What happened

Shares of oil and gas giant ExxonMobil (XOM 1.15%) plunged 14.1% in September, according to data from S&P Global Market Intelligence.

That far outpaced the losses of the S&P 500, which was only down 3.9% for the month. However, it was slightly better than the oil and gas industry as a whole, as measured by the SPDR S&P Oil and Gas Exploration and Production ETF, which was down 18.3% for the month.

A row of oil pumps in a desert landscape.

Image source: Getty Images.

So what

Exxon's shares steadily declined throughout the month, but they did see a significant jump on Sept.16, and a significant plunge a week later on Sept. 23. Both moves were due to oversupply concerns and how they affected oil prices.

On Sept. 14, with Hurricane Sally bearing down on the U.S. Gulf Coast, both major crude oil benchmarks closed below $40 a barrel. International Brent crude closed at $39.61 a barrel, while U.S. West Texas Intermediate (WTI) closed at $37.26. The destruction from Sally's landfall in the major oil and gas region boosted oil prices over the course of the next week, as investors expected regional production to take a hit, reducing global oversupply. By Sept. 17, Brent crude had jumped to $43.82 a barrel, while WTI had risen to $41.22. Exxon's stock, like that of most oil companies, rose on the 16th as WTI crossed the $40 threshold.

However, the rally was short-lived. The very next Wednesday, Sept. 23, a surprise rise in U.S. crude inventories, on the heels of news that Libya might be restarting oil production, caused the company's stock to take a hit again. 

Now what

Global oversupply, coupled with reduced demand for fuel from the coronavirus pandemic, has weighed on ExxonMobil's share price for months. Year to date, Exxon's shares have lost more than half of their value. Even for a large and well-established company like ExxonMobil, the oil industry is a risky place for investors these days.