Identifying Emitters
Colorado State University (CSU) has conducted a study measuring methane emissions and evaluating the effectiveness of well plugging. The data collected will be used to prioritize abandoned and orphaned well plugging efforts. Colorado has just under 1,000 wells in the orphaned well program list.
From August 2022 to April 2023, CSU researchers surveyed wells in 17 counties and across 63 production areas, measuring methane emissions from 108 plugged and abandoned wells and 226 unplugged and abandoned wells. They also revisited 36 of the sites several months later to re-check the wells for methane leaks and confirmed that there were no methane emissions from the plugged wells.
The study’s findings were discussed at an October 2023 meeting with the Energy and Carbon Management Commission (ECMC) which maintains an Orphaned Well Program to help oversee Colorado wells.
Importance of Plugging
While the study showed that plugged wells are a methane success story, many recently abandoned wells were large methane emitters. Additionally, three wells in Adams County were reported to be releasing disproportionately large amounts of methane. How much? One of the three wells was emitting 75 kilograms of methane per hour.
The average methane emission rate for a well in Adams County is 1.24 kilograms per hour and for other Colorado counties about 0.0325 kilogram per hour. A dairy cow on average releases about 0.04 kilograms of methane per hour.
Adams County has about 300 orphaned wells. According to the research, shut-in wells are the primary source of methane emission in the county. They were stripper wells (15 BOE/day production), and when operators went bankrupt or discontinued operations, they production ceased but the wells were left unplugged.
The 2018 shutdown of the Third Creek gathering system (which collected natural gas in Adams, Arapaho, Elbert, and Denver counties) pushed many small operators of marginal wells out of business, leading to over 200 Adams County wells being shut-in or added to state orphan well programs. The methane emissions average for these newly orphaned wells is on average 3.64 kilograms of methane/hour.
Prioritization by the Numbers
Colorado will consider fugitive methane emissions when prioritizing plugging, and the CSU study will be added to the Orphaned Well program database and the ECMC’s own measurements.
As of 2023, wells with methane emissions over 0.1 kilogram per hour will be the plugging priority: there are 18 wells on the orphan program list at this level. Adams County boasts eight, with four already plugged. La Plata County has three, Mesa and Rio Blanco County each have two, and Logan, Weld, and Moffat each have one of these wells.
The next priority – wells emitting 0.01 to 0.099 kilograms of methane per hour. Adams County has 25 of the 39 wells in this category.
Counting on Technology
Recent federal funding has allowed more modern monitoring tools for inspectors, who previously relied on traditional “sight, sound, smell” and infrared cameras to detect leaks. Prioritization based on real data allows resources to be utilized more effectively to reduce methane emissions.
Resource Conscious Remediation
While many wells are relatively straightforward to plug and abandon, some wells require intensive remediation that can quickly balloon costs and jeopardize entire budgets. Fortunately, new technologies like BioSqueeze® are enabling efficient abandonment on even the most difficult wells.
