DEFINITION of Vertical Well
A vertical well is a borehole that is aimed directly at a target beneath it. A vertical well does not have a truly vertical borehole, but it is more or less aimed straight down at a reservoir of oil or gas rather than being turned horizontally at a designated point. Historically, natural gas and oil exploration involved the use of vertical wells because directional drilling technology was expensive and complicated.
BREAKING DOWN Vertical Well
Vertical well drilling is considered a conventional method of oil and gas extraction. Vertical wells differ from directional wells, such as horizontal wells, because they do not require the use of directional boring. This usually makes them less expensive to develop. Moreover, vertical wells have traditionally depended on the pressure on the deposit to facilitate extraction, something that is not possible in tight oil and other unconventional oil formations.
Vertical Wells Versus Horizontal Wells
While vertical wells may be less complicated to bring on line than directional wells, their limited angles make them less able to reach a wider section of underground territory. A vertical well can only access oil and natural gas reserves directly below, so making a large field productive often requires the drilling of many vertical wells at various points along the formation. By contrast, a horizontal well can be turned to run along the formation at depth. By running along the formation, a single horizontal well can access the same amount of oil that would have required multiple vertical wells to tap.
The End of Vertical Wells?
As conventional sources of oil and easy to tap reserves are being depleted, purely vertical wells are becoming less common. That said, horizontal wells still start with the drilling of a vertical well. In fact, a pilot hole and test holes will be drilled vertically so that engineers can examine rock fragments at different layers in order to determine where reserves can be found. This data is then used to model the reservoir and determine the kick off point. There have even been successful horizontal wells drilled to connect multiple reservoirs. The ability to efficiently extract one reservoir with a single well, let alone the ability to tap multiple reservoirs, yields massive cost savings in the long run. It also reduces the surface level disruption as not as many drill sites or derricks are required.
As the technology has improved, more and more wells end up being directionally drilled rather than solely vertical. In the sea, vertical wells are still the more common method as drilling from an offshore platform is already quite complex. That said, there is horizontal drilling taking place offshore and it will continue to grow if it yields more for the cost. Of course, the end of purely vertical wells is not the end of vertical drilling and vertical drilling rigs. They still start every borehole and will continue to be used for sampling on land.