Business Insider reports a surprise increase in American oil stockpiles ratcheted up fears of a global recession.
Futures fell as much as 5.8% to a seven-month low on Wednesday.
That pushed oil into bear market territory.
Having extra supply dilutes prices, exacerbated by investors' worries that demand may slow.
US-China trade tensions have overtaken threats of supply disruption in the Persian Gulf as the biggest headwind to oil.