Three years after a Goldman Sachs analyst made what seemed at the time a bold forecast of $105-a-barrel oil, he has a new target: prices as high as $150 to $200 a barrel in the next six to 24 months.

"We believe the current energy crisis may be coming to a head, as a lack of adequate supply growth is becoming apparent," the Goldman Sachs analyst, Arjun Murti, wrote in a note to clients.

The recent note is an apparent update of a report in March, when Goldman suggested that $200-a-barrel oil was a possibility in the face of a major disruption of supplies or a recovery in the U.S. economy.

Now it is one of two likely scenarios outlined by the analyst: either a gradual rise in prices to $120 a barrel or a "super spike" to $200.

The latest Goldman report points to supply constraints for both OPEC and non-OPEC producers. And the report pooh-poohs the idea that the rise in oil prices is driven by a speculative bubble.

"Unfortunately, we do not think the energy crisis will be solved by finding and punishing the big bad speculator," the report says. (Goldman Sachs is a major trader of oil and other commodities.)

The report cautions, however, that predicting a peak in oil prices "remains a major uncertainty."

In March 2005, Murti said that the oil market had entered the early stages of a multiyear super-spike period during which prices could climb as high $105 a barrel. Oil was trading in the $50-a-barrel range at the time. This March, oil traded above $105 for the first time ever.

In trading today, oil climbed above $121 a barrel. Prices rose after a weekend rebel attack in Nigeria disrupted supply.

Oil at this level is a bad sign for the U.S. economy. In January, Daniel Yergin of Cambridge Energy Research Associates estimated that oil prices would have to average $100 to $120 a barrel for six months to a year in order for higher prices to have the same kind of impact on the economy that the oil shocks of the 1970s did.