Which term refers to a well that hasn't been used for more than 12 months?

A well that hasn't been used for more than 12 months is referred to as an abandoned well. This term specifically defines a situation where a well is no longer actively used for extracting water or other resources and has become inactive. In environmental and drilling contexts, such wells may pose risks of contamination or safety hazards, as they can allow pollutants to enter groundwater if not properly sealed or maintained.

Monitoring wells, on the other hand, are specifically used to observe water levels, quality, and other parameters. Dewatering wells are designed to remove groundwater from an area, often to facilitate construction or mining operations. Test wells are drilled to gather data about subsurface conditions but are typically used continuously for a defined period. Each of these terms has a distinct purpose that does not encompass the definition of an abandoned well.