The plugs in old oil and gas wells across Colorado are doing their job, preventing methane from escaping into the atmosphere — except in Adams County, which is home to several super-emitting wells, according to a Colorado State University study.
Adams County had three wells with massive emissions, the largest emitting 75 kilograms or 165 pounds of methane per hour, 142% more than the average for unplugged wells in the state.
“The CSU study is alarming,” Adams County Commissioner Eva Henry said in an email. “It is very apparent the health and safety of our community and the children in Adams County is in danger.”
The average methane emissions for the county were 1,240 grams per hour compared with an average for the rest of the counties surveyed of 32.5 grams per hour. By way of comparison one dairy cow, which belches methane, emits about 40 grams an hour.
Between August 2022 and April 2023 CSU researchers measured methane emissions from 108 plugged wells and 226 unplugged, abandoned wells in 17 counties and 63 oil and gas fields in Colorado.
There were zero emissions from the 108 plugged wells. “We didn’t see one plugged well that was emitting,” Stuart Riddick, a researcher at CSU’s Energy Institute, told the state Energy and Carbon Management Commission at an Oct. 16 meeting to review the results. The ECMC regulates oil and gas activities.
The CSU team went back after a few months and measured 36 of the wells again and the results were the same. The plugs were effective in both wells recently closed and those extending as far back as the 1960s. “Plugging in Colorado is effective,” Riddick said.
Wells shut in when operators walked away were worst emitters
The biggest emissions appeared to come from wells where production had stopped and the valves were closed, so-called shut-in wells.
“Shut-in wells are a potentially big risk, for they aren’t plugged and they aren’t serviced,” Riddick said. “If you leave anything outside for two years in Colorado it is going to corrode.”
“The biggest emitting wells were the newer recently abandoned wells,” Riddick said. “In some cases, these wells were not abandoned because they were played out, but because the owner ran into operating problems or went bankrupt.”
The orphan wells that were recently in production averaged 3,640 grams of methane per hour compared with 3.6 grams per hour for the remainder of the non-producing, orphan wells.
“This is a new type of orphan well,” Riddick said.
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The acute situation in Adams County was precipitated by Anadarko Petroleum shutting down its Third Creek gathering system, a network of small pipelines that collected natural gas from wells in Adams, Arapahoe, Elbert and Denver counties.
Anadarko, which was acquired by the Occidental Petroleum Corp., closed the aging pipeline system after a broken gathering line at a well in Firestone caused an explosion that leveled a home and killed two people in 2017.
Most of the wells in the Third Creek system were stripper wells — producing no more than the equivalent of 15 barrels of oil a day — operated by small companies. This led to wells being shut-in or abandoned to the state’s orphan well program.
There are 298 orphan wells in Adams County and three-quarters are on the Third Creek network, the county’s Henry said.
The state has made the level of fugitive methane emissions one of the criteria for ranking orphan wells for plugging and abandonment, Mimi Larsen, an ECMC deputy director, told the commission at the Oct. 16 session.
The CSU data will be incorporated into the state’s orphan well program and used along with measurements the ECMC is taking itself.
“It is our goal again to get those wells with larger emissions that have been measured plugged and abandoned as soon as possible,” Larsen said.
Wells emitting 100 grams of methane per hour prioritized
Starting this year, a well emitting 100 grams of methane an hour or more would receive the highest score for emission, giving them plugging priority. There are 18 wells in the orphan well program venting 100 grams or more per hour, Larsen said.
Eight of the wells are in Adams County, with four already having been plugged and four scheduled to be plugged. There are three wells in La Plata County and two each in Mesa and Rio Blanco counties. Logan, Weld and Moffat counties had one each.
All the wells have been or are scheduled to be plugged and abandoned, Larsen said.
The next highest priority group are wells leaking 10 to 99 grams of methane per hour. There are 39 wells in this category, with 25 in Adams County.
Not all unplugged wells present a problem. For example, the CSU study found five unplugged wells in Elbert County that had no methane emissions.
Until this year ECMC field staff had to rely on detecting methane emissions by their smell, sight or hearing (the sound of gas escaping from the well). An infrared camera could also be used to detect leaks.
As part of federal funding for orphan wells, the ECMC has been able to equip inspectors with more sophisticated methane monitoring equipment.
“We started using these technologies most recently with the grant monies from a well program from the Department of Interior,” Larsen said.
These included a microportable greenhouse gas analyzer.
“It is very frustrating to know that the gas and oil industry has made their fortune and left behind a very dangerous mess for the taxpayer to clean it up,” Henry said. “I hope with the partnership of the state and the Interior Department we will be able to address this problem.”