OK, so I will get into the fray, even if I already know I will regret it...
Full disclosure: I have been working for the biggest service company in the oil and gas exploration industry (hi Max!) for 27 years. Our clients are the Chevron and BP and Aramco of the world, which sub-contract most of the work to companies like the one I work for and its competitors. And, yes, that includes fracturing (aka fracking); a service I am much familiar with; I have been working most of my career in an organization that design and build equipment (and chemistry, but I am not a chemist) for fracturing services.
WARNING: I already know that by the time I am done, it will be a FUCKING LONG POST, so if you have the attention span of a shrimp, don't even bother.
I will try below to give first a few basis statement on the oil industry and the fracturing business. I will then try to give a simple didactic (some may say pedantic) explanation of what is truly fracturing, and conclude with the risks associated with fracturing and what can be done to alleviate those risks.
So a few facts, confirmation and/or infirmation of a few things said in previous posts:
1) Trump is wrong: yes global warming is real. yes it is man-made and yes it is mostly (but not only) linked to the use of hydrocarbon as a source of energy.
2) Today, about 3/4 of energy production in the world is carbon-based (coal, oil, gas)
3) If you are one of the screaming, foaming-at-the-mouth righteous people lashing out at the oil & gas industry (yes, I am talking about you, Ed), there are only 3 options:
- you live like your great-grand parents, prior to WW I
- you are at the bottom of the socio-economic ladder in a third world country
- you are a hypocrite
If you do not agree with this, read again statement 2)
4) Oil & gas will eventually have to go away, but it is still too much of the energy mix to just shut it off and not bring the world as we know it to an end right away. That being said, if we do not do something, it will be the end of the world as we know it pretty darn fast anyway. So even though I work in the oil and gas industry, I fully understand (and agree!) that the sooner we get out of it, the better.
Now please allow me to give a (pedantic) explanation of the oil & gas and fracturing business, and the risks associated with it. Consider it a "101 primer" on the topic. OK, looking at the length of the post, it is 101, 102 and 103 combined...
Hydrocarbon are the results of a veeeerrrrryyyyy slow chemical transformation (we are talking of geological time frame, here) of "former living matter" under very high pressure and very high temperature. Hydrocarbon may migrate from the "mother rock" where it was formed to another geological formation where we find it today. How can that happen? There are 2 key characteristics that explain it: the rock porosity and permeability.
Porosity represent the amount of space in the rock that is not occupied... by rock. Oil or gas takes that "free" space in the rock. Big common mistake: we are NOT talking about caves full of oil or gas!!! But instead of a multitude of microscopic voids throughout the rock. So the higher the porosity of the rock, the more hydrocarbon it can hold.
Permeability is the capability for a fluid to "flow" through the rock because of a difference in pressure in different zones.
Caution: porosity and permeability are not necessarily correlated; you can have a rock with many microscopic holes, but they do not communicate well with each other (high porosity, but low permeability). You can have a rock with virtually no voids, but with natural cracks (low porosity, but high permeability).
So if motion of the fluid in the rock is possible (there is some permeability), the fluid will migrate from a high pressure zone to a lower pressure zone nearby; usually higher, as obviously, the closer to the surface, the less pressure in the rock.
Why is it important? Because if we find oil in a specific rock formation, it means that it has an impermeable layer of a different rock above it. If it did not, it would have continued to migrate upward until it found a barrier. When there is no impermeable barrier above, it migrates eventually all the way to the surface and it ends up as a seepage of oil, at surface, as it is found in a few places around the world.
So there is a natural impermeable rock barrier above the hydrocarbon deposit that isolates it from the upper rock formations, where resides fresh water.
So when we drill a well through the rock formation bearing oil, the pressure inside the well is so low (only hydrostatic pressure) compared to formation pressure that the fluid in the rock porosity tends to migrate toward the well, rushing to surface once inside the well. But if the permeability of the rock is low, the fluid has a hard time to migrate to the well; in other words, the well will be able to draw only from a short radius around the wellbore. To avoid that, either you drill a myriad of vertical wells close to each other so you leave no area untapped (old method), or you drill vertical wells and you "frac" them (conventional method) (I will come back on how we do fracturing), or you drill horizontal wells and you perform multiple frac jobs on the horizontal section of the well (what is call in the industry "unconventional", the method behind the current boom of production in the US).
Why horizontal wells? Some of the target area for a well may be only 50 ft thick, but 8000 ft below surface. So to get to the "pay zone", you have to drill through 8000 ft of rock which has no interest to you, then the next 50 ft is what you are after, and drilling further down will not provide any more oil production... This is a lot of "wasted" drilling for a very thin area of interest. If you want to improve the ratio pay-zone length vs. total drilled length for a well, you start vertical and a few hundred feet before you reach the pay zone, you start veering the drilling direction to go from vertical to horizontal. If you calculated and monitored the drilling correctly, you end up drilling horizontally smack in the middle of that 50 ft thick zone you were targetting; as you extend the horizontal drilling section of the well, what was only a 50 ft "poking-through" pay zone in a vertical well can now be a several hundred feet of direct contact with the pay zone, if you can continue drilling horizontally in that oil loaded rock formation. And YES, we can do that; it is called directional drilling. We can "steer" the drillbit to go more to the left, more to the right, more vertical, more horizontal... and measure at the same time to characteristics of the rock, to make sure that we stay in the zone of interest. (but this is more like the 501 or 601 course...)
But even with horizontal drilling, in a very "tight" formation (low permeability), you can draw hydrocarbon only from the direct vicinity of the well. This is where fracturing will multiply the performance of the well.
So what is a fracturing operation, really?
So first of all, NO it does NOT "consists of shocking the sediment with a shot of sand and water to loosen the sediment". In a fracturing operation. you pump fluid (followed by fluid loaded with sand called "proppant") at such a high rate and pressure in a specific section of the well that the formation cannot take the rate of fluid coming in only as seepage into the rock: you actually fracture the rock (this is why I prefer to call if fracturing, rather than "fracking"), the fluid rushes to fill that fracture and as you continue pumping very fast, you propagate the fracture further into the formation. The shape of the fracture is like 2 vertical elephant ears, on each side of the wellbore. It is only a fraction of an inch thick, but can be a few dozen feet high and reach several hundred feet horizontally away from the wellbore.
If we pumped only fluid, once we stop pumping and release the pressure at surface, the fracture that we just created would simply collapse on itself and close. To avoid that, we add sieved sand (all grains of same size) to the fluid, so when we stop pumping and release pressure at surface, the sand "prop" the fracture open, therefore the name of proppant... That fracture is now filled with compacted sand, which has a MUCH higher permeability than the rock; it is a "highway to the wellbore" for the oil or gas trapped in the rock. Imagine a droplet of oil that was 100 ft from the wellbore; without fracture, it would have to travel 100 ft through rock to reach directly the wellbore and be produced to surface; that may never happen because of too low rock permeability. Now that the fracture has been performed, that elephant ear of a fracture may be only 15 ft away from that same droplet of oil. Now it only has to travel 15 ft across rock to get to the fracture, and then zoom to the wellbore (very high permeability through the sand in the fracture) and then travel up the well to surface.
Why the Shale formation boom? (see post 126 to see what formations we are talking about).
Those Shale Gas and Shale Oil zones (or "Play" as it is called) were well known for a long time, but is was not economically feasible to produce them. Several factors changed that:
- first of all a sustained high price for gas and oil (the OPEC producers got too greedy for too long) re-ignited interest in those zones
- new production techniques, much cheaper that made those zones economically viable. The first part is the architecture of the wells I described above. Horizontal wells, with many fractures, one after the other on the horizontal section of the well.
- the last technical revolution is the chemistry of the fracturing fluid we pumped... OR LACK THEREOF !
In conventional fracturing operations (vertical well with ONE frac job), we used to pump very complex (and expensive) chemistry: we put high concentration of proppant (sand) in the fluid. We woud add long molecule polymer additive, cross-linker additives, breaker additive, etc. They would react at different time of the operation to achieve different fracturing fluid viscosities throughout the operation. Some of that stuff was (and still is) nasty.
But for Shale formations, with some trial and error, some more research, the industry came up with a very simple (and cheap) chemistry and mode of operation: put just a bit of simple polymer, no cross-linker, no breaker and add sand. And that's pretty much it. The polymer is used as a "friction reducer", it is here to make the viscosity just right so you can pump very fast in skinny long well, without generating too much friction losses. If you pump that stuff fast enough, proppant will stay suspended and be carried out into the fracture. In the industry jargon, we call this type of chemistry "slick water".
That polymer is most of the time a derivative of guar. It is a plant originally from India, that gives a natural polymer that is used as a gelling agent in different industries, including cosmetics and food industry.
So YES, some of the chemistry we pump in conventional operations is nasty, but the development of unconventional wells with "slick water" chemistry actually simplified the chemistry and somewhat reduced the use of some of the worse chemicals.
On the other hand, the amount of fluid used is just MASSIVE. For ONE fracture, it is not uncommon to pump at about 40,000 gpm, at 12,000 psi (that's 300 times the pressure in your car tires...) for one to two hours; each horizontal well will have up to 30 zones to frac, each well site will have 6 to 10 wells side by side. A frac crew will pump 12 to 16 hours per day, 7 days a week, for up to 6 weeks on the same "pad". There are most likely through the industry several hundred of crews in operation any single day, in the US.
Now saying that we need to simply stop fracturing is PURE LUNACY. A geologist once explained to me that the shale formations that are at the core of the current production boom have a permeability similar to concrete. Nothing viable will come out of those formations without fracturing. And this is about 50% of current US production.
And most (if not all) of the rest of the US production do need fracturing as well anyway!!! American oil and gas formation have been in production long enough that the good old day where you just open the tap and oil flows freely are long gone. The easy stuff is already out of the ground...
So can fresh water be contaminated?
You remember that I said that there had to be a layer of impermeable rock above the oil or gas zone to trap it... but at the same time, the well has to poke through all zones and potentially put in intercommunication all the different layers of rock.
The construction of the well, as it is drilled is supposed to ensure good zonal isolation. When we drill a portion of the well, we then stop, and lower inside the well all the way to the bottom, sections of a tube of steel, each section being screwed to the one below. This is called the casing. Then we pump cement slurry in the small gap between the casing and the rock formation. If this is done correctly, the zone that has been just drilled has been sealed off again. Once we have finished the drilling and casing installation and cementing, we perforate the casing in the specific areas that we want to produce from. It is through those perforations that we pump the fracturing fluid into the rock and that eventually oil or gas will enter the well.
Fracturing operations are not going to "burst" the casing as I have read above, but if the cement job that bonded that casing to the rock behind it is not well done, there could be communication, behind the casing, between different zones. hydrocarbon could migrate behind the casing, from the production zone, all the way to the fresh water zone, and because of the pressure difference, re-enter the rock in that area.
There are rules, standards and regulations on what a good cementing operation that bonds properly the casing to the formation should be and should achieve. If those rules are followed properly, there is no reason to have communication behind the casing from the "pay zone" to any other rock section above...
FINALLY, some people refered to "produced water" that is loaded with nasty chemicals.
First of all, you need to know that the "oil companies" is a misnomer. They shoud be called the "water companies" or the "brine companies". A very large portion of the fluid produced by the wells is not oil or gas, but water. Part of it is what is injected into the well during the fracturing operation, that comes back to surface once you put the well in production. And that water will carry back to surface not only what was added for the fracturing operation, but also what it has picked up from the rocks down below... And yes, it can be nasty stuff that needs to be treated.
More and more often, the clients ask us to re-use some of that water as base fluid for the next fracturing operation. Even if the chemistry of the "slick water" jobs is simple, there is a point where the chemistry does not work anymore with the chemical elements brought back from the formation.
Yes, the industry has to improve, especially in its water usage and production. Service companies like the one I am working for, are trying to develop new techniques to reduce the total amount of fluid pumped to achieve a given size of fracture.
Yes it also has to ensure proper zonal isolation so nothing migrate through the annulus to a higher zone or even to surface. The regulations on the cementing techniques must be applied/enforced and potentially improved.
But what is the alternative TODAY? Really?
Go back to coal? Global warming impact is worse. Truly, natural gas is the less bad of the current options.
Stop US Oil production? Is the US willing to become fully dependent of foreign countries on energy? Or are the american people ready to go back to 19th century lifestyle? I don't think so...
One of the area of improvement that has not been talked about is ENERGY CONSERVATION. Not demanding more fuel efficient transportation is insane. The building code in the US is insane. I don't think that there has been one house built in France (my home country) in the last quarter century without double pane windows, because it is mandated by the regulations...
All of those steps are only transition solution, I know that, but until we find a better technology (or portfolio of technologies) for our energy, we have to find ways to soften the blow...
PS: if you are one of the 3 people who will read the wole thing, thank you!
PPS: I think I broke a record for the longest post EVER!