Crude oil prices were flat at the start of the trading day Thursday, as supply-side pressures balance against signs of renewed life in the Chinese economy.

Oil prices are wrapping up a volatile week, with wild swings putting the global benchmark Brent back above the $50 per barrel psychological threshold earlier this week. Prices plummeted Wednesday after U.S. data showed crude oil inventories continued to grow amid signs of tepid economic growth.

A series of signs that China was on its way to prolonged contraction added downward pressure to crude oil prices for most of the latter part of 2015. The Shanghai Composite Index closed up 1.83 percent in Thursday trading after service-sector data showed signs of recovery. That's mixed, however, as manufacturing data revealed signs of contraction earlier this week.

Brent crude oil was relatively unchanged in early Thursday trading at $48.55 per barrel. West Texas Intermediate, the U.S. benchmark price for crude oil, was steady at $46.31 per barrel.

Oil prices are down as weak economic momentum leaves demand for energy products lower. Data released late Wednesday from the U.S. Energy Information Administration show crude oil inventories at around 482 million barrels, the highest they've been in at least 80 years.

U.S. Federal Reserve Chair Janet Yellen testified on Capitol Hill, signaling there may be an interest rate increase announced in December, though it would be a slow implementation.

There are signs for improvement in the U.S. economy, she said, but more work remains to be done and the work of the Federal Reserve "is not complete."

The U.S. Bureau of Economic Analysis last week reported gross domestic product in the United States increased at an annual rate in the third quarter by 1.5 percent, compared with a 3.9 percent increase in GDP during the second quarter.