When I think of oil drilling I imagine a long vertical oil well reaching deep down into the earth– never deviating from its up-and-down direction. It makes sense to think of it this way, and for the longest time, that’s the only way we drilled–vertically.
However, oil reservoirs often extend horizontally throughout the earth’s crust. They’re not just found in pockets, they’re also found in large “pools” that can extend for large distances underground.
To get technical, vertical wells resemble an “I” shape, and horizontal ones look more like a “J.” Because of its design, vertical wells only absorb the oil or natural gas immediately surrounding the end of the well. As you can guess, this isn’t very efficient at all.
But that’s how we used to do things for a long time! In fact, up until the late 1920’s we used to drill multiple vertical wells to drill the same reservoir.
That changed after better technology was developed.
Despite being more efficient, it’s more complicated to drill a horizontal well. First, the driller discovers how deep the reservoir is, then he inserts a special bit assembly underground that he’s literally able to track. After that, the driller gradually angles the assembly to form that “J” shape, reaching further and further into the reservoir.
This provides much more contact with the reservoir than a traditional vertical well, and is a pretty cool feat of engineering at the same time.