Brent crude oil futures rose slightly after banks tapped the European Central Bank for 529 billion euros, on Wednesday, in the ECB's three-year refinancing operation, beating expectations, and spurring hopes that the stimulus would boost buying of risky assets, like oil.April Brent crude on London's ICE Futures exchange rising 7 cents, to 122.76 dollars a barrel, after the announcement. On the New York Mercantile Exchange, light, sweet crude futures for delivery in April rose 67 cents, at 107.22 dollars a barrel.