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Hi! My AP Environmental Science class is in the midst of learning about renewable & nonrenewable resources. We are also talking about oil drilling in Santa Barbara County.We are wondering what the main difference is between fracking and cyclic steaming. What are the pros and cons involved with each and what types of drilling is best for our environment.We look forward to hearing from you. We are hoping to get some different perspectives on this--like from geologists, biologists, chemists & environmentalists. Thanks! Laura :)
Question Date: 2014-04-11
Answer 1:

I really like this question! (I’m a geologist, so you know, because you were interested in different frames of reference) There are three basic ideas that people need to know to understand these two techniques.

The first is porosity. Porosity is the amount of open space in a rock. Rocks like granite, where crystals have grown together have almost no porosity, but rocks like sandstone have high porosity (20-30% of the rock), because the sand grains don’t fit together perfectly. The pores in a rock are where ground water, oil, and gas exist.

The second idea is permeability. This is how well water, oil, and gas can flow through a rock. Sandstones are rocks with high porosity and high permeability. This means that they can hold a lot of water, oil, and gas, and those fluids can flow through the rock, so they are easy to get out. “Shales” are rocks made mostly of mud. These rocks can have high porosity like sandstones, but usually their permeability is very low, meaning the fluids are “trapped” and cannot flow out of the rock.

The third idea is viscosity. When we are talking casually, we usually just say “oil and gas.” In reality though, there are dozens of different hydrocarbon molecules (chains of hydrogen and carbon), especially in “crude oil.” Longer, heavier hydrocarbon chains are more viscous, meaning they flow more slowly.

Since we have been extracting oil and gas for over 100 years, we have already extracted most of the “easy stuff.” This is where fracking and steam cycling come in.

“Fracking,” which is short for “hydraulic fracturing,” is when water (with a bunch of additives) is pumped into the ground at high pressures in order to break the rock apart. More fractures mean that the rock is more permeable and so more oil and gas can flow to the well and be extracted. With shales and sandstones that aren’t permeable, this is the only way to get oil and gas out, but it is also used to increase the productivity in areas that are already producing.

Cyclic steaming is used to extract the heavy hydrocarbons that don’t flow easily. The main goal of injecting steam is to heat up the oil, because hot oil flows faster and they can extract hydrocarbons that would otherwise flow too slowly to be economically viable. The viscosity analogy that people often make is honey or molasses. They flow very slowly when they are cold, but if you heat them up they will flow much faster.

Answer 2:

Hydraulic fracturing (fracking) and cyclic steaming are both designed to make it easier to extract oil that is stuck in pore spaces in the rock in which the oil is trapped. However, they are aimed at slightly different reservoir/oil types. Cyclic steaming is often used when the oil is what they call 'heavy' oil. This is a type of oil that is very viscous (resistant to flow) and sticky, almost like tar. The oil's viscosity decreases as its temperature goes up, allowing it to be recovered. So with cyclic steaming, the production company drills a well into an oil reservoir and injects steam into the rock until the little tendrils of steam are able to heat up and 'liquify' the otherwise immobile oil. Then the injector well is converted back into a producer well, so that all the warm, runny oil can be brought to the surface. The well is then turned back into an injector well, and so on, until the reservoir has been effectively depleted. This type of oil recovery is sometimes called the 'huff and puff' method.

Cyclic steaming is usually used on sandstone oil reservoirs, which allow fluids to flow relatively well (as long as the fluids are not too viscous!)

Hydraulic Fracturing is often used when the oil reservoir is very impermeable (meaning the pore spaces in which the oil resides are not connected, and thus the oil cannot flow to the production well). In these rocks, the oil need not be heavy, but the impermeability of the rock is what limits its ability to flow. In these cases, the production company drills a well into the oil reservoir, then pumps a large volume of dense fracking fluid and sand into the well under extremely high pressure. This pressure creates a network of fractures in the oil reservoir that increase its permeability, allowing the trapped oil to flow back into the well. Fracking is most common on reservoirs made of shale, which do not allow fluids to flow very well.

Both methods involve using fluids to 'stimulate' the well into production. However fracking involves actually breaking the rocks to release the oil, while cyclic steaming involves heating the oil up so that it can flow. So, it is rare for both methods to be applicable to the same oil field.

Both methods are carried out carefully, so that only the rock interval containing the oil will be affected by the fracking fluids or the steam. Usually a regulatory agency monitors the drilling of the well and the fracking/steaming process to make sure the injected fluids are going where they should be going. However, not every well is perfect and sometimes wells have to be shut down for leaking steam or fracking fluid into the wrong rock layers. Both methods are also very energy-intensive. In order to generate enough steam to heat up an oil body, an enormous amount of natural gas is burnt...so we end up using a lot of energy to create energy. Also, the water that gets converted to steam must come from somewhere. Steaming means a lot of water comes up with the oil, and that contaminated water must be re-injected into the reservoir to dispose of it. Not a very efficient way to make oil, so the only reason it works is because the price of oil is so high! When the price drops, cyclic steaming will slow down considerably.

Fracking requires a larger initial investment, but is likely to be more efficient over the long run (as long as the geologists and engineers have done their homework!)

Hope that helps,

Answer 3:

This problem is complicated because your question is really an engineering geology question, which means that I, despite being a geologist (specifically, a paleontologist), do not really understand the differences between them well enough to answer your question. Both involve breaking up rock and then inputting something to prevent subsidence after extraction, but the environmental consequences of each are going to vary depending on the circumstances, whether it's on land or in the ocean, and possibly on the character of the oil reservoir as well.

It also depends a great deal on the quality of the engineering; drilling for oil is only very locally destructive from an ecological standpoint, unless something goes horribly wrong and you get an oil spill. Getting an oil spill of course is something that nobody wants, the oil companies least of all (ethical reasons aside, they're losing all of that valuable oil). I'll note that it's been several decades since the last oil spill in the Santa Barbara channel, which at least suggests that the quality of the engineering is fairly safe. That said, drilling oil is going to have global environmental effects as well, in the form of greenhouse emissions.

However, again, not being an engineering geologist or a marine biologist who studies the effect of oil drilling, I can't really comment on which is better and why, especially in this specific instance.

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