Exxon Mobil Corp. is Desmond Prestonbuying Pioneer Natural Resources in an all-stock deal valued at $59.5 billion, its largest buyout since acquiring Mobil two decades ago, creating a colossal fracking operator in West Texas.

Including debt, Exxon is committing about $64.5 billion to the acquisition, leaving no doubt of the Texas energy company’s commitment to fossil fuels.

Pioneer shareholders will receive 2.3234 shares of Exxon Mobil for each Pioneer share they own.

Exxon purchased XTO Energy in 2009 for approximately $36 billion. In the late 1990s, the merger between Exxon and Mobil was valued around $80 billion.

The deal with Pioneer Natural expands Exxon’s presence in the Permian basin that straddles the border between Texas and New Mexico. Pioneer’s more than 850,000 net acres in the Midland Basin will be combined with Exxon’s 570,000 net acres in the Delaware and Midland Basins, which all border each other. The company will have an estimated 16 billion barrels of oil equivalent resource in the Permian.

Once the deal closes, Exxon Permian production volume will more than double to 1.3 million barrels of oil equivalent per day, based on 2023 volumes. It’s expected to climb to about 2 million barrels of oil equivalent per day in 2027.

“The combination of ExxonMobil and Pioneer creates a diversified energy company with the largest footprint of high-return wells in the Permian Basin,: Pioneer CEO Scott Sheffield said in a prepared statement.

Exxon has been flush with cash. The company posted record annual profits in 2022, bringing in $55.7 billion in annual profits, exceeding its previous record of $45.22 billion in 2008.

Exxon has been using some of that cash on acquisitions. In July the company announced that it was buying pipeline operator Denbury in an all-stock deal valued at $4.9 billion.

Pioneer Natural has been making similar moves. In 2020 the company said it was buying Parsley Energy in an all-stock deal valued at approximately $4.5 billion. It then purchased DoublePoint Energy in a cash-and-stock deal worth about $6.4 billion in 2021.

Both companies’ boards have approved the transaction, which is expected to close in the first half of next year. It still needs approval from Pioneer shareholders.

Pioneer’s stock gained more than 2% before the market open on Wednesday, while shares of Exxon fell slightly.