From this sturdy wellhead platform three miles by causeway from the western shore of the world's largest inland sea, Soviet oilmen are steadily pumping energy from one of their nation's most historic and reliable petroleum fields.

Along the shoreline of the Caspian Sea, north of the Azerbaijani capital of Baku, the land and sea are thick with derricks and hobbing donkey pumps providing oil for the industries and home of European Russia. The work began in the early part of the century and made Baku the traditional oil capital of the Soviet Union.

Its products powered the Red Army offensives that hurled back the Germans in World War II and, together with other major fields west of the Urals, helped fuel rapid postwar growth in the Soviet economy.

Workers here made up to 400 rubles ($520) a month, well over the Soviet industrial average of 175, according to Musaev Feredun, the site chief, and they compete hard for bonuses available to teams that drill faster and deeper.

The men and women of this station commute over the concrete one-lane causeway that connects 236 separate wellheads -- part of a vast shallow-water oil production complex built above the Caspian Sea's sandy bottom. The complex includes a unique oil community on stilts called Peschanoye More, where 1,500 technicians, roustabouts, repairmen, drillers and construction workers spend eight- or nine-day shifts at work.

This technical feat brings proud grins to the faces of Feredun and his colleagues. The causeway operations also serve as an ironic symbol of the shortcomings of the local oil industry, a small but important piece in the puzzle of the troubled Soviet petroleum economy.

What happens here and in other remote areas of the Soviet Union may affect Amreican oil prices in the next decade.

This is because the Soviet Union also is in the throes of an energy crisis. As in the United States, there is no easy solution. A danger, from the West's point of view, was predicted in a now famous CIA study in 1977. It said the Soviets will be net importers, not exporters, of oil in the mid-1980s. Should that happen, skyrocketing world oil prices could head for the next galaxy.

Although officials estimate they have many decades more before the easily accessible Baku reserves run dry, Caspian offshore production has fallen short of its targets in recent years, static at about 70 million barrels per year, or roughly two percent of the Soviet Union's 1979 record production of 4.1 billion barrels.

While officials predict they will make the overall five-year plan goals, the search for new areas is limited by the severe technical limitations of this oil center. According to the area's chief oil and gas geologist, Knochtbacht Usufzade, the Soviets do not have the know-how or hardware to explore in water deeper than about 300 feet. By his estimate, this means that about 40 percent of the offshore Caspian basin reserved for oil prospecting is beyond reach.

The same limitations apply to other Soviet offshore areas in the White Sea, Black Sea, Barents Sea and off Sakhaliin island in the Pacific. In U.S. and other offshore areas, exploration and production proceeds at twice that depth. Some wells have been drilled from 1,000 feet above the sea floor.

The Soviets' lag in offshore exploration coincides with a general drop in production in most of the relatively shallow an easily accessible oilfields in European Russia. Although the Soviet Union is by far the world's largest oil producer, half of its total comes from enormous Siberian fields in the basin of the north-flowing Ob River.

Western analysts say they have found increasing evidence that the remarkable production pace in the severe Siberian climate has been achieved at considerable cost to the older areas, which have sent technicians and equipment to the northeast.

Meanwhile, the massive Siberian effort also is encountering problems. Recent Soviet press accounts show that drilling in the key Tyumen Oblast is 200 wells behind schedule, amid complaints that efficiency has declined because new workers are not prepared for the rigorous climate.

The 1980 target for this vast oilfield is 2.1 billion barrels, an increase of 70 million from the 1979 output. Some Western analysts think the Soviets will be hard pressed to achieve the goal.

Like Soviet planners elsewhere who are looking for help, Baku officials say a long-awaited infusion of Western know-how will solve their immediate problems and lead to greater output. They are counting for great help from a $50 million semisubmersible oil prospecting rig bought from Armco Steel Corp. now being assembled up the seacoast in Astrakhan. This rig can operate far below the 300-foot limit to find new reservoirs and help the Soviets perfect the deep-water techniques they now lack. Geologist Usufzade said there are plans for building similar rigs, with Western help, to explore other offshore areas.

But the Soviets are notorious for slow results in applying new technology. The gap between target and real output may well widen in the coming years.

President Leonid Brezhnev, confronted by grim figures showing a slowdown in economic growth, has made clear that Societ economic well-being is tied directly to increased exploitation of petroleum reserves. Controversy surrounds both the amount of oil reserves and probable production rates.

The Soviet Union has the world's second largest known oil reserves, generally said in the West to be about 71 billion barrels. But a Swedish firm, Petrostudies, specialists in Soviet petroleum, in a recent report more than doubled that to 150 billion barrels. The Soviets themselves will not say; oil reserves are a state secret.

The 1977 CIA report, somewhat revised but still accepted by many as plausible worst-case projections, predicted production problems soon, caused chiefly by improper extraction methods. The Soviets angrily reject this and the Swedish analysts reached a far different conclusion: that the Soviets have effectively reorganized their oil, gas, and geology ministries with an eye to becoming a major seller of refined petroleum products in the world -- and soon.

In any case, while the Soviets extract far more than the next largest producer, Saudi Arabia, (with about 9.5 million barrels), they are lagging below their own goals.

For 1980, Soviet oil production is set at 4.2 billion barrels, 148 million more than in 1979, but 238 million below the original peak production targets set by the state in the five-year plan adopted in 1976. Western analysts doubt whether even the current goal can be met, despite Brezhnev's anger and criticism.

Soviet oil production is not only crucial in the national economy but also in earning hard currency abroad. The Soviet Union is the third largest oil exporter after Saudi Arabia and Iran: about 3 million barrels exported daily, with slightly less than half going to Western, hard-currency markets. Hard-currency earnings from oil total about $6 billion annually, about half of the Soviet overall total.

Most of this money is used to buy Western technology, such as the Armco offshore oil rig or the $150 million Dresser Iindustries oil drill plant, the sale of which was held up by President Carter in 1978 in retaliation for Soviet trials of dissidents.

Thus oil trade is crucial to modernizing Soviet industry, whose manufactured goods are not up to world standards.

Lower-than-expected oil output could affect this trade, since the Soviet economy is making larger demands for petroleum yearly and the Soviets have promised to increase by 20 percent their oil exports to the Eastern bloc, according to a Radio Moscow report last July.

If the Soviets cannot meet these promises, the East Europeans, with rising energy needs, will be forced to buy more in Western markets.

If Moscow cuts oil shipments to Western countries, such as Finland and West Germany, they likewise will be forced into greater reliance on Western markets -- adding pressure on prices.

Such considerations affected White House thinking when Carter reversed himself at the end of 1978 and cleared the sale of the Dresser drill bit plant. One of the grounds for that decision was that the West has a direct economic interest in aiding the Soviets to raise their oil production.