Oil and Gas

How petroleum is extracted

An oil well is constructed by an oil rig drilling a lengthy hole into the ground. To offer structural stability to the newly drilled well bore, a steel pipe (casing) is inserted into the hole. The well's base is then drilled with holes to allow oil to flow into the bore. Finally, a "Christmas tree" of valves is attached to the top; the valves regulate pressures and control flow.

• 
  Primary recovery


• 
  Secondary recovery


• 
  Enhanced recovery