Seeking to expand its resources in shale gas, Chevron Corporation has a definitive agreement to acquire independent natural gas producer Atlas Energy for $4.3 billion.

The San Ramon, Calif.-based energy giant has offered $3.2 billion in cash to the shareholders of Atlas, which is based in Moon Township, Pa. Atlas Energy stockholders would receive total consideration of $43.34 per share, a 37 percent premium over the Nov. 8 closing price. However, at least one shareholder has sued to block the deal, alleging that the price is too low.