The world of oil and gas drilling can be confusing at the best of times, with all the jargon making reports a difficult task to decipher for the untrained eye.
To make matters even more complicated, there are several different types of ‘wells’ that an oil and gas exploration company will refer to.
Different wells will be used at different stages and for different purposes of an oil drilling process.
Here’s a rundown of some of the most common types of wells and their purpose.
What is a well?
First, it would be beneficial to explain what a ‘well’ is in this context.
Essentially, an oil well is a hole dug into the Earth, onshore or offshore, with the purpose of bringing oil below the surface, above it, with the end goal of commercialisation.
Wildcat well
A wildcat well is often the riskiest type of well, but can also be the most rewarding.
When drilling a wildcat well, an exploration company will drill in unproven or fully exploited areas that either has no historic production records or it is believed to be completely exhausted as a reserve.
Exploration well
An exploration well is the starting point, at least when it comes to drilling into the ground.
Oil and gas companies will drill an exploration well in a new area to locate proven reserves.
Before that, however, data concerning rock and fluid properties in the region, reservoir pressure and geological data is collected before the ground is broken.
Appraisal well
An appraisal well is used to give more detailed information about the area, specifically the extent and size of a deposit that has initially been discovered during the exploration phase.
Development well
Once a potential deposit has been identified and appraisal has taken place to identify exactly what the company has on its hands, a development well will be installed.
A development well will be drilled in a proven area and is a generic term used for the different ways in which a resource can be extracted.
Horizontal well
A horizontal well is a technique of extraction that has become increasingly popular in recent years.
Here, a well is dug at an angle of at least 80 degrees to a vertical wellbore, which is the hole that forms the initial well.
Often, this type of well is used in situations where the shape of the reservoir is difficult to access from above the surface.
The method has become more and more popular as the technology advanced, making it cheaper and more efficiently to drill this type of well.
Horizontal wells have also been helpful to hydraulic fracturing, or fracking, allowing oil and gas companies to access difficult-to-break areas.
Vertical well
As the name suggests, a vertical well involves drilling vertically into the ground, and is considered the more traditional method of oil extraction, although the rise of horizontal drilling means the method has become less common.
The method is often used to extract oil directly below the well site, with its primary benefit being it is relatively simple compared to other methods.
However, if the subsurface reservoir extends horizontally, multiple vertical wells will need to be drilled to access the entire resource.
Sidetrack wells
A sidetrack well is used in horizontal well and is essentially an additional wellbore drilled at another location to the first wellbore.
Multilateral wells
A multilateral well is the same as a sidetrack well, except there is more than one additional wellbore.