Crude prices above the magic century mark, with some knowledgeable observers predicting that they could double again within the next couple of years, have unleashed a flow of informative correspondence from the Foolish world. Indeed, many of the writers are energy professionals and therefore think about the subject daily. Let's look at some of the most recent comments we've received from oil and gas folks and energy investors alike.

Carbonates' thoughts
One Fool, a petroleum geologist who prefers that we call him "Carbonates," wrote following my recent article on Houston's Matthew Simmons, whom I called the "pied piper of peak oil" for his regular warnings that the global crude supply is about to fall short of demand. "Carbonates" clearly is a man after my own heart, given his positive feelings about Chesapeake Energy (NYSE: CHK) and its Barnett Shale successes:

The Barnett Shale opened a whole new paradigm in the industry's concept of what and how a gas reservoir works, and new gas shale plays (also called resource plays) are abundant and becoming less and less speculative every day. Chesapeake and Devon (NYSE: DVN) have been two of the biggest players in gas shales, and Chesapeake only recently announced entry into oil resource plays, so we are all waiting with baited breath to find our where they are at. Gas shales (and oil shales) are the new frontier in the oil and gas business and will soon spread from the U.S. to all international markets.

"Carbonates" also finds Simmons' contention that $200 oil could be in the offing -- a notion that I somewhat downplayed in my article -- to be plausible:

...for what it's worth, I don't think $200 oil by 2010 is unrealistic at all, especially with the current proposals that are coming from politicians running for office, but that's another subject entirely.

And to my observation that most of the major companies had suffered liquids production declines in the past quarter, he said:

The majors have a lot more problems with declining production than just the last quarter. Most of them have failed to replace annual production with new discoveries for about five years now, and Royal Dutch Shell just suffered a major reserve write-down. That does mean that they are liquidating their assets; however most have been buying back stock. The other offset is that the oil in the ground is becoming more valuable...Likewise, most of the majors are also in alternative energy -- BP (NYSE: BP), Chevron (NYSE: CVX) and Shell in solar, Shell and Chevron in biofuels, Shell in wind, Chevron in geothermal.

The role of alternative energy
Will, who also works in oil and gas, also paints an interesting picture for energy prices as they relate to the further development of alternative energy sources:

As the consumer price for gasoline increases, alternative energy sources will become more viable -- e.g. gas/electric hybrids, plug-in electric cars, hydrogen, natural gas, etc. I'm thinking that slowly more and more people that are not engineering nerds will buy into hybrid and alternative energy. Alternative energy demand and efficiency will slowly increase, the necessary infrastructure will slowly build up, and prices will go down. Alternative energy and oil prices will move in opposite directions, alternative decreasing and oil increasing...

...countries becoming 'industrialized' (like Vietnam and other third world countries who will begin to gain some share of the cheap labor market from China) will continue to increase demand on oil and easily accessible energy, just like the U.S. did. They'll do this until the oil runs dry.

Go, Hugo, go!
Finally, Fred took issue with my -- I hope only implicit -- backing of ExxonMobil (NYSE: XOM) in its standoff with Venezuela's Hugo Chavez:

Writing for a news outlet that gives investors advice puts you in the unfortunate position of seeing the world from a Big Oil perspective, a world where the market rules...Friedman economic perspectives. Seeing the world from the lens of Wall Street prevents one from really seeing how the story of individual lives are improved by keeping the money home and not going to some megarich corporation and group of investors on Wall Street. I say good for Chavez and I hope it happens again and again in other countries.

There you have it, a variety of thoughts on a subject that, if Simmons and "Carbonates" are even close to correct, will require our considerable attention (and resources) in the months and years ahead. I therefore urge you to share your comments or questions about oil and gas or other energy sources in our next Foolish Energy Mailbag.

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Fool contributor David Lee Smith doesn't have a financial interest in any of the companies mentioned. He does beseech you to send your comments, questions, or criticisms. The Fool has a disclosure policy.