Nice post, I think you're spot on.

For overburden, in the coal business I think it's profitable to strip mine a seam if the ratio of coal bed thickness to overburden thickness is more than 1 to 20, i.e., if the coal seam is 20 feet down, it needs to be at least 1 foot thick. My guess is that most oil reservoirs are too deep, as I think they tend to be thousands to tens of thousands of feet deep, e.g., the "oil window" where P & T are high enough to created oil from kerogen is 7,500-15,000 ft burial depth. The exception of course is tar sands, which are oil reservoirs with no cap rock, so the oil "floated" (seeped) to the surface.



One other point, pump jacks will be able to pump oil from a depleted reservoir for a long time. The issue is not just if we can get the oil out, it's at what flow rate.

I would think that a lot of this depends on the physical structure of the porosity; so a lot would depend on the local geological structure.

Also, the viscosity as it relates to the Reynolds number and size of micro pathways in the rock would also affect how fast it would (re)collect in recoverable pools (after a rest period).

Re: Mining Oil

No worries. At the "oil window" (7,500-15,000 ft depth)* it's only hot enough to bake human skin within minutes... Not to mention the problems due to the high geological pressures there...

Depth of the Deepest Mine

...Many problems arise when digging so deep into the Earth. The most obvious is the heat. For example, at 5 km the temperature reaches 70 degrees Celsius and therefore massive cooling equipment is needed to allow workers to survive at such depths. Another problem is the weight of the rock. For example, at 3.5 km the pressure of rocks above you is 9,500 tones per meter squared, or about 920 times normal atmospheric pressure. When rock is removed through mining this pressure triples in the surrounding rock. This effect coupled with the cooling of the rock causes a phenomenon known as rock bursts, which accounts for many of the 250 deaths in South African mines every year.

...But, in the future human labor will be cheap and people expendible.

*borrowed from Gwydion

It would probably be much more economical to send gangs of laborers out on to the highways and parking lots with pick axes, shovels, and wheelbarrows to "mine" the asphalt. I can imagine this actually happening at some point in the future.

It takes giant earth moving machines to make the oil sands profitable. In a deep mine the oil soaked rock would have to be chipped out by miners and hauled out one tiny car load at a time. The energy expanded to extract would be far greater than the energy contained in the extracted material.

Ron,

IIRC, only about 18% of the oilsands can be mined from the surface. The remaining 82% is accessible by techniques such as SAGD (Steam Assisted Gravity Drainage).

Here is what the surface facilities of a SAGD operation look like:

link

And a photo gallery of the whole Long Lake site can be found here.

The Long Lake project converts part of the bitumen into a synthetic gas which is used in place of NG for heat.

We don't use miners with pickaxes in the oilsands at the current time :)

Hmmmm ... beware being quoted out of context ... actually, what I said was:

'Net Exports' Peak Oil is primarily an energy problem, specifically for transport in importing countries, there has to be more energy in the oil than is used to obtain it for transport uses but there is no need to worry about EROIE for chemicals and plastics.

There is enough known oil to last hundreds of years for chemicals/plastics - URR reserves of oil economical for energy uses are much smaller than total reserves.

When an oil well's production for energy is energetically uneconomic the rest of the oil (the majority?) left behind can still be extracted some other way if somebody is willing to pay the price - Canadian Tar Sand mining is an example where the deposit is close to the surface.

Darwinian says:

Oil wells are drilled because they are deep

I think this is incorrect, oil wells are drilled because they are currently the cheapest and most profitable way to get at the oil. It looks like in certain places it is even profitable to actually mine hydrocarbons for energy use - but this won't last!

There are many very useful non-energy uses for oil (and other fossil hydrocarbons) and this is the way most of the world's population gets to use oil currently.

When the world's oilfields have been depleted of 'net energy' what remains can be extracted in some way if, as I suspect, it will be profitable to do so - though not in a way that Darwinian can envisage it seems.

I have seen underground oil sand mined - using what is known as borehole mining - in Bakersfield back in the last energy crisis. I was on my way to JPL where we discussed an alternative version where long laterals were to be drilled and mining carried out from them, again using water jets as the mining tool.

The oil in Alberta is readily separated from the sand in the pumping operation that carries it from the floor of the pit up to the refinery. It is possible to do the same sort of thing with the underground mining operation, stripping the oil and then pumping the sand back underground. I have seen the same tool used in mining small uranium pods in Wyoming - mine the sand, remove the uranium, pump the sand back into the underground cavity - regrade the surface and move on. (In fact I taught this in class a couple of weeks ago).