In horizontal drilling, the well is first drilled vertically, then at a specific target depth the well is turned and drilled horizontally through the oil or natural gas deposit. Next, the rock formation is fractured to allow the oil or natural gas to flow to the surface through the well. Horizontal drilling is an important innovation because oil or natural gas can be trapped in geological formations that have very tiny pore spaces within the rock (called “tight” formations). Horizontal drilling and hydraulic fracturing are used to economically produce trapped oil or natural gas. Tight formations are found throughout Western Canada. The Montney area (northeastern British Columbia and northwestern Alberta) and the Duvernay (Alberta) are two large Canadian development areas where this production method is widely used.