How is it possible that gas is stored kilometers deep? Where does all the material on top come from? If new plankton would create more gas, would the new gas be at similar depth in a few 100 million years? And would current reserves be even deeper in billions of years, perhaps 10s or 100s of km deep?
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1$\begingroup$ Quoting Freeman Dyson: "The three things were calcium carbonate which is sedimentary rock, iron oxide which is a component of igneous rock, and water. These three things are certainly present when a slab of subducted ocean floor descends from a deep ocean trench into the mantle. The experiment showed that they react quickly to produce lots of methane, which is natural gas." $\endgroup$– Rodrigo de AzevedoCommented Oct 17, 2022 at 13:17
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$\begingroup$ @RodrigodeAzevedo interesting theory but those 3 things don't have any H atoms in there chemical composition so how this create methane. I don't know. Other planets would have atmospheres made of methane and we probably would never lived on earth as the methane escaping would have polluted our atmosphere already billion of years ago. $\endgroup$– WouterCommented Oct 17, 2022 at 14:59
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$\begingroup$ @rodrigodeAzevedo I think Freeman Dyson should have mentioned that in this sedimentary rock there is about 1 to 2 % organic matter which produced gas not the rock itself as he suggest. (planete-energies.com/en/medias/close/…) $\endgroup$– WouterCommented Oct 18, 2022 at 23:22
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$\begingroup$ He suggested? An experiment was conducted and Thomas Gold's hypothesis was validated. Yes, it was Gold's hypothesis, not Dyson's. Also, are you forgetting that atmospheric carbon dioxide can dissolve in seawater and precipitate as calcium carbonate, i.e., limestone? No need for organic matter. If you recall the Miller-Urey experiment, life emerged due to the presence of natural gas, which emphasizes that not all natural gas is biogenic. $\endgroup$– Rodrigo de AzevedoCommented Oct 19, 2022 at 8:00
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$\begingroup$ Abiogenic petroleum origin. Ihttps://en.m.wikipedia.org/wiki/Abiogenic_petroleum_origin $\endgroup$– WouterCommented Oct 19, 2022 at 23:24
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2 Answers
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From your question you are obviously aware that gas deposit arise from life forms sinking to the bottom of shallow seas when they die, they accumulate over time and are subsequently covered by marine geological sediments.
Over time the thickness of the sediments increases. As the sediment thickness increases,
The weight of accumulating sediment very slowly pushes the source rock further under the Earth's crust, by a few meters to a few hundred meters every million years or so. This gradual sinking is called subsidence and leads to the formation of sedimentary basins.
I would qualify the above quotation in the source rock is pushed further into the Earth's crust, not under the Earth's crust, as pushing under the Earth's crust can suggest it gets pushed in the the Mantle or the contact region between the Mantle and the Crust.
The surface of the Earth is not static, it constantly moves, via a process called plate tectonics.
Additionally, different types of rock have differing degrees of flexibility and rigidity. Under various ground stresses rocks will fracture and faults and other discontinuities arise. Under certain situations the alignment of such faults can produce graben and horst structures. Horst structures rise while graben structures sink, mainly due to gravity.
Over time, sediments can fill graben structure and over the course of millions of years the original deposit of life forms ends up being buried deeply. At depth, the remains of the life forms are "pressure cooked" - subject to high temperatures and pressures - producing natural gas.
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$\begingroup$ Thx, especially the link to planete-energies.com/en/medias/close/…. But still if you think of it a few hundred meters every million years. This material should have come from somewhere. (Like mountains or vulcano's?) But at scales of millions of years... I guess it's possible. $\endgroup$– WouterCommented Oct 18, 2022 at 23:29
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A practical limit to commercial gas/oil drilling is 30,000 ft and generally not much deeper than 20,000 ft. The high temperatures and pressures are difficult to control. There are several mechanical limits like draw works power and casing strength ( commonly 125,000 psi yield steel is used and it is not strong enough for these wells.). It would be much easier to reach methane hydrate deposits on the sea floor if you can figure out how to produce it.
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$\begingroup$ Unfortunately, this doesn't answer the edited version of the question. $\endgroup$ Commented Oct 4, 2022 at 6:14
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$\begingroup$ I wasn’t asking how deep we can drill. Just how it’s even possible that it is stored so deep. As it is created by plankton. In seas. $\endgroup$– WouterCommented Oct 8, 2022 at 18:23
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$\begingroup$ Over geological time the rock moves. Also the is source rock nd reservoir rock; they may not be close. $\endgroup$ Commented Oct 10, 2022 at 0:23