For the first time, scientists have mapped groundwater variables nationally to understand which aquifers are most vulnerable to contamination from orphan wells.  Oil and gas wells with no active owner that are no longer producing and have not been plugged are considered orphan wells. These unplugged wells can create pathways for contaminants like hydrocarbons and brine to migrate from the oil and gas formation into groundwater zones. … USGS scientists Joshua Woda, Karl Haase, Nicholas Gianoutsos, Kalle Jahn and Kristina Gutchess published a geospatial analysis of water-quality threats from orphan wells this month in the journal Science of the Total Environment. They found that factors including large concentrations of orphaned wells and the advanced age of wells make aquifers in Appalachia, the Gulf Coast and California susceptible to contamination.