U.S. oil prices gained 1.82 percent on Wednesday on a decrease of crude oil stockpiles in the United States and the weakening of U.S. dollar.

Commercial crude oil stockpiles in the United States dropped 2.1 million barrels in the past week ending Sept. 14 to the lowest level since February 2015, according to a report issued by the U.S. Energy Information Administration on Wednesday.

Moreover, the dollar index, which measures the greenback against six major peers, declined 0.11 percent in the afternoon session on Wednesday.

"An active support of such price developments or deliberate lack of countermeasures (no supply response) looks unlikely in the current political environment, and Trump's by now well-known aggressive foreign policy," said a report by JBC Energy issued on Wednesday.

Market players recently showed substantial concern over less crude oil supply from Iran and weaker-than-expected production expansion from Saudi Arabia.

The West Texas Intermediate (WTI) for October delivery increased 1.27 U.S. dollars to settle at 71.12 dollars a barrel on the New York Mercantile Exchange, while Brent oil for November delivery grew 0.47 percent to 79.4 dollars per barrel on the London ICE Futures Exchange.