a reply to: Chrisfishenstein
By what we currently understand based on all the available field data involving igneous, sedimentary, and metamorphic rocks as well as experimental
data as collected in laboratories, yes. Unless you want to argue that the laws of physics are not as (relatively) constant on this macroscopic scale,
well, yes, millions of years for certain processes. Although, you might be interested to know that not all processes take millions of years.
Isostatic readjustment of crust has been happening in some areas over the last few tens of thousands of years (since the major glaciers melted).
As for actually viewing "replenishment" (not reproducing, they are finite in the system) from the "molten center" (sidenote: the center of the Earth
is solid and quite dense as demonstrable via seismic wave data... In fact, there are very few "truly" molten horizons in the center of the Earth.
Interesting subject, though.), well that's what the studies of volcanology and igneous petrology are for. You can see clear isotopic enrichment (most
prominently in some rare earth elements) in deep mantle-derived sources when compared to even shallow mantle sources. So yes, we have evidence of
crustal enrichment of certain things in the form of igneous bodies.
But igneous bodies are really more concerned with the heavier elements, not hydrocarbons. Hydrocarbons need to literally be cooked under the right
temperature and pressure conditions in order to be useable by humans. To argue against the slow formation of gas is rather strange... Based on
isotopic fractionation data, hydrocarbons in most oil and gas are from organic sources. The gradual build up of organic matter in deep ocean shales
(or trapped in coral reefs, or whatever else you have for a host rock) are first necessary. These organic remains then need to be buried by
successive layers of sediment. Eventually, the lithospheric block will begin to sink into the asthenosphere. With the successive layers building up,
pressure builds and the block lowers into hotter depths. To find the gas or oil, we must have access to it, so exhumation must occur after the basin
is filled with sediment or the sea must become shallower due to some other means (like being locked in ice). Notice the depth of sediment necessary
to create the pressure and heat...
The peak is about 3 km of depth. If you know of any quick processes that add 3km of sediment to ocean bottoms, I am legitimately interested in
knowing about them.
As for the wells "filling back up," that's again down to physical constraints. Remember that hydrocarbons are less dense than rock, so they tend to
rise (if they have sufficient ability to do so through joints and interconnected pores). Some hydrocarbons tend to "stick" to the grains of certain
host rocks (for a host of physical property reasons...), but the simple truth of the matter is that we cannot get every last drop of oil out of any
reservoir. If we take it slow enough, it replenishes from neighboring pores in the host rock. If we take it too fast, we lose lifespan for the rig,
but we could produce more (and leave more oil behind, if we speak about total sums). It isn't being made in the rock, though, it was always there.
I don't pretend to be smart about the Earth; it's too complicated a system. I do, however, think the models we create are more accurate then you
might be giving them credit.
As for the casings, yes, I have heard a properly installed casing these days is quite safe, in the sense that nothing is lost from the casing itself.
I was more worried about naturally existing joints in the rocks, or even porous interconnected spaces. I hear the problem is especially bad in
limestones. As for the propaganda, I tend to take a middle approach. I know fracking isn't perfectly safe, nor is it inherently harmful. It's hard
to tell where the methane in those "water on fire" videos comes from, considering the water likely travels through the same hostrock which contains
the hydrocarbons being targeted for fracking. In any case, I would agree that the hydrocarbons are not being "added" by fracking. I still support
fracking, and I agree that if done properly the risks are mitigated more than sufficiently. But as you say, we don't know everything about the
subsurface, and unexpected joints in limestones make for excellent conduits.
Again, I must say I enjoyed the discussion. Sorry for the rambling and long-winded responses.
edit on 13-8-2015 by hydeman11 because: Broken link to p/t chart
edit on 13-8-2015 by hydeman11 because: still