Conoco sees ease-off in US petroleum demand

-- Over the next several years oil prices will rise no faster than the rate of inflation.

-- US oil demand will continue to drop through 1990 and then start rising again. At the same time, gasoline demand will fall 2 percent per year and by the year 2000 will represent only 60 percent of the 1978 level.

-- Oil as a percentage of total US energy consumption will decline from 45 percent in 1980 to 34 percent by the year 2000.

--US dependence on imported oil will drop slightly by the year 2000.

These are a few of the conclusions reached by Conoco Inc. in a new study of the world energy outlook through the year 2000.

The big energy company, now a subsidiary of Du Pont, has each year analyzed the world supply and demand picture for oil. This is only the second year, however, that the company has released its findings to the public. In the past, its reports have been circulated internally, used by Conoco excecutives in their planning. According to Neil B. Bunis, director of industry studies at Conoco, the studies have nearly always identified the trends in the industry correctly even if they were off on their numbers.

In its latest study, Conoco is estimating that US oil demand will drop from 16.1 million barrels per day (b.p.d.) in 1981 to 15.5 million b.p.d. in 1990, before rising to 16.3 b.p.d. in the year 2000.

The key factors behind this forecast, in Conoco's view, are a trend toward more efficient use of energy, a slowdown in energy demand growth, and a shift to coal and other nonpetroleum sources. ''Oil demand has responded much more rapidly to prices than most people expected,'' Mr. Bunis says.

Also, the company is assuming that the economies in the United States and noncommunist world will show only moderate growth. ''The economic growth over the next 20 years,'' Bunis says, ''will be slightly better than the past seven years, but more modest than the early 1960s and 1970s.''

Bunis says this forecast also assumes that there might be some politically caused disruptions of oil supply. ''There are still some politically unstable areas producing oil. However, the US is less vulnerable than it was two years ago.'' Still, Conoco warns that ''the energy crisis is not over'' and the noncommunist world will remain susceptible to major oil supply disruptions through the rest of the century.

Even so, Conoco is estimating that oil imports will continue to decline, from 5.2 million b.p.d. in 1981 to 4.9 million b.p.d. in 1990 before rising again to 5.8 million b.p.d. in 2000.

US dependence on foreign supplies of oil, however, will rise to 36 percent of the nation's total petroleum requirements, from a current 32 percent. Because of major shifts in energy supplies, Conoco is estimating that imported oil will represent only 12 percent of total US energy demand by the year 2000, compared with 17 percent in 1980.

Coal will continue to make important inroads in energy use, Conoco, a major coal producer, maintains. Demand for coal, including exports, will increase 4 percent annually, from 800 million tons in 1980 to 1.2 billion in 1990 and 1.7 billion tons in the year 2000. Exports will more than double and coal as a percentage of total domestic energy consumption will increase from 20 percent in 1980 to 32 percent by the year 2000.

At the same time, natural gas consumption will drop from 20 trillion cubic feet of gas in 1980 to 19 t.c.f. in 1990 and 17.5 t.c.f. by 2000.

Nuclear power is expected to grow annually by 10 1/2 percent this decade and 3 1/2 percent in the 1990s as projects already under construction are completed.

Many of these trends will be in operation in 1982, industry analysts say. For example, the Department of Energy in its latest ''Short-Term Energy Outlook'' is estimating that total petroleum use will drop 0.7 percent this year, although imports will rise by 1.8 percent. US imports will rise, the DOE predicts, because of reduced inventories and the need to refill them. Domestic consumption , however, will fall for the fourth straight year. Gasoline usage will drop 1.2 percent and residual demand will fall by 6.2 percent as more utilities shift from oil to coal.

The department says stocks of home heating oil should be adequate for the winter season even though stocks are 11 percent lower than during last year's heating season. Oil companies maintain there is no problem getting supplies, so inventories can remain lower.