Energy stocks were leaning lower premarket Monday, with the State Street Energy Select Sector SPDR ETF (XLE) down 0.1%.

The United States Oil Fund (USO) was 0.4% lower and the United States Natural Gas Fund (UNG) was down 7.3%.

Front-month US West Texas Intermediate crude oil was down 0.4% at $63.31 per barrel at the New York Mercantile Exchange. Global benchmark North Sea Brent crude oil lost 0.3% to $67.84 per barrel, and natural gas futures were 7.8% lower at $3.16 per 1 million British Thermal Units.

Transocean (RIG) has agreed to acquire Valaris (VAL) in an all-stock transaction valued at around $5.8 billion, the companies said. Shares of Transocean were down more than 3% premarket, while Valaris stock was up more than 19%.