depending on the type of pump employed. Submersible pumps are used on some
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.