Exxon Mobil Corporation (XOM) - Get Report shares slumped lower Wednesday after the biggest U.S. oil company warned investors that lower crude prices would clip its quarterly profits.

Exxon said late Tuesday in a Securities and Exchange Commission filing that overall profits in the three months ending in September would fall by around 50% from the same period last year to around $3.1 billion. Exxon's oil and gas production division would see a 45% slump from last year's $4.23 billion total, the company said, while downstream profits will likely tumble 70% to $500 million.

Exxon will publish its formal third quarter earnings on October 31.

West Texas intermediate crude prices have fallen some 8.5% over the third quarter of this year, as investors trimmed bets on increased demand amid the protracted U.S.-China trade dispute and factored in record domestic output from shale deposits in the Permian basin. 

Crude is also some 27% lower than it was last year, when the global economy was still humming along under the steam of both U.S. and China growth, and the impact of OPEC's 1.2 million barrels per day in production cuts were supporting world markets.

Exxon shares were marked 1.6% lower at the start of trading Wednesday to change hands at $67.87 each, a move that tips the stock back into negative territory for the year.

Exxon posted second quarter earnings of 73 cents per share earlier this summer, down 20.6% from the same period last year but just ahead of the Street consensus forecast as group revenues slipped 6% to just over $69 billion.

Exxon said its overall oil equivalent production rose 7% from last year to the equivalent of 3.9 million barrels of oil per day, as liquids productions in the shale-rich Permian basin grew 8% and natural gas volumes rose 5%.