Can you have too much of a good thing? Maybe so. Warren Buffett, though, doesn't seem to fully agree with that philosophy.

Buffett keeps buying one stock hand over fist for Berkshire Hathaway's (BRK.A -0.76%) (BRK.B -0.69%) portfolio. Yesterday, Berkshire revealed via a regulatory filing that it invested an additional $122.1 million in Occidental Petroleum (OXY -0.15%) over a three-day period.

Buffett's buying spree includes Occidental shares

The latest purchase means Berkshire's stake in Occidental now exceeds 25% of all outstanding shares. The oil stock ranks as the sixth-largest holding in Berkshire's portfolio. But that wasn't always the case. 

Buffett first began buying Occidental in early March 2022, starting off with 29.8 million shares. It didn't take long for Berkshire's stake to grow considerably. By the end of the month, the conglomerate owned more than 136.4 million shares of Occidental. 

Beginning in May 2022, the legendary investor added to Berkshire's position in Occidental for five consecutive months. After a temporary pause, Buffett resumed his purchases in March 2023. So far this year, Berkshire had added nearly 30 million shares. 

This isn't the first go-round with Occidental for Buffett. Berkshire also initiated a position in the stock in the third quarter of 2019. However, by the second quarter of 2020, Buffett had sold all of Berkshire's shares in the oil company.

More to come (probably)

Could history repeat itself, with Berkshire again exiting its Occidental position soon? Maybe, but I don't think so. Instead, I look for Buffett to keep buying more shares.

There's one especially important indication that Buffett has more than just a passing interest in Occidental. In August 2022, Berkshire obtained approval from the Federal Energy Regulatory Commission (FERC) to acquire up to 50% of the company. That federal approval doesn't require Berkshire to buy any shares of Occidental. However, the conglomerate probably wouldn't have gone to the trouble of seeking the FERC blessing if Buffett didn't plan to significantly increase Berkshire's stake.

Buffett clearly likes Occidental's management. He told CNBC earlier this year that Occidental CEO Vicki Hollub is "extremely competent." The legendary investor also seemed to be optimistic about the company's prospects over the coming years. 

Don't expect Berkshire to completely take over Occidental, though. Buffett said at Berkshire's annual shareholder meeting in May, "There's speculation about us buying control, we're not going to buy control." He added, "We wouldn't know what to do with it." 

Is Occidental a good pick?

Investors shouldn't buy shares of Occidental just because Buffett is. But is the oil stock a good pick right now? I believe it is. For one thing, I agree with Buffett about Occidental's management team. Betting on the jockey isn't just a good strategy for horse racing -- investors should keep it in mind, too.

Occidental's valuation is also attractive. The stock trades at a forward price-to-earnings ratio of around 11. While that's roughly in line with the overall oil and gas industry, it's well below the valuation of the S&P 500. 

The demand for oil and gas should increase over the coming years, despite the push to reduce carbon emissions. That effort could also present a huge opportunity for Occidental. The company is investing heavily in carbon capture and sequestration, especially direct air capture facilities that suck carbon out of the air.

It certainly doesn't hurt that Buffett keeps buying Occidental. The more he sees the stock as a good thing, the better it will be for shareholders who aren't multibillionaires.