Richmond lawyer Wyatt B. Durrette claimed yesterday he had captured enough delegates to win the Republican nomination for governor of Virginia.

Though Durrette stopped short of proclaiming himself victorious over Rep. Stan Parris, he said Tuesday night's mass meetings in Fairfax County gave him a slim margin of victory.

"We only needed 232 more delegates to be nominated . . . . We won at least 240 and probably more," Durrette said at a morning news conference in Richmond.

Donald Huffman, state chairman of the Republican Party, said that while Durrette may be slightly overestimating his lead, it would be difficult for Parris to overtake him.

"It certainly appears from the Fairfax County votes that Durrette has a commanding lead," Huffman said. "It would be very difficult but not impossible for Mr. Parris to overcome it."

Only a fourth of the delegates to the state's nominating convention May 31 and June 1 in Norfolk remain to be selected. The GOP nominee is expected to face Democrat Gerald L. Baliles, who this week apparently secured his party's nomination after a series of party caucuses across the state.

Parris' campaign cochairman, William Stanhagen, disputed Durrette's delegate counts. "I'm sure we can still win," Stanhagen said. "We'll come down to a nose-to-nose horse race going into the convention."

Stanhagen said Parris' figures show the congressman only 200 votes behind Durrette statewide. While he conceded that Parris failed in a tactical maneuver that could have given him all Fairfax County's 526 votes, he said Parris won the majority, and accused Durrette's campaign of "quite a little orchestration of the figures."

Durrette, who represented Northern Fairfax for six years in the General Assembly, replied that Parris' numbers were "fictitious."

The Durrette staff conceded that Parris carried the four Fairfax magisterial districts that are in the congressman's district and won about half the county's delegates. But Mike Conlin, Durrette's campaign manager, said, "Stan needed to do a whole lot better than that. It wasn't enough for him to break even. He had to wipe us out."

Durrette, who narrowly lost two previous bids for statewide office, has shied away from declaring himself the victor in the race, even while saying he had enough votes to win. At a celebration party late Tuesday night in Springfield, he warned supporters: "Don't count your chickens."

Conlin said Durrette does not want his supporters to become overconfident and fail to turn out for the remaining mass meetings or at the state convention in Norfolk.

As a practical matter, however, Conlin said Parris is out of the race. "He would virtually have to win every vote that's out there, plus all the uncommitted, and take away some votes from us," Conlin said. "He can't do that."

"It's over," said Mason District Supervisor Thomas M. Davis III, who worked for Durrette in Fairfax County. "There's no question about it. Parris is the only guy in the state who thinks he's still in the running."

Baliles, who won the office of state attorney general by beating Durrette by 27,000 in 1981, said this week he has defeated his Democratic opponent, Lt. Gov. Richard J. Davis. Like Parris, Davis has vowed to stay in the race.

Baliles' apparent victory disappointed many Republicans, who saw Davis as the weaker opponent, but Durrette said yesterday he saw no real difference between the two Democrats.

He attributed his 1981 loss to Baliles to the fact that he was at the bottom of a losing and troubled Republican ticket while Baliles was aided by the popularity of Charles S. Robb, the Democratic candidate for governor.

"That was very different circumstances for me," Durrette said. "It was very difficult at the bottom of the ticket."

This year's race for the Republican nomination for lieutenant governor engendered far less consensus on who is ahead than the Durrette-Parris contest.

Former attorney general J. Marshall Coleman of McLean said yesterday he won nearly 400 of the 526 Fairfax votes and is only 250 shy of the number needed for his party's nomination. "We're very close to the number of delegate votes needed for a first ballot victory at the convention," Coleman said.

Richard A. Viguerie, a leading advocate of the New Right movement, said he won 233 of the Fairfax votes and achieved the major victory in his home Fairfax base needed to boost his sagging campaign.

"We're right where we wanted to be," said Viguerie campaign manager Tim Gresham. "Right on Marshall Coleman's trail."

Aides to a third candidate, state Sen. John H. Chichester of Fredericksburg, also disputed Coleman's totals. Dennis Peterson, Chichester's campaign manager, said his count shows that Coleman captured barely half the Fairfax vote. He said the rest was divided among the uncommitted delegates, Chichester, Viguerie and the two other candidates, lobbyist Maurice Dawkins of Springfield and state Del. A. R. (Pete) Giesen of Augusta County.

He said Chichester, who was not expected to do well in Fairfax, racked up about 70 votes.