Throughout California and other parts of the country, thousands of abandoned oil and gas wells remain unplugged. Some have even had buildings or parks built on or around them.
Some wells were never plugged, and some plugged ones have failed, leaking oil, natural gas, and formation fluids. Yet addressing this issue has been largely postponed. When leaking wells are found often nothing is done, allowing greenhouse gasses to escape, and impacting groundwater quality.
Non-producing wells should be sealed to prevent oil, natural gas, and fluids from escaping the geological formation. Plugging helps prevent groundwater contamination and air quality degradation.
California regulatory data shows 122,466 plugged wells in the state: Determining how many are improperly plugged is difficult. In 18,000 older wells, about 70% were drilled prior to 1980 and risk well casing failures and groundwater contamination.
Of 245,000 older wells in California databases, it is estimated 80,000 are improperly plugged or unplugged, emitting volatile organic compounds (VOC) and other contaminants.
The issue is not unique to California. Nationally, an estimated 2.56 million oil and gas wells have been drilled and 1.93 million wells had been abandoned by 1975. The EPA estimated in 2016 there were 2.15 million unplugged abandoned wells in the U.S.
The density of aging and improperly plugged wells is a major risk for development of California’s oil and gas fields. When old wells are reworked, the injection of fluids and gas increases pressure in a reservoir. Poorly plugged or aging wells often lack integrity and formation fluids can migrate up the wellbores, bypassing existing plugs.
In a 2014 report, the U.S. Geological Service warned the California State Water Resources Control Board that the integrity of abandoned wells is a serious threat to groundwater sources.
Abandoned wells create a pathway for methane and fluids to escape. In Pennsylvania, Texas, and California, many wells remain unplugged or with rudimentary cement plugs in place. Permanently sealing these wells requires modern solutions such as biomineralization.
New requirements incentivizing operators to plug and abandon idle wells will help to reduce the number of orphan wells, but does not address existing orphan wells left unplugged.
Clearly it is time for state and federal governments, in cooperation with the energy industry, to take action on funding and managing abandoned wells. Plugging and sealing wells correctly with advanced materials should be recognized as a “best practice” approach to reducing methane emissions and mitigating other risks.
