FOR THE past seven years, forecasts of future oil availability -- especially those based on price -- have regularly been out of date by publication day. In general, the estimates of how much oil can be produced have tended to be overstated, while the potential of conservation programs has been underestimated. Despite the record of error, and the large uncertainties, forecasts of future oil supply are important nonetheless: without them, prudent policy-making is impossible.

The Iranian revolution of last January not only removed most Iranian oil production from the world balance sheet.It also demonstrated to other major producers the disruptive social effects of too rapid oil development. For both reasons, forecasts made before that upheaval are pretty much obsolete. Of the few that have been attempted since, one of the most sobering was released this week by the congressional Office of Technology Assessment.

The report emphasizes the great uncertainties involved in predicting world supply for even as short a term as the remainder of this decade. But it describes as "highly likely" the prospect there will be little or no increase in total world oil production by the end of the century. On the other hand, there will certainly be substantial growth in energy demand, at least in the developing world. Assuming -- and it is a big assumption -- "political stability in the major exporters," OTA predicts a non-communist world oil supply of 40 to 60 million barrels per day in 2000, as compared with 52 million barrels per day last year.

The sharp decline in predicted U.S. production is one of the major factors in this rather grim picture. OTA's estimate of U.S. production ranges from less than half of today's level to a high of about one-third less. And the high estimate depends on both the annual addition of one billion barrels to domestic proven reserves and vigorous use of expensive new recovery techniques that can extract more oil from wells that have already been conventionally exploited.

On the positive side, OPEC oil production is expected to remain about constant, limited by political-economic decisions to restrict production rather than by geological constraints. Increases in production in other developing nations, including Mexico, are likely to be offset by growth in demand in these countries. Nor does the study hold out much possibility for production from major new oil finds outside the Middle East.

The OTA report's final estimate covers a fairly broad range of possibilities -- from 20 percent less than today's oil supply to 15 percent more. But even the high end of the estimate -- which depends on some very optimistic assumptions -- allows hardly any room for economic growth unless ways are found to reduce wasteful energy uses in the meantime. Considering the likelihood that supply may actually turn out to be closer to the low end of the estimate, the report's message can be taken as a strong warning against any sense of complacency that this country's energy problems are yet under control.