Our good Mr Birkeland will probably be along soo to give some real documentation and knowledge, but I'll throw in a little I know from working around the "awl bidniss" for a while now.
The deep methane ideas are those of Thomas Gold, a polymath, maverick sort of guy who died just a month ago at 84. He worked with Hoyle, Bondi, and other big-name physicists and astronomers at various times. His ideas may have some merit - the deep gas in western Oklahoma was found by people who listened to him. But so very much petroleum has "biomarker" molecules in it that can be directly related to living things, even specific kinds of algae, or the cuticle on a kind of leaf, that I'm pretty well convinced that most oil is biogenic. A lot of natural gas may well not be, but that's not to say it's "primordial." There might be oxidation/reduction reactions in hot rock that could produce methane.
The "leaky caprock" bit turns up pretty often on creato sites, but I've never seen references or even numbers for the supposed "too-high" permeability of caprock. I strongly suspect that the permeabilities this claim is based on could be from cores from wells that were treated the standard way reservoir cores are: cleaned of oil, dried thoroughly, and perm measured with dry nitrogen at near-atmospheric pressure. That actually gives a pretty decent number for a highly permeable, clean sandstone, but may not in other cases. I remember a case of a tight gas sand in the Rockies that measured, say, one millidarcy under those conditions, but 0.001 millidarcy when confined at the pressure that the reservoir was actually at. (The wells didn't produce up to expectations at first.....) It may be that similar measurments on capping shales misled someone - a dried-out shale that's been depressurized from 10,000 psi to atmospheric is not in it's native state any longer, and those very low permeabilities aren't anything simple to measure accurately anyway. One invisibly small crack could easily let more nitrogen through that the matrix of the whole core surrounding it.
Reservoir rock having been hot (100 or 150 degrees C, for example) is not just a guess, either. For just one indicator,there's a substance called vitrinite that changes color depending on it's heating history - geologists use it to see if source rocks have been hot enough (or too hot) for optimal oil generation.
The article said that this phenomenon has been observed in many wells world-wide.
Hmmm. Where? I might want to invest.....
That happens a lot when humans intervene, like when waterflooding old reservoirs, but I've never heard of it just happening.
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