The Central Intelligence Agency has issued new estimates that sharply downgrade the oil-producing capabilities of Saudi Arabia, the world's largest oil exporter.

The Jan. 11 estimates by the CIA's Office of Economic Research have been eyed with skepticism by some oil analysts in the government as well as in the major oil companies.

In its new appraisal, the CIA pegged available Saudi productive capacity at 8.8 millions barrels cited last year.

Oil analysts questionins the CIA conclusions are also skeptical about the reduction in the agency's public estimates of the oil carter's underulilized or so-called "spare" production capacity. This calculation has been cut to 2.5 million barrels a day from 9.4 million.

The CIA's public estimates of Saudi productive capacity are supported by a separate, highly classified analysis of Saudi oil policy and the conditions of the Persian Gulf country's oil fields. That analysis, which has not been made public, says the new capacity estimates are justified for three primary reasons:

Political constraints in the staunchly conservative pro-American kingdom will increasingly move the Saudi regime toward reining in Production. The agency concludes that Saudi rulers will place more weight on arguments by some technocrats tht their oil is worth more in the ground for future production than it is produces for Western markets.

Financial outlays needed to increase production - set now at a up to $25 billion or more to increase capacity to 14 million barrels a day, and to complete a county-wide gas gathering project - considered by some Saudis as too high, and not worthy spending.

Finally, technical problems. though correctable, have resulted in loss of pressure and production in some wells. This is due, the analysis says in part, to failure to upgrade pumps, waterflooding equipment and other oil field equipment.

The new CIA estimates were made public following Energy Secretary James R. Schlesinger's return from a fact-finding visit to Saudi Arabia, where he met with Crown Prince Fahd, Oil Minister Zaki Yamani and officials of Arabian American OIl Co. (Aramco)

Assumptions about the Saudis' capacity to produce oil as well as the cartel's spare oil production capacity are critical to projections, such as President Carter's, that the United States faces a world oil squuze in the 1980s.

Moreover, with a fourth of the world's proven oil reserves, Saudi Arabia - the oil's cartel's leading producer - is acknowledged to be the greatest potential source of oil production over the next decade to meet the industrialized countries' mounting import needs.

Energy officials say the CIA analusis is based on new intelligence.

Of the Saudis' oil capacity, a CIA spokesman said, "The decline in those figures represents a shift, in part, of CIA estimatres of available productive capacity. That is our official explanation - we cannot go beyond that."

Schlesinger, who headed the CIA during the Nixon administration, ahs embraced the agency's newly more pessimistic conclusions in public.

"To the extent that we have regarded the Saudis as a deus ex machina, we have been in erro," Schiesinger said during a recent press conference. At the time he said the Saudis could be counted on to increase production to 12 millions barrels a day by the early 1980s - less than was earlier thought.

Schlesinger went on to say, however, that the oi-rich kingdom had the pootential to increase production to up to 20 million barrels, but that other factors weighed against it.

The eddies of skepticism in government and oil companies center on the technical basis for the agency's conclusions, and on repeated suggestions that the administration is deploying the downgraded Saudi oil numbers ti prod Congress into enacting the Carter energy plan now deadlocked in the Senate.

Officials from some of the four Aramco parent companies, Exxon, Texaco, Mobil and Standard Oil of California, as well as Aramco vice president James V. Knight disagree with CIA's 8.8-million-barrel-a-day assessment.

"We know of no basis on which they are doing that," says Knight. He maintains that Aramco could go to more than 10 million barrels on any given day.

Government officials familiar with the CIA study have said they question the CIA's interpretation of oil field data. "From what I can tell, the CIA does not have the expertise," says one.

The most severe critism, however, is the suggestion that the new projections have a political twist.

"The numbers from the CIA have domestic political consumption," says one government oil analyst.

He and other skeptics point to a CIA study released by the White House last April when the president's energy message was sent to Congress. That study projected that the Soviet Union would be exporting 3.5 million barrels of oil a day by the mid-1980s. The study has sinced been disavowed by a number of experts, including Schlesinger, who privately says he does not agree with its conclusions.