Active oil and gas pad on Bureau of Land Management lands near Canyonlands National Park, Utah.
Credit: Mike Duniway, USGS. Public domain.

A U.S. Geological Survey (USGS) study released this week on vegetation recovery at plugged and abandoned oil and gas well sites across the Colorado Plateau found that nearly one third of sites saw 50 percent of vegetation recovered compared to nearby reference sites after three to six years.

Using satellite, soil, and climate data, USGS authors examined 365 well sites in Utah, Colorado, and New Mexico for re-vegetation patterns. The well sites date from 1985 on and were abandoned in 1997 or later.

“The Colorado Plateau is an ecologically diverse region used for energy development, agriculture and recreation, including approximately 30 national parks,” said Miguel Villarreal, a USGS scientist and co-author of the study. “Understanding the factors that encourage successful re-vegetation is critical for resource managers to make informed decisions about this region of economic and ecological importance.”

According to USGS, more than 26,000 abandoned and 63,000 active oil and gas wells are located within the Colorado Plateau, a physiographic desert region centered on the Four Corners that covers Colorado, Utah, Arizona, and New Mexico.

“Landsat imagery and other observational data can be instrumental in identifying sites at risk of poor recovery and help inform strategies to improve successful reclamation following oil and gas development in the Colorado Plateau,” said Villarreal.

USGS said that the study used a “top-down” view of soil surface covered by plants, or “vegetation cover,” on abandoned well sites, which they then compared to reference sites located nearby that did not contain any wells. They then calculated a “relative recovery of vegetation.”

“There was a wide range of re-vegetation among the sites. After five years of recovery, vegetation cover on well sites was 36 percent of that found on reference sites, on average. About half of the well sites in the study contained less than 26 percent vegetation cover found on reference sites. About one third of the well sites had more than 50 percent of the vegetation cover found on reference sites. The USGS has initiated a number of studies to better understand what restoration techniques are working, which are not, and where,” the USGS wrote.

The agency attributed some of the variation in re-vegetation to differences in precipitation received in the dry, desert region. They noted that wet years coincided with relatively high rates of vegetation recovery, while dry years were strongly associated with lower re-vegetation levels.

There also was a difference between well sites’ naturally occurring local vegetation and rates of recovery. The strongest areas of re-vegetation were found primarily in grasslands, while abandoned well sites located in shrubland or pinyon pine-juniper woodlands recovered at a rate half that of the grassland well sites.