Yea, maybe it was a one room school house, it has been so long ago I hardly remember. But some things you just don't forget, like the dinosaur theory of oil.
I believe we really don't know and with that, anyone's theory could be equally viable. I'm don't pretend to know anything about how oil is formed, but rather just throw it out here for discussion and see what we bring in with responses. Your idea about pressure I think is part of the equation, and that would help explain why so many oil fields are located under the oceans and large bodies of water. Water weighs a little over 8 pounds per gallon, all that weight pressing on the bottom of the ocean floor could be a critical factor.
I have a handful of friends that work in the oil field, those wells I mentioned coming back on line weren't drilled any deeper, the slipped in new casings and pumps and are pumping from the original depths.
About a mile down the road from me a family friend has an old natural gas well that is capped off, and has been from 1970, back in 2005 the cap split from rusting and the well was spewing natural gas. The crazy bastard put on his scuba tank and grabbed a big pipe wrench after he had picked up a 4" gate valve from the plumbing supply store and when out and unscrewed the rusted cap, then threaded the gate valve on the exposed pipe threads, with the valve wide open. Once he had the valve tight on the pipe he started closing the valve, he said the only problem he encountered in his plan was when the valve was damn near closed all the way the whistling noise was so loud he thought it was going to bust his ear drums. He said next time he would use ear plugs too.
But that gas well had been abandoned just like the other oil wells because the production just wasn't there, no telling how much gas is in there now, and now there are subdivisions all around his 5 acre tract of land.
I still can't wrap my head around how nothing can explode into something so massive as our universe? Nothing from nothing is still nothing, and nothing times nothing is still nothing... so nothing can't end up being something no matter how you work it in my book. The big bang is a bust with me.