Rock, teach oil, or maybe vice versa

GG attended a workshop here at CU on lessons from mining that could help guide oil and gas development (since the conveners encouraged outcomes to be shared on social media, figure this is OK). In kind of an odd way, the focus was more on what happens at the end of mining or oil development more than what happens at the start, so that will tend to be the focus here.

So a quick summary of points GG noticed.

  • Mining is highly focused, oil and gas far more distributed with a web of infrastructure.
  • Mines active today have to meet bonding requirements and increasingly have to have reclamation plans; oil and gas wells have far less specific requirements (e.g., bonding is not by well but by state or even nation).
  • Mines are a single use of the land; oil and gas production often shares the land with other rural uses.
  • Problem mines are problems for thousands of years–there is no true long term remediation. They can foul a lot of water for a long time. Wells are more insidious, typically failing silently until you know groundwater is compromised or a house blows up.
  • Mines these days are rarely totally shut down; they frequently are mothballed and then brought back online.  Oil and gas wells are frequently plugged and closed.
  • Mining’s main impact seems to be contaminating surface waters.  Oil and gas activity mainly affects subsurface waters.
  • Modern mining remains dominantly rural [save for mining towns!], but oil and gas has moved into suburbia. However, old mines are around a lot of western towns and there is renewed activity (and opposition) from time to time.

So what would the public want for post-development lands? In both cases, one can presume a safe environment available for any subsequent use. In many cases, they might want something resembling the pre-mining landscape. How realistic is this?

For mines, it depends on the mine. Big, modern open pit mines with sulfides are likely nearly hopeless. Strip mines for coal probably can be reclaimed provided they are not in areas where erosion is likely. Many small legacy mines can be shuttered to have an acceptably low level of impact. You can probably tell when a mine can be safely shut down.

For oil and gas wells, there is a surprisingly high level of uncertainty. Modern plugging procedures will usually work for the near term, but if gas continues to migrate up the well bore, any weaknesses that develop in the well plug or around the outside of the well bore will allow the gas to vent to the surface. Degradation of the well materials will connect shallow and deep aquifers, which can be troublesome if the deep aquifers have sufficient pressure to invade a shallower drinking water aquifer.  Or if the deep aquifer has negative pressure, you can lose drinking water to the deeper aquifer. That oil and gas wells are not of the same material as the surrounding rock means that it is likely over long periods of time that some kinds of failures of the well’s plug will occur (chemistry and stress will focus on that interface).  How often is this likely? How often will a failure produce surface problems? We really aren’t certain.

One suggested solution for problem mines is to make use of the waste material. This might help for acid mine drainage, but is less helpful for some other environmental hazards from mines. It is unlikely that a plugged oil or gas well that leaks has any economic utility.

So at the end, what does full closure of mines or wells look like?  Mines are unlikely to have their footprint totally erased, and some will be problems for centuries, but many others will be available for other uses. Oil and gas wells are tougher.  Most rules require a plugged well’s pad to be returned to something looking like the original landscape. When bonding is insufficient (as has been the case in Wyoming, for instance), failed companies’ wells might not be reclaimed. But even where surface reclamation is done (and oil and gas companies like to show pictures of old well sites to show they don’t look particularly bad), the well below is still subject to failure and leaking. While some mine sites might well be safe to build on (and many mountain resort towns are in fact built on old mine sites), building on an old well is playing a bit of Russian roulette. Shallow aquifers could fail as well. Perhaps monitoring for natural gas and pollutants in the water would permit full reoccupation of well sites, but it seems just as likely that rules will prevent building on or too near old well sites.

What do local communities need to know? They should probably understand that oil and gas wells are forever–plugged wells in most cases will cause no problems, but given that we haven’t watched a bunch of wells plugged with modern techniques for a really long time, that there is a non-zero risk of future leakage, and so monitoring appropriate for the subsequent use of the land should be required. Ripping out as much of the oil and gas infrastructure as possible is wise. For mines, it kind of depends. Any mine with underground workings can later collapse, so building on top of such mines should be considered with caution. If a mine is leaking colorful water into streams, odds are this will continue for centuries and some kind of action is desirable, but know there are not, at present, permanent fixes.

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