Drilling an oil well can take anywhere from 15 days to 12 months, sometimes longer. The amount of time it takes depends on a number of different factors, including the depth of the well and whether it's on land or offshore.
Whether the well is being drilled using vertical or directional drilling also plays a role in how long it takes to complete the project. In the past, it was common for wells to be drilled as vertically as possible. However, directional drilling is an important advancement that has allowed oil companies to begin developing new deposits, such as North Dakota's Bakken formation. In directional drilling, the well is usually drilled vertically for up to 2 miles, then the drill bit is angled so the well passes directly through the oil-containing formation for up to 2 miles.
A typical directional well in the Bakken formation can usually be drilled in between 15 and 30 days, whereas offshore well drilling could take up to a year. When wells are being drilled, the drilling company usually works 24 hours a day, seven days a week until it's finished. After the well is drilled, it's necessary for a completion crew to come in to prepare the well for production, which typically takes another 30 days or so.