Sergei Tyumenev stands on an oil rig in the middle of the flat swampland of western Siberia, 1,400 miles east of Moscow and 350 miles south of the Arctic Circle.

He can see a snowy expanse covered with scrub pine and stands of birch trees. Clustered around the 150-foot-high rig are the men's sleeping huts, a canteen, a bath, an outhouse and stacks of drilling pipe. The rig gently shudders and creaks as the drill slowly bores into the ground.Thirty years ago, this stretch of taiga was undeveloped wilderness inhabited mainly by the native Khanty-Mansiyski. Surgut was an outpost of 25,000 people, mainly Russians. But in 1965, the Soviet Union began drilling the vast reserves of oil in this region. Today, Surgut's population is 250,000, and the city has the raw, muddy feel of a frontier town. The Khanty- Mansiyski have been pushed to the north.

The Tyumen region, an area about one-fifth the size of the United States, yields 3 billion barrels of oil a year, or 8 million barrels a day - more crude oil than is produced by the United States.

On this day, Mr. Tyumenev and a handful of men are drilling a 9,514-foot- dee p well. The temperature is a balmy 38 degrees. April and May are the men's favorite months on the rigs: In the winter, temperatures can hit 40 or 50 below, and in the summer, clouds of mosquitoes torment the drillers.

Mr. Tyumenev, who oversees the drilling, and three roughnecks swing into action to add another 78-foot length of drill pipe.

In a blur of movement, the men unscrew the pipes and wrestle new ones into place. Gray-brown drilling fluid and mud fly, and the men are covered in dirt

from their hard hats to their boots.

"We work under these difficult conditions, and we just don't see what we get in return," said Volodya Khoroshavin, 34. "We are just getting by. We get a good salary, but there's almost nothing to buy. Furniture, decent clothes - it's almost impossible to find. It would be a lot better if we had our independence, if we could keep some of our profits. Then people would be a lot more interested in the results of their work."

"We see on television now how you live in America, and we want to live that way, too," said Renat Baodinov, 26. Asked what he imagined when he pictured the United States, Mr. Baodinov thought for a moment and then replied, "You have everything there. It is of good quality. And you don't have to wait in line for it."

Mr. Tyumenev retires with a geologist to a small truck, from which they send down the hole a device that tells them the depth and direction of the drilling. American equipment would allow them to drill and measure at the same time, but here, using technology from the 1960s and '70s, they must stop the drilling and run the measuring device down the hole, wasting hours.

The geologist repeatedly flips a switch on a small, gray metal box with jury-rigged wiring. It looks like it was made in somebody's basement. ''This," he says with a wink, "is our computer."

Mr. Tyumenev came to this area from Moscow seven years ago because, as he says, it was "a place with a future." There was the chance to earn as much as 1,000 rubles, or $1,600, a month, compared with the $250 the average Soviet worker takes home. But as the amount of goods on the shelves has dwindled in the years of perestroika, he and his wife have become more discouraged.

For thousands of people in Surgut, and tens of thousands in western Siberia, life is even tougher. They live in wooden shacks, known as bolki, or small metal sheds, known as vagonchiki. There are numerous such shantytowns in and around Surgut where thousands of workers' families live without running water or indoor plumbing.

Winter snow piles up to the roofs of the sheds, and when it melts in April and May, great pools of water form in the bolki communities. The city doesn't pick up garbage in the shantytowns, leaving people to dump their trash in and around the shacks. At nighttime, snarling dogs menace passersby.

As far as Mr. Tyumenev is concerned, the way out is a market system that will give freedom, and responsibility, to the oil workers.