Shares of Pioneer Natural Resources (PXD) jumped 10.5% on Friday, making it the best-performing stock in the S&P 500, following reports Exxon Mobil (XOM) is in advanced talks to purchase the shale driller for $60 billion.

At that price, it would be Exxon Mobil’s biggest acquisition since it was known simply as Exxon and bought Mobil Oil for $81 billion in 1999.

Reports indicated a deal could be finalized in the next few days, although there’s no guarantee the two sides will come to an agreement.

Adding Pioneer would help Exxon Mobil expand its presence in the Permian Basin of western Texas and southeastern New Mexico, the most prolific oil-producing region in the Western Hemisphere. Pioneer is the third-biggest producer there, behind Chevron (CVX) and ConocoPhillips (COP).

The news lifted shares of Pioneer Natural Resources into positive territory for the year. Exxon Mobil shares fell 1.7% on Friday.