Embattled oil and gas supermajor Exxon Mobil Corp. topped Citadel Advisors LLC's list of biggest energy and utilities sector holdings at the end of the third quarter of 2020 after the fund manager added nearly 6.5 million shares to its position in the company.

Citadel's 0.2% stake in Exxon was valued at just $246 million as of Sept. 30, according to the fund manager's latest Form 13F filing. The driller, which was the world's biggest company in 2011, exited the Dow Jones Industrial Average index in August and posted a third-straight quarterly earnings loss for the third quarter as it continued to reel from the oil price crash. Exxon also warned it could write down up to $30 billion in natural gas holdings in the U.S. and Canada, with one industry analyst recently calling the firm "trapped given that they are cutting costs and [capital expenditures] as hard as possible."

Citadel's total energy and utilities portfolio, meanwhile, rose nearly 33% from $3.24 billion to $4.31 billion at the end of the previous quarter.

The fund manager's top buy by the number of shares during the third quarter was independent oil and gas producer Noble Energy Inc., which Chevron Corp. acquired Oct. 5 for $12.82 billion. That list also included U.S. shale drillers Apache Corp., Antero Resources Corp. and Southwestern Energy Co., as well as Occidental Petroleum Corp.

Citadel added 43 new energy and utilities stocks to its portfolio, with a 0.2% stake in utility Dominion Energy Inc. worth $121.2 million as the biggest addition. The fund manager also invested in gas pipeline giant Williams Cos. Inc., which recently announced a goal of net-zero greenhouse gas emissions by 2050, and in oil producer Whiting Petroleum Corp., which emerged from Chapter 11 bankruptcy Sept. 1.

Citadel's biggest stake sale during the third quarter by the number of shares was 10.9 million positions in utility PG&E Corp., which shut off power to hundreds of thousands of customers in August when a heatwave prompted California's first rolling blackouts in almost 20 years.

The fund manager also slashed its stake in Marathon Oil Corp. by over 81% as the company's dividend remained suspended.

Citadel Advisors sold off its stakes in 69 energy and utilities companies. The largest exit was Eversource Energy, where the fund manager held a stake valued at $17.3 million on June 30.

Citadel also unloaded its positions in utilities Avangrid Inc. and Southern Co.