Directional Drilling - also called Horizontal, Deviated, or Slant Drilling - is the process of drilling a curved well, in order to reach a target that is not directly beneath the drill site. Although the technique has been around since 1939, early applications were severely limited by low build rates and short lateral extension capabilities. Deviated drilling, also known as slant drilling, is a fairly old method in which it often took up to 2,000 feet for the well to complete the transition from vertical to horizontal. Modern horizontal drilling, however, can make a 90 degree turn in only a few feet!
Increased Recovery Rates and Extended Production Life - Horizontal wells generally increase productivity to at least 2-3 times that of vertical wells. For wells which would have otherwise been considered marginal or uneconomic, horizontal drilling often enables successful reservoir development. There are many kinds of reservoirs where the potential benefits of horizontal drilling are obvious.
Reduced Capital and Operating Costs - In addition to draining the same amount as three or four vertical wellbores, a horizontal well costs significantly less than drilling several vertical wells in the same area. The operating costs associated with infrastructure, wellhead equipment and maintenance are also significantly reduced.
E&P technologies have literally redefined reserves. Oil and gas at depths recently considered unreachable can now be tapped. Smaller accumulations once thought to be uneconomic can now be produced profitably. Fields under wetlands or cities can be accessed without disruption of the surface" (U.S. Department of Energy)
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