There is a lot of worry in the public domain these days about whether we might be running out of oil. That shouldn’t surprise — every time the oil industry goes through a boom cycle (and there have been six such price booms since the creation of the industry in the late 19th century), industry analysts and resource prognosticators have warned that, this time, the lights are truly going out.

The worry, however, is overly broad. There is virtually no limit to the amount of hydrocarbons available to the economy. It has been estimated, for instance, that the amount of oil that we could theoretically extract from shale rock in the western United States is about three times as great as the proved reserves of oil in Saudi oil. Other unconventional sources of oil such as tar sands (now being exploited with gusto in Alberta) promise even more.

But unconventional oil is expensive. The reason it’s not exploited very aggressively at the moment is that conventional oil is still less expensive to deliver to market. If conventional oil continues to increase in price — or if the technology related to unconventional oil extraction improves — that might change.

Worries about the depletion of conventional oil — and light crude oil in particular — are better grounded. But how much better?

To worry about the future availability of light crude is to worry about the future availability of Persian Gulf crude oil in general and Saudi crude oil in particular. If Saudi fields are running dry, then worries about conventional crude are probably well placed. If not, then they probably aren’t.

The most credible analyst who’s made the argument that Saudi reserves are overstated and that Saudi Aramco is near a production plateau is Matthew Simmons, author of Twilight in the Desert. The most impressive criticism of Simmons’ arguments come from energy economist Michael Lynch, who maintains that Saudi production is not even close to reaching its peak.

Time will tell soon enough who’s right (I’d bet on Lynch), but in the meantime, a new report out today about Arab investments underway in the oil sector suggests that someone forgot to tell OPEC that the wells are running dry. Of course, one might argue that all that money is necessary just to maintain current production levels. Maybe — but the increasing production figures coming out of OPEC aren’t figments of the imagination.