That’s the correct Jeopardy question to the answer: “The lifetime during which the United States will run out of natural gas.”

In other words, we’ve got a lot of it. We may very well have more than a lot of it.

At least, we think we do. Until we develop the ability to see through solid rock, we can only estimate how much natural gas lies underground within the United States. This is why figures that you will see published are complex and often contradictory, because most people have a strong vested interest in presenting the figure as being either high or low, and there are many different sets of figures to choose from. We have discussed the complexities of this issue in a previous post, which you can read here.

Basically, the question of how much domestic natural gas we have comes down to a combination of three sub-questions: do we have geologic proof that it’s there, or are we just guessing; if we have proof, do we have the technology right now to get it out; and if we have the technology, does the current market allow us to actually put up wells and started producing profitably? Depending on how many “yes” answers you expect, the figure you end up with is very different. This is why you will hear people categorizing their totals using terms like “undiscovered recoverable resources.”

Here, in a nutshell, are the current best estimates.

If you’re going to hold your total to the highest possible standard, the United States has enough proven, recoverable reserves for the next ten years, assuming current usage.

If you’re willing to stretch your standard to include all the gas we know we can get at, that figure stretches to between eighty and one hundred and twenty years.

If you’re willing to stretch a bit farther, and assume that we will continue to improve our technology, the figure stretches into thousands, and perhaps even tens of thousands, of years.

Why are these figures so different? Because our whole conception of how we mine for natural gas has changed radically in the past decade. New drilling technologies now allow us to remove natural gas from geological formations that were previously thought impossible to tap.

The most important are shale deposits and coal gas deposits, particularly shale. We have only scratched the surface of what these new resources can produce. And it’s notable that most of these new resources are located throughout the lower 48 states, in fairly close proximity to existing pipelines.

The wild card, which might extend natural gas reserves beyond the foreseeable future, is a source we don’t yet know how to tap: huge deposits of frozen methane trapped under the ocean and the ice of Alaska. The potential here dwarfs all previous natural gas sources…indeed, all previous sources of all the fossil fuels.

This is bad news to a lot of people. For natural gas producers, it speaks of continued ample supply and, as a result, continued low prices. For green energy supporters, it takes some of the shine off the argument that fossil fuels are running out. And for investors, it raises doubts that they will see a repeat of the profits they took in the first half of 2008.

But let’s not forget: supply is only half of the equation when it comes to price. And future demand for natural gas, both domestically and internationally, is another question with many possible answers. It remains to be seen how the emerging economies of Asia and South America will rebound from the current economic downturn, and which energy source will fuel this rebound.

There are also many questions about the role natural gas will play, above and beyond it’s current usage, in America’s energy future. Will it power our cars? Will it replace coal as a way to reduce emissions for generating electricity?

We’ll keep you posted.