Brent crude was down 11 cents at $78.53 a barrel by 0137 GMT, after falling 0.6% on Wednesday. U.S. oil fell 5 cents to $74.78 a barrel, having also declined by 0.6% in the previous session.
U.S. oil and fuel stockpiles increased last week, the U.S. Energy Department's Energy Information Administration (EIA) said on Wednesday.
Crude inventories were up by 4.6 million barrels in the week to Sept. 24 to 418.5 million, EIA data showed, compared with analysts' expectations in a Reuters poll for a 1.7 million-barrel drop.
But both contracts tilted into higher territory earlier in the session. After two days of price losses, oil bulls may also be looking for the next barrier to breach after Brent rose above $80 for the first time in around three years on Tuesday.
"$80 oil is not over-the-top high," said Joseph Perry, an analyst at StoneX, said.
The rise in inventories came as production in the United States returned to around the levels they were at before Hurricane Ida hit about a month ago. Output rose to 11.1 million barrels per day last week.
On the production side, next week the Organization of the Petroleum Exporting Countries and its allies including Russia, a grouping known as OPEC+, are likely to maintain a deal on adding 400,000 barrels per day (bpd) to its output for November.
The power crisis and housing market concerns in China have hit sentiment recently because any fallout for the world's second-biggest economy would likely have meant a hit on oil demand, analysts have said.
China is the world's biggest crude importer and its second-largest user after the United States.