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New Mexico State University

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NMSU tests vegetation mixture for San Juan Basin gas well reclamation

FARMINGTON - New Mexico State University's Agricultural Science Center at Farmington has played a key role in improving the success of revegetation efforts on land disturbed by oil and gas exploration in one of the most prolific gas producing regions in the United States.



Richard Arnold, professor of weed science at NMSU's Agricultural Science Center in Farmington, looks at wheatgrass that he has recommended for use on the revegetation efforts in northwest New Mexico that have been disturbed by oil and gas drilling. (NMSU Photo by Jane Moorman)

The San Juan Basin's 29,000 wells, atop an underground area encompassing 15,000 to 20,000 cubic miles of sedimentary rock, produce approximately 70 percent of the natural gas in New Mexico. While New Mexico Energy, Minerals and Natural Resource Department's Oil Conservation Division governs the drilling site activities, the Bureau of Land Management (BLM) regulates how the land is left after drilling is completed. BLM wants the work to be done in an environmentally responsible manner to prevent erosion and wildlife habitat fragmentation.

"We want to stabilize the soil to prevent erosion and return the land to some level of productivity for other uses," said Steve Henke, district manager of the Bureau of Land Management Farmington office.

To reach that goal, soil disturbed by wells and pipelines must have native and non-native grasses reestablished. This requires the oil and gas producer to contour the land and plant a select mix of grasses. BLM requires this process annually on an average of 500 new wells and associated pipelines. BLM found that it needed a mixture of native grasses that would survive the harsh environment of the arid Four Corners region.

"We had three seed mixtures identified, depending on the geographic area," said Henke. "But we were showing varying degrees of success. We turned to NMSU to help us improve our success rate."

BLM, several oil and gas producers in the region and the cattle growers association in San Juan County funded a project with NMSU's Agricultural Science Center at Farmington to determine what native grasses should be planted.

Richard Arnold, college professor of weed science at the center, conducted a three-year study to find a variety of grasses that are adaptive to soil and climate of New Mexico's northwest Four Corners region. The study required that the plants had to germinate and grow using the brine water extracted from the coal-bed methane gas well sites.

"Our goal was to determine what seeds can germinate with coal-bed methane produced water, what plants can survive with a limited amount of water and what type of herbicide works best with the plants when battling noxious weeds," Arnold said. "That's the magic mix."

Arnold conducted a test of 16 native and non-native grasses to determine which would germinate and grow with the brine water.

"We came up with a mix of grasses that are very tolerant to high levels of salt while being established. We only put on four to eight inches of produced (brine) water, depending on the soil type. Once we get the grass established, then the plant is on its own and has to survive with the available rain fall," Arnold said.

The grass mix Arnold suggested to the BLM includes Arriba Western Wheatgrass, Hy Crest Crested Wheatgrass, Bottlebrush Squiretail, Paloma Indian Ricegrass, San Luis Slender Wheatgrass and some Four-Wing Saltbush. Once the grass mix was determined it was tested on six well sites. BLM has established a specification regarding the quantity of each type of grass required at each disturbed site.

"We cut the cost of the seed being used because we developed a mix that really works out in the oil patch. Granted, it all depends on rain once the stand is established," Arnold said.

"Despite the harsh environment in northwestern New Mexico, we're seeing good results now that the drought has broken and we are back into a more traditional rainfall pattern," Henke said. "We're starting to see results from our seeding efforts."

One benefit to the reclamation project is that the habitat's vegetation is better than it was prior to the land being disturbed.

"Prior to drilling, the vegetation was mainly sage brush," Arnold said. "Now we have grass coming up where sometimes there was nothing. Grass controls soil erosion while sage brush will not. But, we didn't get rid of all the sagebrush because it is important in a deer's diet. As we studied the grasses, we also had to be sure it was palatable for wildlife and domesticated cattle."

"I think the ranchers appreciate the work we've done as well as many of our wildlife, particularly the elk. We see elk on these reseeded areas frequently," Henke said