A continuing slump in Soviet oil production, now in its 18th month, is putting a squeeze on Soviet leader Mikhail Gorbachev's plans for economic revitalization.

The problems in the oil industry -- a recurring theme in the Soviet press -- already have diverted badly needed resources from other areas of the economy.

The 1986 Soviet budget, adopted last November, called for a 31 percent increase in capital investments in oil. This was a significant jump that contradicted warnings from Gorbachev earlier this year that the energy sector -- already consuming one-fifth of the nation's capital investment -- would have to do without new infusions of capital.

Western analysts here interpreted the investment increase as a sign that Soviet economic planners have decided that the economy cannot afford to let the decline in oil output continue unchecked.

"It shows they are seriously concerned, and this is the minimum they have to do to hold the line," said one western diplomat.

Western estimates of 1985 Soviet oil production now hover at 597 million tons -- a drop of almost 3 percent from the 1984 level, which was already down 0.5 percent from the 1983 level of 616 million tons.

Because oil exports constitute 63 percent of Soviet hard-currency earnings, the decline has ramifications for other sectors of the Soviet economy.

The response to the troubles of the oil industry began developing before Gorbachev came to power last March. Earlier in the year, the oil minister was fired and replaced by Vasili Dinkov, who as gas minister had overseen the star performer of the Soviet economy.

In May, the ruling Politburo went ahead with a program to increase drilling by 40 percent in the next five years -- a bid to find replacements for the dwindling output from the country's older oil fields in the Tyumen region in western Siberia, where 63 percent of the nation's oil is produced.

But judging from the steady stream of critical articles in the press, the main problems in the oil industry continue. "Dinkov has been in long enough that some of these things should have been solved," said one analyst. "It looks like his honeymoon is over."

The attacks on the oil industry -- and particularly on the managers in Tyumen -- start with a litany of mistakes. According to the articles, in an effort to boost production to meet plan targets, oil was literally "gushed" out of wells using techniques that have made extraction at lower levels more difficult.

These problems have been compounded by failures in equipment, in local power systems, in transportation, in the siting of oil-dependent industries, in living conditions provided to the local work force.

The papers tell of cracked and rusting pipes, of one out of five wells standing idle, of wells that pump more water than oil, of continuing equipment breakdowns.

In trying to shore up the troubled industry, Tyumen managers have been relying on the Soviet system of shock brigades -- temporary workers flown in for special jobs. The cost is high, and the efficiency is low: One newspaper reported that the "nomad" workers are 30 to 50 percent less effective than local personnel.

Gorbachev got a firsthand look at the problems in western Sibera when he made a trip to Tyumen last September. His talk to workers there was one of his sternest lectures on the need to straighten out the Soviet Union's ragged economic performance.

The failure of the Tyumen oil fields to meet targets for three years in a row "creates difficulties for the national economy," he said.

The problems of attracting and keeping a reliable work force in the region was brought home to the Soviet leader by a worker in one Siberian oil town. Asked what Moscow could do to help him work better, the worker asked the Soviet leader to provide the town with a movie theater.

Despite the high-level personnel shake-ups and stern warnings, the trend in the oil fields has not abated. December figures, just released this week, show production slipping still further away from the 1985 plan target.

December also marked the 18th consecutive month that monthly production figures fell below the figures of a year before.

In recent months, the Soviet leadership has put together a major program of conservation and management aimed at preserving its oil reserves.

The 12th five-year plan, to be adopted at the February party congress, calls for 75 to 80 percent of increased domestic fuel requirements to be made up through savings.

The program also envisages continued conversion of oil-powered generating stations to nuclear energy and gas. The output from nuclear power stations is supposed to go up between 400 and 600 percent while gas output is expected to rise between 60 and 80 percent.

According to western diplomats, the goal of these efforts is to preserve oil supplies for foreign markets. At a time when oil prices are falling, costing Moscow $500 million in hard-currency earning every time it drops $1 a barrel, the Kremlin apparently had decided that it can ill afford any further losses.