2) Horizontal drilling. For horizontal drilling, the well bore (the hole the well
makes under the ground) is drilled vertically, then turns to travel horizontally
through the target layer; thus, horizontal drilling. This allows each well to come in contact with, and therefore fracture, a larger amount of the formation. See Figure 1. This is especially useful in thin layers,
like the Marcellus Shale. It requires far more water to hydraulically fracture a
well that travels horizontally through a gas-bearing
layer it takes to hydraulically fracture a vertical well – millions of gallons compared to
tens or hundreds of thousands of gallons – thus, high volume.