Extracting Oil and Natural Gas

[Dekan]

For over a century, we have been drilling into the Earth. In order to suck up oil and gas.

 

This oil and gas was underground for millions of years. During those years, it must have played some part, in supporting the ground above it - ie, the surface.

 

When we remove the oil and gas, by pumping it up, aren't we removing the surface's support - so risking a collapse?

 

Collapses occur, in the case of land on top of abandoned coal mines. The mineshafts, made hollow by removal of coal, are only kept up by wooden pit-props. These props eventually decay. Then the mineshafts collapse. Which causes the land above to subside. This subsidence affects houses and property built directly on top of old coal mines - ie, it's fairly localised.

 

But the mining of oil and natural gas, is not localised. It's taking place on a huge, planet-wide scale. Trillions of cubic meters of gas and oil, extracted from entire continents, and oceans. Evacuated wholesale from the rocky strata which underpin the surface all over the Earth!

 

Won't this lead to a weakening of the Earth's crust - with consequent global surface subsidences?

[Joatmon]

Extracting shale gas reserves under Blackpool UK has been blamed for two minor earthquakes.

 

http://www.independent.co.uk/news/science/small-earthquake-in-blackpool-major-shock-for-uks-energy-policy-2291597.html

Edited April 7, 2012 by Joatmon

[Arete]

Oil and gas reserves are by and large found within porous rocks. Extracting the oil/gas does not generally create an underground void.

 

http://en.wikipedia.org/wiki/Oil_reservoir

[Dekan]

Thanks Joatmon and Arete, for your kind replies.

 

The Blackpool business, shows what can occur - though it was apparently due to pumping stuff down into the Earth.

 

It's the bringing up of stuff, that gives most concern. We are continually raising huge masses of oil and gas from under the surface. This material, once up, must press heavily on the surface. True, some gets burned, and released as gas into the atmosphere - but this only produces a similar weighty effect, as the atmosphere presses down on the surface.

 

Won't this increasing pressure eventually produce catastrophic results - in the form of Global Subsidence?

 

I ask this, because Global Warming seems slightly discredited these days. Even though it's now got a new name -"Climate Change", that hasn't stopped attacks from the infidel Sceptics and Denyers. Don't these people realise that we need something to worry about?

 

So as a replacement worry, I modestly propose Global Subsidence.

[Suxamethonium]

I'm not an (atmospherologist?) so please correct me if I am misguided, but I would feel that the 'added mass' contributed to the atmosphere would not be cause for major concern for the following reasons:

 

*The light gases from such drilling (e.g. helium, hydrogen) escape the earths gravity over time and as such their mass will not accumulate over time.

*Carbon dioxide resulting from combustion of the mined products will quickly integrate into the natural systems ultimately leading to a significant amount entering the oceans and eventually precipitating as carbonate rock on the sea floor. A similar process would likely occur for the sulfurous products via atmospheric hydrogen sulfide.

*Of any gas that was to remain in the atmosphere, its weight would be roughly evenly spread over the whole surface area of the earth. It would also take up volume, potentially pushing more gases into the exosphere to slowly dissipate into space removing mass from the atmosphere.

 

As for the 'voids' I haven't really got any ideas.

[Ophiolite]

As previously noted, the exploited hydrocarbon reserves are found in porous and permeable rocks, typically sandstones and carbonates. Pore space typically constitutes between 5% and 20% of the rock.

 

When the hydrocarbons are extracted three things tend to occur - the pressure in the reservoir falls and the remaining fluids expand to fill the potential void; fluids move into the reservoir from adjacent formations; the reservoir rock may undergo some compression.

 

The extent of the latter process will depend upon the amount of fluid withdrawn, the efficiency of the first two mechanisms and the character of the reservoir rock. Fine grained, well sorted, rounded, siliceously cemented sandstones will show little tendency to compression; chalks and loosely aggreagted sands the most. The Ekosfisk field in the Norwegian sector of the North Sea was the first commercially exploited North Sea oil, production beginning in the 1960s. By the 1990s subsidence of the seabeds amounted to several metres. New production platforms were installed and the main platform raised a corresponding amount.

[JustinW]

I would also like to bold what Ophiolite said because I think it bears repeating for those who wish to ignore it.

 

As previously noted, the exploited hydrocarbon reserves are found in porous and permeable rocks, typically sandstones and carbonates. Pore space typically constitutes between 5% and 20% of the rock.

Typically found in shale deposits where I'm located. Has anyone ever held shale and felt how brittal it is? It's hardly a structural material. This is why the pumping of sands and water into a hole are able to crack a fissure wider to allow the gas to seep through.

 

 

 

The one thought I have had about this didn't include subsidence but rather a mixing of water supplies. Not that that would even have much of an impact on anything, but some have noticed that the minerals found in our water table are changing in different places once gas wells locate in the area. One person I talked to just last week said he noticed sulfur in his water. Which is quite common for the area about 10-15 miles away, just not in that particular area until recently. I wonder what possible impact it would have if it was causing water supplies to mix? Just a thought.

[zapatos]

Edited April 10, 2012 by zapatos

[JustinW]

Yeah I've heard that was happening too. Although not in my kneck of the woods yet. It definitely gives you something to think about and wonder how to go about fixing some of the possible problems that can come about as a result of frac-ing.

[Suxamethonium]

I was under the impression that fracking would only cause that effect in houses which use bore/ground water.

 

I guess I got that impression because the gas is coming out of solution at atmospheric pressure, so water that was originally sitting in a dam or processed by a plant would quickly degas. Would be interested if anyone can verify that though as it is only my own conclusion.

[Silica]

This is a very interesting article by, Julian Bulman, and it explains several aspects of the fracking non-debate.

 

It is reproduced with his permission.

 

Human ingenuity and technological advances have given us the ability to interact with our environment as no other animal or plant has been able to do through the whole of our planets 4.54 billion year evolution in such a small and inconsequential geological timescale. This includes the ability to produce significant earthquakes and other seismic activities using these technological advancements.

 

As we have developed our technical abilities we have also inadvertently caused earthquakes and other seismic events. The simplest example of this is our conventional and nuclear weapons capability where various conventional explosions and nuclear tests have registered on the ML scale (Richter Scale).Going so far as to produce upwards of magnitude 5 quakes for some underground nuclear tests in the late 1950's and also possibly leading to further quakes in otherwise quiet seismic areas.

 

However weapons are not the only way humans have induced earthquakes and other seismic events.These other inducements include fluid injection into the earth technologies,large earthworks and dam projects, mining and geothermal technologies. Here are several examples of how these technologies interact with seismicity:

 

Reservoirs- The mass of water in a reservoir alters the pressure in the rock below and through fissures in the rocks, lubricates the faults on which they may sit, which can trigger earthquakes (possibly extremely large magnitude quakes).Reservoir-induced seismic events can be relatively large compared to other forms of induced seismicity.

 

The first case of reservoir induced seismicity occurred in 1932 in Algeria's Oued Fodda Dam. There have been similar incidents including the 6.3 magnitude 1967 Koynanagar Earthquake attributed to the Koyna Dam reservoir. During early construction of the Vajont Dam in Italy, there were seismic shocks recorded during its initial fill. After a landslide almost certainly triggered by this increased seismicity filled the reservoir in 1963, the local tsunami in the lake behind the dam caused by the landslide over topped the dam causing a massive 250m high megatsunami and subsequent flooding with around 2,000 deaths, it was drained and consequently seismic activity has become almost completely non-existent. On August 1, 1975, a magnitude 6.1 earthquake at Oroville,California, was attributed to seismicity from a massive earth-fill dam and reservoir recently constructed and filled there. In Zambia, Kariba Lake may have provoked similar effects.

 

More recently, the 2008 Sichuan earthquake, which caused approximately 68,000 deaths, is another possible example of a large dam project inducing seismicity. An article in Science suggested that the construction and filling of the Zipingpu Dam may have triggered the earthquake. However, researchers have been denied access to seismological and geological data to examine the cause of the quake further. Some experts worry that because of this apparent link with the 2008 Sichuan event the Three Gorges Dam in China may cause an increase in the frequency and intensity of earthquakes.

 

Mining - Mining leaves voids that generally alter the balance of forces in the rock. These voids may collapse producing seismic waves and in some cases reactivate existing faults causing minor or even large earthquakes. Natural cavern collapses that form sinkholes would produce an essentially identical local seismic event. We have also been responsible for several volcanic inducements by drilling into seismically active areas such as the Sidoarjo mud flow in Porong, Sidoarjo in East Java,Indonesia, which was caused by the company PT Lapindo Brantas sinking a natural gas well and then over pressurising the system by fracking (see below).

 

Geothermal energy - Enhanced geothermal systems (EGS), a new type of geothermal power technologies that do not require natural convective hydrothermal resources, are known to be associated with induced seismicity. EGS involves pumping fluids at pressure to enhance or create permeability through the use of hydraulic fracturing techniques. Induced seismicity in Basel led to suspension of its HDR project. A seismic hazard evaluation was then conducted, which resulted in the total cancellation of the project in December 2009.

 

HydraulicFracturing -This is particularly pertinent at the current time with the non-debate (scientifically at least) over fracking technologies in the United States (no it's not a swearword from Battlestar Galactica).

 

Hydraulic fracturing, to give fracking its correct term, is a technology used to induce or propagate fractures in rocks by injecting pressurised fluids into those fractures and thereby releasing held oil or gas allowing those fossil fuels to migrate either to existing reservoirs or to come directly to the surface. For simplicity, using fracking technologies, we are rapidly increasing and decreasing the pressure on natural faults within the earth's crust to release hydrocarbons and actually lubricating and extending these natural fracture zones. Anyone therefore who cannot see the link between increased seismicity and fracking is not only delusional but does not understand the basic premise that fracking is all about creating minor earthquakes to release the held hydrocarbons.

 

If you listened to opinion and editorial nonsense from the media you would assume that fracking is a safe, wholesome technology that is helping America become less dependent on foreign oil so three cheers for the good ol' US of A. Unfortunately this is not the case and factual studies have proved beyond a shadow of a doubt that these fracking technologies can and have produced substantial earthquakes and increase seismicity wherever the technology is used.

 

As a more pertinent warning; there are many fracking techniques currently being undertaken close by or actually on the New Madrid Rift faulting system and, due to not understanding how that fault zone may be activated, we could conceivably activate and therefore induce a magnitude 8 + earthquake in the region.

 

That is why it is vitally important that any person understands that opinion is not fact. To cut to the chase any media source that promotes fracking as a safe technology are lying to the general public and are part of the scams and frauds perpetrated by business interests that could and will likely lead to an extreme event in more seismically active areas of the continental US.

 

Fracking causes seismic activity as the pressures are released, this is a fact backed up by years of research and evidential support. Fracking also causes many other potential environmental impacts including; contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface, surface contamination from spills and flowback and the various health effects of these. For these reasons hydraulic fracturing has come under scrutiny internationally, with some countries suspending or even outright banning its use.

 

That is not the case in the United States and for exactly the same reasons that there is a non-debate on human induced climate change between scientists but public opion seems to think there is. Namely this is because corporate America (and all large global producers affecting the environment) have far more money to spend on disinformation campaigns than scientists have on promoting their real and proven, and therefore, factual research.

 

Thus these corporates spend huge amounts of cash seeding junk science, disinformation campaigns, pressure groups and opinion to the mass media and this directly affects the vast majority of people's views and opinions who believe that scientists are debating whether Human Induced Climate Change or Human Induced Seismicity is actually a real thing. The reality is far different.

 

To put it bluntly 97% of scientists agree that the earth has been heating up over the last 300 years due to the proliferation of carbon we humans have been putting in to our atmosphere with a particularly strong spike in the last 50 years or so. The other 3% of scientists, who are either on the fence or against these theories, are likely to be either financially supported by big business or are dependent on them in some way for funding (it pains me to say that most scientific dissenters are geologists who rely on the energy companies for work).

 

This is the same for Human Induced Seismicity, seismographs are impossible to fake so any earthquakes that are in the vicinity of these various fracking technologies a link can be made using evidence support systems which is why there is no debate in the scientific community about fracking causing earthquakes, the science is proven and the earthquakes caused cannot be faked, especially in areas with little to no known previous seismic activity.

 

My advice is to not listen to opinion but to seek out the actual scientific studies for yourselves, if you don't understand them listen to someone that does like a scientist and not a journalist, politician, religious leader or someone else in the pay of big business or who has something to gain by being a denier.

 

Remember opinions are not facts. 'Nullius in Verba' ("Take nobody's word for it") the motto of the Royal Society.

[CaptainPanic]

It is quite common in the north of the Netherlands to have minor earthquakes, and these are directly linked to the extraction of natural gas.

 

I think this website, from our national meteorological institute (KNMI) is the most comprehensive:

The catalogue of earthquakes induced by gas production in the north of the Netherlands contains 688 events to date (Feb 2011).

 

It should be noted that no earthquake of >4 on the Richter scale has occurred. All quakes were minor, with only minor structural damage - often no damage at all.