Let's talk about the somewhat -- no, tremendously -- daunting phenomenon that we'll almost certainly be facing in the not-too-distant future: $100 per barrel of oil. We're already in the 90s and trending upward. I well recall that, as an operative of Pennzoil Company -- now part of Royal Dutch Shell (NYSE:RDS-A) (NYSE:RDS-B) -- earlier in my career, I knew $100 crude was on the horizon. The big surprise is that it didn't arrive far sooner.

Let's look for a minute at the reasons that crude has gone from around $60 per barrel to almost $100 per barrel just this year. Of course, there's supply and demand. Specifically on the demand side, we realized a few years ago that the nations of the developing world (read, China and India) were using far more petroleum products each year, with little likelihood that their new growth rates would subside.

There also are other factors, such as increased futures speculation in the oil markets, a relatively new phenomenon that's raised the crude price by goodness knows how much. Beyond that, many of the producing nations -- I'm thinking about such places as Venezuela, Nigeria, Iran, Iraq, and, yes, Russia -- are at least somewhat less than dependable politically. During this year, fear has increased that one or more of those garden spots could erupt, playing havoc with the fear premium in the oil price.

Last, but not least, are the sliding U.S. dollar and percolating concerns that, while global demand for oil continues to rise, the world is slowly losing its ability to increase production apace. It's my conviction that the latter consideration will only increase in importance in the years to come.

I'm also virtually certain that we haven't felt the full economic effects of higher oil prices and the resulting hikes at the gasoline pump. Obviously, lots of goods and services, from airline tickets to clothing, are destined to follow suit with higher levies of their own. And I fully expect the sizable paycheck-to-paycheck crowd to begin pulling back on all manner of expenditures as they begin to feel a more perceptible financial pinch.

As to the place to put your money amid expensive oil, I've seen all sorts of suggestions in the past several days, from defense contractor Lockheed Martin to biofuels facilitator (among other things) Monsanto (NYSE:MON). For my money, the best place for your investment pennies -- as we watch the world intensify its search for hydrocarbon reserves -- is still the oilfield services providers, such as Schlumberger (NYSE:SLB), Halliburton (NYSE:HAL), Transocean (NYSE:RIG), and Diamond Offshore (NYSE:DO).

So, Fools, it may not be over just yet. With the price of oil skyrocketing, industries beyond oil will feel the pinch, as will consumers. Keep an eye on the implications of $100 oil -- it's going to be a bumpy ride to the gas station.

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does pump gasoline more frequently than he'd like, though, and he also welcomes your questions or comments. The Fool has a disclosure policy