While that flame was hardly magical, the colorless fuel that powered it certainly ranks as one of the most important human discoveries of all time. That same mysterious gas is now one of the most valuable commodities on the planet and is quite literally powering growth all over the world.

The temple at Delphi was only the first of many structures and human endeavors fueled by natural gas. The magical flame was caused by gas seeping slowly from the Earth -- a common natural phenomenon in parts of Greece. That famed temple flame was, most likely, ignited by a simple lightning strike.

Gas has been put to practical use as a source of heat and light for well over 2,000 years. Five hundred years after the Oracle of Delphi was constructed, the Chinese built bamboo pipes to carry gas from similar seeps, using it to boil water and desalinate seawater. And starting in the summer of 1816, the streets of Baltimore, Maryland stopped going dark every evening after they installed streetlamps powered by natural gas.

Nowadays the world is more dependent on natural gas than ever. Because gas burns much cleaner than coal or oil, it has become the fuel of choice in modern-day power plants. Meanwhile, many consumers rely on natural gas to power their stoves, ovens and heaters. This is not only a U.S. phenomenon -- major gas-fired power plant construction projects are underway across Europe and in fast-growing markets like India and China.

Simply put: Natural gas is by far the world's fastest growing mainstream fossil fuel. And going forward, as you can see in my chart, this trend is likely to continue for some time to come.

Since 1965, global consumption of natural gas has nearly quadrupled to more than 260 billion cubic feet per year. Meanwhile, crude oil consumption is up roughly 2.5 times.

According to the U.S. Department of Energy (DOE), U.S. consumption of natural gas is projected to rise by nearly +40% between now and 2025. And electricity demand is growing even faster in developing markets like China and India; these countries are building gas-fired power plants to meet part of that demand. The DOE projects a more than doubling in gas demand across the emerging markets by 2025.

Looking at the longer-term picture, the tidal wave of global gas demand is an important consideration. As global demand rises and producers struggle to keep up, gas prices are likely to rise over the long haul.

How to Profit from Natural Gas
When many investors think of natural gas firms, they think first of their local distribution company, or "LDC." LDCs are normally utility companies that own the smaller pipes that carry gas around a particular city or county. If you use gas to heat your home or as a fuel for your stove, then the LDC is the company that sells you that gas.

But LDCs do not provide investors with a good way to profit from higher gas demand and pricing. In fact, contrary to popular belief, higher gas prices are normally a big negative for LDCs.

The reason for this is simple: LDCs charge regulated rates for gas -- rates that are set by state and local governments. Those rates are normally made up of three separate components: a base hook-up fee, a commodity fee, and a fee based on gas throughput.

The base hookup fee is relatively fixed. Meanwhile the commodity fee moves up and down based on natural gas prices. And finally, the throughput fee rises and falls based on how much gas is consumed.

Most LDCs do not explore for and produce their own natural gas. Instead, they buy gas from third-party producers. Thus, while your gas bill might rise due to an increase in the commodity component, most or all of that simply gets passed through to the gas producers who sell to the LDCs.

Meanwhile, when natural gas prices are high, the throughput fees that LDCs earn tend to decrease due to the impact of gas conservation. The reason is simple -- when gas prices rise, consumers usually turn the thermostat lower in the winter and/or take steps to conserve energy in other ways. That leads to less energy consumed, and therefore lower throughput charges for LDCs. This is bad news for your local gas utility firm.

In an effort to recoup this lost revenue, LDCs will usually apply for rate increases from their state and local governments. However, these types of requests are often denied. After all, politicians would find themselves in hot water if they voted for higher natural gas fees.

So, if LDCs don't benefit from rising natural gas prices, then who does? The firms that benefit are exploration & production (E&P) companies. These firms actually explore for natural gas reserves and sell that gas production. As such, E&P companies usually profit handsomely from natural gas prices increases.

Of course, there are literally hundreds of E&P companies available to investors, and not all are equally good plays on rising gas prices. A few of the key factors to consider when evaluating an E&P stock include:

• A focus on natural gas. Most E&Ps explore for some combination of oil and gas. If you feel that natural gas prices are likely to see the most upside, then you should focus your research efforts primarily on natural gas E&Ps.
• Political risks. Natural gas is found all over the world in developed, stable countries like the U.S. and UK, as well as in more volatile places like Nigeria, Russia, and the Middle East. Some countries demand higher taxes and tariffs from producers than others -- leading to lower profits.
• Size of reserves. Natural gas exploration can be a risky business, and even finds that look promising at first can come to naught. Some E&Ps have large proven reserves. Meanwhile, other riskier firms rely exclusively on new exploration to find reserves.
• Quality of Reserves/Cost. Some reservoirs, especially more mature, fully exploited reserves, are expensive to produce. Companies with lower production costs see the best margins and benefit most from rising pricing.

In the table below, we provide you with a long list of large E&P firms that operate all over the world. You may want to perform further research on these companies, since rising global demand bodes well for investments in natural gas related securities.