By technical definition, a well is a hole drilled in the ground to obtain geological information, find and produce oil or gas, or provide service to the operation of an oil and gas property.
The wellhead refers to the equipment at the top of a well casing that is used to maintain the surface control of the well.
How it’s important to us
I know that these terms probably seem obvious, but I included them both so that we understand the distinction. We often use the term “well” to mean a variety of things that aren’t technically correct. It’s also important to realize that a well does not necessarily mean it’s a hole extracting hydrocarbons (it could be salt water disposal, for example). Also, you often hear people in the business refer to the “wellhead”, particularly when discussing allocations.