Horizontal drilling

From Wikimarcellus

In order to tap natural gas with horizontal drilling typically a drill is sent down vertically a mile or so underground and then turned at a ninety degree angle horizontally into the shale.

Horizontal wells are much more expensive to drill than vertical ones. Costs may run between $4 million and $7 million U.S. for a horizontal shale well. Vertical wells can be drilled for only $1-2 million U.S.