Energy stocks declined pre-bell Monday with the Energy Select Sector SPDR Fund (XLE) 1.4% lower recently.

The United States Oil Fund (USO) was down 1.9% and the United States Natural Gas Fund (UNG) was 0.9% lower.

Front-month US West Texas Intermediate crude oil was down 1.6% at $57.36 per barrel at the New York Mercantile Exchange. Global benchmark North Sea Brent crude oil lost 1.4% to $60.42 per barrel. Natural gas futures were 1.6% higher at $4.012 per 1 million British Thermal Units.

Shell (SHEL) has been discussing with advisers to assess a potential acquisition of BP (BP) in recent weeks, Bloomberg reported, citing unnamed sources familiar with the matter. BP shares advanced by almost 3%, while Shell shares were down more than 1% premarket.

Sunoco (SUN) shares were over 2% lower after the company said it has agreed to acquire all outstanding shares of Parkland for approximately $9.1 billion in cash, equity, and assumed debt.

Comstock Resources (CRK) announced a dual listing of its shares on NYSE Texas, a new equities exchange headquartered in Dallas. Shares of Comstock Resources were down more than 2% premarket.