Geology of the National Parks

Optional Enrichment Article 2


A Bit More on the Marcellus

A Caution

In Pennsylvania, as this is being rewritten (autumn of the year 2017), the Marcellus Shale is the center of a “fracking” industry to extract gas and sell it. Some jobs have been created, and some economic activity. Some people have received money because gas companies paid for the right to extract the gas. Other people who did not own the mineral rights of their land are rather unhappy that the money from the gas on their land is going to someone else.

The issues related to the Marcellus have been contentious for a decade, and it remains virtually impossible to write anything that is not: i) quickly out of date, and ii) likely to make a lot of people mad. But, we cannot ignore the big issues, so here is a little more background.

Some History

The estimates of available fossil fuels that you see in various publications may be very different things. Textbooks often list the total amount that is considered to be available if we continue inventing new technologies and pushing the price slowly higher. This is a fuzzy number—how high can the price go before alternatives are cheaper and we quit trying for fossil fuels? But, this sort of calculation has long assumed that we would go after the gas in the Marcellus and other shales, and the oil in oil shales, and tar sands, and more.

Other numbers on fossil-fuel reserves are much smaller because they count only the nearly-ready-to-pump-out-of-the-ground fuels or some other similar definition. Over the last few years, a lot of gas in the Marcellus and other such black shales has moved from the “available in theory” to “available in practice” column, which has changed a lot of business balance sheets. You will see estimates, often communicated by industry, that the Marcellus and other such deposits contain "100 years of gas," although other estimates (including from the government) have been lower, including 25 years of gas. But, gas is supplying a little over one-quarter of U.S. energy use, so an all-gas system might last 6 to 25 years based on those estimates. That is lots of energy, lots of money, but not even vaguely close to a long-term, sustainable energy solution.

Some Geologic History

When conditions are right, organic materials accumulate in sea-floor muds. Gases dissolve more easily in colder waters (heating a carbonated beverage drives off the fizz). So, when the climate has been hotter in geologic history, there has been a tendency to have less oxygen in the ocean and lakes. Extra fertilizer at the surface may favor the growth of so many plants that the oxygen in the deeper water is used up in “burning” the plants after they die and sink, before the dead plants are used up. Low oxygen in deep water is also favored by restricted ocean basins that prevent vigorous currents to supply newly oxygenated waters. The still conditions of a deep, restricted ocean basin mean that mud isn’t washed away, but that no big chunks such as sand or gravel are washed in. So, an organic-rich mud forms in such places, especially during hot-climate, well-fertilized times.

Eventually, this is a stabilizing feedback on Earth’s climate—when high CO2 makes the climate hot, CO2 is removed from the air by being converted to plants that are buried in these muds. In just a few hundred thousand years, this can make a big difference to how much CO2 is in the air, especially because a hot climate can also remove a good bit of atmospheric CO2 by rock weathering in a few hundred thousand years. Nature thus will remove the CO2 that we are putting up now, and if you have a few hundred thousand years to wait, our CO2 is no big deal. If you care about your great-great-great-great grandchildren, though, these natural processes just aren’t fast enough to help much.

Anyway, the muds in the low-oxygen ocean or lake basins are often black, partly from the organic material, and a lot from having iron sulfide and other black stuff that forms in low-oxygen environments (add oxygen, and the iron in iron sulfide rusts and turns red). As more mud accumulates on top, the black muds get hotter from the heat of the Earth, and the mud slowly is squeezed and recrystallized to make a rock called shale. Shale is the commonest sedimentary rock, and there is a lot of black shale on Earth.

The heating also changes the organic material, making oil and gas. Most oil, and a lot of gas are formed in this way.

However, the spaces between clay particles in the mud/shale are tiny, and even tiny gas molecules and the smallest of oil molecules have trouble moving rapidly through. As more oil and gas are produced, the pressure inside rises (splitting molecules off dead things tends to increase the total volume taken up by the organic materials). Eventually, this opens cracks and allows the oil and gas to leak out. As noted in the main text, most of the leaking oil and gas escape, slowly, to the Earth’s surface, where they are broken down by bacteria or other living things that use the stored chemical energy in the fossil fuels. A little of the leaking oil and gas are trapped in special geologic places on the way, and oil companies have gotten very good at finding those places, drilling into them, and recovering the oil and gas.

Much of the organic material remains in the black shales, though, unable to make its own fractures and escape.

Some Fracking History

Oil companies have been “fracking” for a long time. Suppose that oil and gas leaked from a black shale into one of the special reservoirs that oil companies like to drill into, arriving in just a million years. That is fast compared to many geologic processes, but if it took the oil company another million years to get the oil out of the rock, the oil company would be very unhappy. So, for rocks that allow oil and gas to move slowly, but that contain a lot of oil and gas, the oil companies learned to make fractures that let the fossil fuels move faster.

one of history’s fascinating stories, the actor John Wilkes Booth, before he shot President Lincoln, was an investor in a Pennsylvania oil well. With much of his money committed, and the well yielding slowly, Booth and his co-investors decided to “shoot” the well, exploding gunpowder to fracture the rocks and yield more oil. Instead, they destroyed the well. Now much poorer, Booth switched his focus and soon thereafter shot President Lincoln. But, a new invention, the Roberts Torpedo, from a Union soldier who saw an exploding Confederate shell fracture dirt, soon made shooting wells much safer and more widespread.

Imagine you’re working for the gas company. If you blow up a balloon too vigorously, it breaks. Pump too much air into the bicycle tire, and it may rupture. This is the basis for fracking rocks. Drill a hole to the rocks you want to break. Put in some sort of plug with a tube or pipe going through (so that when you “blow up the balloon” on the other side of the plug, the pressure is pushing against the rock down there and not squirting out of the hole up here). Then, pump water through the pipe into the space below the seal, and pump hard enough that you really raise the pressure, “break the balloon” by cracking or fracturing the rocks. Release the pressure, and oil and gas can leak out of the new cracks to your hole, and up the hole to the surface, perhaps aided by a well pump that you use. (Companies that generate geothermal power also may “frack” to make spaces for hot water to move easily.)

Notice, though, that if you pry open a crack, and then quit prying, nature may squeeze it back closed. But, if you put some sand in below the plug, when the rocks break, the sand can squirt into the cracks and keep them from closing. A crack that is twice as wide carries eight times more fluid, all else equal, so this can make a big difference.

In addition to the sand, you might add something to keep microbes from growing in your new cracks, eating your valuable methane and clogging the cracks with dead-bug “gunk.” And, you might want to add some surfactants. For example, many antacids include a chemical (simethicone) that reduces surface tension so that small bubbles in the stomach can combine into larger ones that can be moved along more easily; chemicals to do the same job may be added to fracking fluids, for the same reason. You might even think of other things to add.

Once you have this fluid, some of it will stay in the cracks you make. And, the fracking is generally way down, so it is very unlikely that the cracks will reach all the way to the surface, or to the shallow level of water wells. But, some of the fracking fluids must come back up the hole to get out of the way so your gas can come out. You may recycle this “flowback,” or dump it in the creek or at the sewage treatment plant, or pump it into even deeper wells somewhere just to get it out of the way. Deep disposal and recycling have largely replaced earlier techniques. But, in Oklahoma and elsewhere, when some of this fluid was pumped into deep wells, it seems to have triggered earthquakes. (The quakes happened where and when the pumping was going on, not huge quakes but big enough to crack plaster and otherwise damage houses.)

A gas well used in fracking must be drilled through shallow and intermediate depths on the way to the shale to be fracked. The plan is to seal the well so that there are no leaks of gas or other fluids into those shallow and intermediate depths where people may have water wells. But, if the sealing isn’t done properly, it could leak. Leaks of that sort from gas and oil wells have been reported, but there aren’t a lot of public data on just how often, and just how large the leaks are. The mix of chemicals may be a trade secret, so people worry may not even know exactly what is there to leak.

Some Global-Warming Considerations

Regardless of what your politician or pundit may have said, the science really does give us high confidence that a long-term shift away from fossil fuels is economically beneficial to avoid the damages of changing climate. Natural gas produces more energy from the same number of carbon molecules than coal (or oil from tar sands), so if natural gas is used in place of coal, this can reduce warming. However, if natural gas is used in addition to coal, then it increases warming.

And, there is a qualification. If you let natural gas (which is almost entirely methane) leak into the air without burning it, the methane is a greenhouse gas. Per molecule at current levels, methane causes more warming than CO2, and after a decade or so the methane is oxidized to CO2 and then stays up typically for additional centuries. So, if natural-gas production is too leaky, that may be even worse than coal in terms of causing warming; leakage also wastes money for the gas companies.

A Bit on Policy

In Pennsylvania over the last few years, the public discussion included everything above, but especially focused on jobs and the economy and taxation. Every major gas-producing state in the US except Pennsylvania had taxes or fees that provided notable funds to the public coffers, with Pennsylvania having only a relatively quite small local impact fee. Those who favored the no-taxes approach in Pennsylvania typically have argued that taxes might drive away the gas companies. Supporters of taxing have often noted that no gas company would be stupid enough to come into Pennsylvania assuming the no-tax position was guaranteed for the long term. The companies can look across the nation, see that every gas-producing state except Pennsylvania had levied taxes, and that Pennsylvania had budget problems that could be eased by levying taxes, and it seems reasonable that a planner for a company would run the numbers assuming that Pennsylvania would follow all the other states.

However, once a company decided to enter the state, a good business person would note that production achieved before any taxes were levied would be more valuable. This might justify hiring more workers and otherwise working faster, which would stimulate the economy but provide less long-term stability. It also might justify cutting some corners, allowing more leakage or otherwise adopting less-efficient but faster approaches. Reliable studies balancing these issues have been lagging behind the pace of development.

A Resource Curse?

Lurking behind all of this discussion is something that economists argue about a lot, called the “Resource Curse.” With certain notable exceptions, countries that rely heavily on the extraction of concentrated valuable resources (diamonds or oil, for example) have often had less economic growth than might be expected based on the size of the economic input from the resource, and many residents of western democracies do not like the social conditions in such resource-producing states. (You can think of the leading oil exporters in recent years, including Saudi Arabia, Russia, Norway, Iran, United Arab Emirates, Venezuela, Kuwait, Nigeria, and Algeria, and decide whether this “academic” view of the resource-reliant economies seems accurate, nearly accurate with maybe a few exceptions, or really wrong.) Mere production of fossil fuel is not seen as an economically bad thing by the economists who have recognized the resource curse; the worry is attached to reliance on the money from the valuable resource (the US is a major oil producer, but oil production is not a dominant part of our economy). There are many ideas on why the resource curse exists (and a few experts who still deny that it exists); perhaps the most common idea is that if people put effort into controlling the temporary resource rather than building a sustainable society, they end up with a poorer place to live.

The observation of the author is that there has been rather little public discussion in Pennsylvania on whether reliance on a soon-to-be-depleted natural resource is the best way forward for the Commonwealth.

The author will also state that he isn’t coming out for or against Marcellus Shale gas development, that it may ultimately turn out to be more “good” than “bad,” or the other way around. Furthermore, even if the author did take a side, almost no one would care. The development has been going fast, many people love it, and many people don’t.