U.S. stock index futures rose on Friday after Nike and Oracle reported higher-than-expected financial results, but trading was likely to be volatile as equity derivative contracts expired.

Shares of Nike Inc, the world's largest athletic shoe and apparel maker, rose 4.3 percent in Europe after it posted stronger-than-expected quarterly net profit with help from a tax benefit and weak dollar.

Oracle Corp's shares rose 0.9 percent in Europe after its earnings and revenue topped analysts' estimates and Citigroup raised its price target on the world's third-largest software maker to $25 from $24.

But volatility is expected to intensify due to the expiration of four different equity options and futures contracts, a quarterly event known as quadruple witching. The phenomenon can create sudden spikes and dips in the market and volume as some investors exercise their derivative positions or roll them forward at the last minute.

It's options expiration today, which means higher volatility and swelling volume. And we have some good corporate news, said Peter Cardillo, chief market economist at Avalon Partners in New York.

While the economic calendar is thin, the market is likely to keep a close eye on speeches by a number of Federal Reserve officials, he added.

S&P 500 futures were up 7.8 points, above fair value, a mathematical formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract.

Dow Jones industrial average futures were up 65 points, and Nasdaq 100 futures rose 11 points.

U.S. stocks fell on Thursday as a weakened dollar and a surge in oil prices kindled fresh concerns about inflation, snuffing out a two-day rally that followed the Federal Reserve's deep interest-rate cut.

And inflation fears are likely to continue to nag on Friday, as the dollar fell to an all-time low against the euro. Investors dumped the greenback after the Fed's interest rate cut on Tuesday, which makes returns on the currency less rewarding.

While a weakening dollar can give a lift to shares of companies that are big exporters, it also threatens to make inflation worse because of the United States' heavy reliance on imported goods.

But oil prices slipped a little, with U.S. crude for November delivery down 12 cents at $81.66 a barrel.

NIKE Inc Investment U.S.