Horizontal drilling is a method of creating wells for water, oil or natural gas by altering the usual vertical angle of the well. By drilling sideways, the well can increase the "pay zone," thus increasing the amount of oil that is retrieved from the well.
Horizontal drilling is especially useful when drilling in areas that normally can't be reached, such as underneath a highly populated area. It can also be used to drill a broad area from a single drill pad. Horizontal drilling can also relieve pressure from overloaded wells by dividing the incoming oil between two pads. Additionally, it can increase production in areas where reservoirs are fractured into small pockets.