<p><a href="http://www.searchanddiscovery.com/pdfz/documents/2014/41427ishutov/ndx_ishutov.pdf.html" rel="nofollow">According to 3-D Printing Artificial Reservoir Rocks to Test Their Petrophysical Properties</a></p>

<blockquote>
  <p>Pore sizes of typical reservoir sandstone range from 0.1 to 100s of microns.</p>
</blockquote>

CC BY-SA 3.0
2015-05-18T03:17:32.493Z
That is indeed a cavern, if you are a bacteria!
Gimelist
CC BY-SA 3.0
2015-05-18T00:08:30.057Z
2015-05-18T00:08:30.057Z
DavePhD
<p><strong>A cavern filled with natural gas would look like an ordinary cavern. However, natural gas is rarely abundant in caverns.</strong></p>

<p>Most natural gas reservoirs occur in the pore spaces of sandstones. These pore spaces are generally up to about 1 mm in diameter. Here's a photomicrograph of a sandstone — the green-blue colour is the pore space; Q, F, L, and M are quartz, feldspar, lithic fragments and mica respectively:</p>

<p><img src="https://i.sstatic.net/badnU.jpg" alt="Helsby sandstone"></p>

<p>The pores of reservoir rocks also contain 'formation' water in various proportions. The relationship between the water and the hydrocarbons can be quite complex, depending on the fluid composition, the reservoir temperature and pressure, and the mineralogy of the rock.</p>

<p>So what about caverns? Trace amounts of methane probably occur in many, if not most, caverns — we're talking here about abundant methane. This is much less common, but it happens. In certain limestones pore spaces can be quite large — up to several metres in diameter. This is called <a href="http://en.wikipedia.org/wiki/Porosity#Types_of_geologic_porosities" rel="noreferrer">vuggy porosity</a>. If the limestone is charged with natural gas, the vugs will fill with gas, just like the other pores. The space would look like any other limestone cavity. Very large ones are rare, based on a typical <a href="http://en.wikipedia.org/wiki/Power_law" rel="noreferrer">power law</a> size distribution. There are (copyright and unlicensed) images of such super-pores <a href="http://www.geoexpro.com/articles/2013/06/heavy-oil-from-an-ancient-reef" rel="noreferrer">here</a> and <a href="https://www.spec2000.net/17-speccarb.htm" rel="noreferrer">here</a>. Recently <a href="http://www.sciencedirect.com/science/article/pii/S0012821X13002495" rel="noreferrer">Mattey et al. (2013; EPSL 374)</a> wrote about methane in a karst in Gibraltar. I'd estimate that less than 1% of the world's gas is held in vuggy reservoirs. </p>

<p>There's another kind of cavern in which you can find natural gas: man-made ones. Natural gas <a href="http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/storagebasics/storagebasics.html" rel="noreferrer">is often stored underground</a>, usually in porous rocks, but sometimes in caverns dissolved out of salt. <a href="http://www.eia.gov/todayinenergy/detail.cfm?id=3190" rel="noreferrer">Around a quarter</a> of natural gas stock is stored this way in the US. <a href="https://www.youtube.com/watch?v=ThbkFfXjhxk" rel="noreferrer">Here's a video</a> from such a salt cavern.</p>

<p>Last thing: methane seas can only occur at low temperature. As far as I know, <a href="http://en.wikipedia.org/wiki/Liquefied_natural_gas" rel="noreferrer">liquefied natural gas or LNG</a> is only stored above ground or on ships in tanks. Lots of natural gas reservoirs have <a href="http://en.wikipedia.org/wiki/Natural-gas_condensate" rel="noreferrer">very light hydrocarbon liquids</a> in them — but again the liquid would be in tiny pore spaces, not caverns.</p>

CC BY-SA 3.0
2015-05-20T11:41:13.333Z
Someone at BGS [just tweeted](https://twitter.com/CliveBGS/status/600986837663010816) about salt caverns for gas storage.
Matt Hall
CC BY-SA 3.0
2015-05-18T12:03:45.190Z
2015-05-18T12:03:45.190Z
Matt Hall
<p>I suppose natural gas underground caverns on Earth have substantial volume and gas is in gaseous form there.</p>

<p>As such I wonder how it would look like inside such cavern (with artificial light of course). Will one see a rocky sky at big distance?</p>

<p>What is the actual volume of such caverns? It is correct to talk about methane oceans or seas?</p>

<p>Are they empty or the gas is mixed up with solid substance?</p>

CC BY-SA 3.0
2015-05-17T20:03:31.927Z
[Cross-posted on Worldbuilding.](http://worldbuilding.stackexchange.com/questions/17402/what-does-it-look-like-inside-a-natural-gas-caverns-on-earth) Please don't do this.
HDE 226868
<geology><gas><cavern>
What's it like inside a natural gas cavern on Earth?
Anixx
# What's it like inside a natural gas cavern on Earth?

(Asked by: username_0 on 2015-05-17)

I suppose natural gas underground caverns on Earth have substantial volume and gas is in gaseous form there.

As such I wonder how it would look like inside such cavern (with artificial light of course). Will one see a rocky sky at big distance?

What is the actual volume of such caverns? It is correct to talk about methane oceans or seas?

Are they empty or the gas is mixed up with solid substance?

**Tags:** geology, gas, cavern

> **Comments:**
> **username_1**: [Cross-posted on Worldbuilding.](http://worldbuilding.stackexchange.com/questions/17402/what-does-it-look-like-inside-a-natural-gas-caverns-on-earth) Please don't do this.  

---

## 2 answers

### Answer by username_4 on 2015-05-18. Score: 14 | Accepted answer

**A cavern filled with natural gas would look like an ordinary cavern. However, natural gas is rarely abundant in caverns.**

Most natural gas reservoirs occur in the pore spaces of sandstones. These pore spaces are generally up to about 1 mm in diameter. Here's a photomicrograph of a sandstone — the green-blue colour is the pore space; Q, F, L, and M are quartz, feldspar, lithic fragments and mica respectively:

![Helsby sandstone](https://i.sstatic.net/badnU.jpg)

The pores of reservoir rocks also contain 'formation' water in various proportions. The relationship between the water and the hydrocarbons can be quite complex, depending on the fluid composition, the reservoir temperature and pressure, and the mineralogy of the rock.

So what about caverns? Trace amounts of methane probably occur in many, if not most, caverns — we're talking here about abundant methane. This is much less common, but it happens. In certain limestones pore spaces can be quite large — up to several metres in diameter. This is called [vuggy porosity](http://en.wikipedia.org/wiki/Porosity#Types_of_geologic_porosities). If the limestone is charged with natural gas, the vugs will fill with gas, just like the other pores. The space would look like any other limestone cavity. Very large ones are rare, based on a typical [power law](http://en.wikipedia.org/wiki/Power_law) size distribution. There are (copyright and unlicensed) images of such super-pores [here](http://www.geoexpro.com/articles/2013/06/heavy-oil-from-an-ancient-reef) and [here](https://www.spec2000.net/17-speccarb.htm). Recently [Mattey et al. (2013; EPSL 374)](http://www.sciencedirect.com/science/article/pii/S0012821X13002495) wrote about methane in a karst in Gibraltar. I'd estimate that less than 1% of the world's gas is held in vuggy reservoirs.

There's another kind of cavern in which you can find natural gas: man-made ones. Natural gas [is often stored underground](http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/storagebasics/storagebasics.html), usually in porous rocks, but sometimes in caverns dissolved out of salt. [Around a quarter](http://www.eia.gov/todayinenergy/detail.cfm?id=3190) of natural gas stock is stored this way in the US. [Here's a video](https://www.youtube.com/watch?v=ThbkFfXjhxk) from such a salt cavern.

Last thing: methane seas can only occur at low temperature. As far as I know, [liquefied natural gas or LNG](http://en.wikipedia.org/wiki/Liquefied_natural_gas) is only stored above ground or on ships in tanks. Lots of natural gas reservoirs have [very light hydrocarbon liquids](http://en.wikipedia.org/wiki/Natural-gas_condensate) in them — but again the liquid would be in tiny pore spaces, not caverns.

> **Comments:**
> **username_4**: Someone at BGS [just tweeted](https://twitter.com/CliveBGS/status/600986837663010816) about salt caverns for gas storage.  

---

### Answer by username_2 on 2015-05-18. Score: 4

[According to 3-D Printing Artificial Reservoir Rocks to Test Their Petrophysical Properties](http://www.searchanddiscovery.com/pdfz/documents/2014/41427ishutov/ndx_ishutov.pdf.html)

> Pore sizes of typical reservoir sandstone range from 0.1 to 100s of microns.

> **Comments:**
> **username_3**: That is indeed a cavern, if you are a bacteria!  

---

