S&P/ASX 200 Index (ASX: XJO) energy shares are grabbing investor attention on Monday. This follows another oil production hike announcement from the Organization of the Petroleum Exporting Countries and its allies (OPEC+) over the weekend.

During the Monday lunch hour, the ASX 200 is down 0.2%. Amid concerns of a medium-term global oil glut, the S&P/ASX 200 Energy Index (ASX: XEJ) is taking a sharper fall, down 0.4%.

But not all of the Aussie oil and gas companies are getting sold down.

Here's how the big ASX 200 energy shares are tracking at this same time:

• Woodside Energy Group Ltd (ASX: WDS) shares are up 0.5% at $22.35
• Santos Ltd (ASX: STO) shares are down 1.0% at $6.53
• Beach Energy Ltd (ASX: BPT) shares are down 1.1% at $1.33
• Karoon Energy Ltd (ASX: KAR) shares are down 0.8% at $1.63

So, what exactly is OPEC planning to do?

ASX 200 energy shares eyeing big oil price falls

The relatively resilient performance of the ASX 200 energy shares today comes amid an equally resilient oil price.

The Brent crude oil price is up 2.6% today at US$64.40 per barrel. Though, as we'll look at below, that may not last.

On Saturday, OPEC+ said it would add another 411,000 barrels of oil per day in production, commencing in July. This marks the third consecutive month of production increases for the cartel, which lifted output by a similar amount in May and June.

The increase sees OPEC+ more than halfway to restoring the 2.2 million barrels per day in production cuts it had instituted in recent years to help support the oil price. But as more oil hits the markets, ASX 200 energy shares have come under pressure.

Saudi Arabia is leading the drive. That's partly to please United States President Donald Trump, who's demanding cheaper oil prices, and partly to punish cartel members who have been producing more than their allotted quotas.

What are the experts saying?

Commenting on OPEC's announcement that could usher in lower oil prices and pressure ASX 200 energy shares, Jorge Leon, an analyst at Rystad Energy, said (quoted by Bloomberg), "OPEC+ isn't whispering anymore. May hinted, June spoke clearly, and July came with a megaphone."

Amrita Sen, director of research at Energy Aspects, added, "Fundamentals in the right-here, right-now are strong; inventories are very low. It is a good time for OPEC+ to add barrels to the market, so I don't see why they wouldn't."

But investors in ASX 200 energy shares may wish to take note of the new oil price forecast from JPMorgan Chase & Co.

The broker forecasts the Brent crude oil price will slide into the higher US$50 per barrel range in the latter months of 2025, expecting OPEC+ to add to a global oil oversupply of some 2 million barrels per day.