How crude oil is drilled
The earliest known oil wells were drilled in China in 347 CE with bits hung on bamboo poles.
- stations
- 4
- things downstream
- 492
The short version
Crude oil is the thick, dark remains of ancient plankton and algae, trapped in rock deep underground. A drilling rig spins a steel bit down through the layers, and steel pipe called casing is cemented into the hole as it deepens. When the well reaches the oil, pressure and pumps bring it up to the surface.
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Pick the target
Geoscientists and engineers work out what rock the well will pass through and where the oil should sit. They plan the path so that the bit meets the reservoir without hitting zones that would be unsafe to drill.
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Spin the bit down
A rig rotates a long string of pipe with a bit on the end, boring a hole from 12 centimeters up to 1 meter wide. Modern directional drilling lets a well turn from vertical and run sideways through a thin layer of oil-bearing rock.
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Case and cement the hole
At set depths, sections of steel pipe slightly smaller than the hole are lowered in and cemented into place. Each casing isolates the rock behind it, and the well can then continue deeper with a smaller bit.
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Bring it to the surface
Oil rises on its own pressure at first and is lifted with pumps later. Some natural gas usually comes up with it, and the oil is sent off to be refined.
Worth repeating
- An estimated 70% of the world's oil deposits formed in the Mesozoic era.
- Edwin Drake drilled a famous early oil well in Pennsylvania in 1859.
Where it goes next
Crude oil feeds 17 lines directly and reaches 492 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How crude oil is drilled." Assembly Line, 2026-11-03. https://assemblyline.org/make/crude-oil