SAN FRANCISCO (AP) _ Chevron Corp. appears to be on a fast track toward developing the huge Tengiz oil field in a joint venture with the Soviet government, but it faces a long road before the deal is complete, analysts said Monday.

Chevron has agreed with the Soviet Ministry of Oil and Gas Industry to study the feasibility of developing the field, with reserves estimated at more than 25 billion barrels - about 2 1/2 times those of Alaska's Prudhoe Bay.

The ''protocol of intentions'' agreement signed Saturday is the first step toward an eventual joint venture to extract the oil.

But long negotiations are expected before any joint venture agreement is reached. Complicating the dealmaking are the tangled Soviet bureaucracy and a history of questionable success. Even in cases where joint venture agreements formally are reached, only 15 percent actually go into operation.

Nevertheless, the Soviets appear highly motivated to ensure that the Tengiz development and similar projects actually occur. The Soviet Union is the world's biggest oil producer, but production has fallen in recent years, and U.S. technology and capital are needed to reverse that trend, said Warren M. Shimmerlik, a senior oil analyst for County NatWest USA in New York.

''It's clear that this is a huge resource,'' Shimmerlik said. ''And this is the kind of asset that if opened up to the West could be very significant.''

However, he said, success is years away. Furthermore, while Chevron may expect to make a profit, it's unlikely to get a windfall.

''They will negotiate a reasonable deal,'' Shimmerlik said. ''The Soviets want this work done, and both sides will benefit from it.''

Eugene Nowak, who heads the energy group at Dean Witter Reynolds Inc., noted that the protocol is just a first step in what could become a significant project for Chevron. He said there appeared to be no way Chevron could lose - the worst that could happen is nothing, Nowak said.

''Based on what company officials are saying about the timetable, Chevron appears to be on a rather fast track,'' Nowak said.

''The uncertainty is that this is a new venture for the Soviets, and it's the business side that's questionable rather than the technical side,'' Nowak said.

Shimmerlik said he expects the Soviets ultimately to allow several more companies into similar projects.

''There will be plenty of companies doing this, and it's a question of who winds up with the best properties,'' he said.