A wellbore is a deep, vertical shaft drilled into the earth's subsurface with the primary intention of mining petroleum, natural gas, or other minerals. These wells are often located in the underground and are formed through a combination of drilling and then completing the boreholes. The purpose of a wellbore is to create an environment conducive to the extraction of oil or gas from the surrounding rock formations.

The configuration of a wellbore can vary depending on factors such as the size and shape of the geological formation, the type of rock formation and the type of material being extracted. For example, a wellbore used for a gas well might be configured differently than one used for oil or mineral extraction. Depending on the specific situation, a wellbore might be uncased or might encased in a cement and steel casing.

A wellbore's life is divided into two stages – drilling and completion. In the drilling stage, the pilot hole is constructed and the drill is then used to form the wellbore. While drilling, the material is carefully examined to determine how deep to drill, the type of material being extracted, and the type of formation being penetrated. A variety of tools can be employed during this stage, such as a casing running tool, directional drilling motors, and drill bits.

The second stage is completing the wellbore. Completion operations involve positioning the production tubing, sealing the wellbore, and connecting the wellbore to the production equipment. The production tubing is used to allow the oil and gas to flow from the underground formations into the wellbore, and the sealing process is a critical operation to prevent contaminates from entering the well. Completion operations might also include operations such as fracking, acidizing and perforating.

The life of a wellbore can sometimes be extended with the use of treatments and processes that enhance the fluid flow from the rock formation. For example, acidizing and perforating can be performed to create micro-fractures in the formation, or drilling mud can be used to increase pressure at certain depths and reduce pressure at others. These treatments and processes can improve the rate of production and in some cases even extend the life of a wellbore.

Overall, wellbores are a critical part of extracting oil and gas. They can vary in size and shape and are used in a variety of contexts, but they all serve the same purpose - providing an environment conducive to oil and gas extraction. These shafts are often complex, and the operations required to complete and maintain them demand expertise and small tools which require precision. Thus, the knowledge and skill necessary to create and maintain a wellbore that is efficient and safe is paramount.