How Gas Wells Release Methane Into Groundwater

Full report here: How Gas Wells Leak Into Groundwater

The DEC’s proposed “enhanced requirements” for well construction will not keep Upstate drinking water from being gassed. Gas wells leak methane from the outside of the casing up, then from the inside out. As they rust out, all gas wells will eventually leak into groundwater. The only viable solution is adequate setbacks of gas wells from drinking water sources. Gas well setbacks in New York are the worst in the United States.[1]

The DEC’s proposal to require a 3^rd casing in gas wells will not solve the chronic problem of gas wells leaking methane into groundwater. This is due to three factors, none of which are solved by additional casings :

1. Methane is mobilized during the drilling process. Every drill bit is operating in an uncased well-bore and any gas it encounters is going to be circulated up via drilling fluid through uncased sections of the well-bore. Most of this gas is captured by the gas separating unit (degasser) on the drill rig, but not all of it.

2. Methane is released on the outside of the outermost casing.[2] The outermost layer of cement will not adhere to certain types of rock, including shale. Cement shrinks and cracks over time, causing gaps to form that allows gas to flow upwards between the casing and the rock. Once this starts to happen, the well bore itself becomes a pathway for methane to pollute groundwater. See Figure 1 which illustrates how gas channels up between the outer casing and the surrounding rock.

3. All gas wells will eventually rust out and leak. Not a matter of if, only a matter of when and how much. Unplugged wells will leak faster than plugged ones.[3] Some well leaks can be repaired from the inside. Many wells will leak on the outside of the casing, which defy repairs.[4] The Wall Street Journal reported that 1in 10 new gas wells tested in Pennsylvania leaked. On a 10 well drilling site, the odds of leakage approach 100%.[5] Over time, they are all apt to release methane into groundwater.

Evidence of such leaking can be observed within the casinghead at the bradenhead gauge as well as in the surrounding soil. Sustained casinghead gas pressures are common in the industry; indeed they are a chronic problem, which indicates that by the 5^th year, 25% of the wells tested were leaking, and by the 8^th year, 40% of the gas wells tested were leakers.[6] In the proper conditions, gas wells leak. And all of them will leak eventually. Gas well leakage has been known to the industry for decades. The amount of leakage is immaterial from an economic standpoint – particularly if the gas channels up the outside of the outermost casing. But such releases can easily contaminate groundwater.

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Tagged as: gas wells, methane, New York, United States