Legacy wells are those oil and gas wells that were drilled many years ago and are still producing hydrocarbons. These wells are often described as conventional wells, and they are typically found in mature producing basins. Synonyms for legacy wells include mature wells, conventional reservoirs, older wells, and mature basins. These terms are used to describe wells that have been producing for many years and are still economically viable. Legacy wells are often located in areas that have a long history of oil and gas production, such as the Permian Basin in Texas, where many of the older wells are still producing.