99
abandoned wells, which are present anywhere people drilled for oil and gas, extending clear back to 1859 and our old friend Colonel Drake. Most of these older wells
are not in state well records, which were not established until after the Second
World War, and many have not been located. Quite a few still leak significant
amounts of methane into the atmosphere (Kang et al. 2014, 2016).
The U.S. Department of Energy has employed magnetic survey techniques and
methane sensors to try to locate abandoned wells in urban areas, but the presence of
other infrastructure can interfere with and complicate the measurements (Hammack
and Veloski 2016). For larger areas such as developed oil fields in places like
Wyoming, magnetic booms deployed from helicopters have been used with a degree
of success (Hammack et al. 2016). The magnetic survey reacts to steel and iron casing remaining in the ground from abandoned wells, even if casing was cut off level
with the surface, and the well was subsequently overgrown and buried. This was
common practice on abandoned wells, and a significant amount of digging into the
center of magnetic anomalies is often required to actually locate the old wells. Many
abandoned wells also had the casing pulled to meet the high demand for steel during
the Second World War. Although it was feared initially that this would compromise
the magnetic surveys, researchers discovered that the void spaces in the Earth
remaining from the uncased wells often register as magnetic anomalies on the surveys, allowing the boreholes to be found (Hammack et al. 2016).
Modern regulations were not put into place for how to properly P&A a well until
the second half of the twentieth century, and many older wells were abandoned
rather creatively. A common technique in the Appalachian Basin back in the day
was to stuff a small pine tree down the borehole pointy end first, and then shovel in
dirt on top of it. (An 1881 Pennsylvania state regulation actually specified the use of
a “tapered wooden plug,” which could be argued is a pine tree). Although this served
to hide an old well, it did not provide much of a pressure barrier. In other cases
where modern P&A practices were carried out, bridge plugs were sometimes not set
properly or poor-quality cement was used.
Although state regulators do commonly provide oversight of the plugging operations, shortages of personnel rarely allow inspectors to visit sites after the well has
been plugged. For many operators, proper P&A is a professional duty, but to others
it is just a needless expense that must be taken care of as cheaply and quickly as
possible. Unfortunately for shale well drillers, the long history of O&G drilling in
the United States means that they could encounter a wide variation in the quality of
P&A wells in the neighborhood.
Finding definitive links between stray gas and fracking has been challenging.
Data mining of groundwater chemistry information from Pennsylvania townships
where methane contamination had been reported provided some indications that
methane concentrations are higher in groundwater near gas wells and along faults,
but the results were far from conclusive (Li et al. 2016). Studies in northeastern
Pennsylvania suggest that local geological conditions may also play a role, and that
pre-existing structures and fractures in certain locations may allow methane to
migrate upward more easily (Woda et al. 2018).
6.1 Water Quality and Stray Gas
abandoned wells, which are present anywhere people drilled for oil and gas, extending clear back to 1859 and our old friend Colonel Drake. Most of these older wells
are not in state well records, which were not established until after the Second
World War, and many have not been located. Quite a few still leak significant
amounts of methane into the atmosphere (Kang et al. 2014, 2016).
The U.S. Department of Energy has employed magnetic survey techniques and
methane sensors to try to locate abandoned wells in urban areas, but the presence of
other infrastructure can interfere with and complicate the measurements (Hammack
and Veloski 2016). For larger areas such as developed oil fields in places like
Wyoming, magnetic booms deployed from helicopters have been used with a degree
of success (Hammack et al. 2016). The magnetic survey reacts to steel and iron casing remaining in the ground from abandoned wells, even if casing was cut off level
with the surface, and the well was subsequently overgrown and buried. This was
common practice on abandoned wells, and a significant amount of digging into the
center of magnetic anomalies is often required to actually locate the old wells. Many
abandoned wells also had the casing pulled to meet the high demand for steel during
the Second World War. Although it was feared initially that this would compromise
the magnetic surveys, researchers discovered that the void spaces in the Earth
remaining from the uncased wells often register as magnetic anomalies on the surveys, allowing the boreholes to be found (Hammack et al. 2016).
Modern regulations were not put into place for how to properly P&A a well until
the second half of the twentieth century, and many older wells were abandoned
rather creatively. A common technique in the Appalachian Basin back in the day
was to stuff a small pine tree down the borehole pointy end first, and then shovel in
dirt on top of it. (An 1881 Pennsylvania state regulation actually specified the use of
a “tapered wooden plug,” which could be argued is a pine tree). Although this served
to hide an old well, it did not provide much of a pressure barrier. In other cases
where modern P&A practices were carried out, bridge plugs were sometimes not set
properly or poor-quality cement was used.
Although state regulators do commonly provide oversight of the plugging operations, shortages of personnel rarely allow inspectors to visit sites after the well has
been plugged. For many operators, proper P&A is a professional duty, but to others
it is just a needless expense that must be taken care of as cheaply and quickly as
possible. Unfortunately for shale well drillers, the long history of O&G drilling in
the United States means that they could encounter a wide variation in the quality of
P&A wells in the neighborhood.
Finding definitive links between stray gas and fracking has been challenging.
Data mining of groundwater chemistry information from Pennsylvania townships
where methane contamination had been reported provided some indications that
methane concentrations are higher in groundwater near gas wells and along faults,
but the results were far from conclusive (Li et al. 2016). Studies in northeastern
Pennsylvania suggest that local geological conditions may also play a role, and that
pre-existing structures and fractures in certain locations may allow methane to
migrate upward more easily (Woda et al. 2018).
6.1 Water Quality and Stray Gas