A well is a structure that is drilled into the ground for several purposes.
We will discuss two basic types of wells throughout this lesson. They are known as 1) extraction wells and 2) injection wells.
Extraction wells, also known as recovery wells, are drilled for the purpose of accessing natural resources, such as:
- Extraction of water
- Sampling of rock or soil
- Extraction of mineral resources, like oil and gas
Injection wells are used for injecting a number of different materials for various purposes, such as:
- Injection of wastewater or other waste fluids
- Injection of water for secondary oil recovery
- Injection of CO2 for enhanced oil recovery
As showcased in the figures above, the same material can be considered a resource we extract, or a waste product we dispose of through injection. For example, artesian wells (top figure) are typically drilled to extract water stored in pressurized, confined aquifers. In contrast, we can drill an injection well into a confined space below ground to dispose of wastewater, such as stormwater runoff (bottom figure).