Shares of Tallgrass jumped more than 35% percent on Wednesday, bringing the stock price close to the level offered as part of the deal. Blackstone is offering to buy the rest of Tallgrass' Class A stock for $19.50 per share in cash.
The investment firm already has a large stake in the energy company, holding 44% of its outstanding equity. The offer represents a 35.9% premium over its closing share price on Tuesday.
Tallgrass is a midstream energy company that operates pipelines for crude oil and natural gas. For its most recent quarter, which ended June 30, Tallgrass reported $211 million in revenues.
Tallgrass shares have struggled recently. The stock fell by more than 30% between July 12 and the market close on Tuesday. The Kansas-based company has a market cap of roughly $5.5 billion.
Shares of Blackstone were down less than 0.1% on Wednesday.
According to offer letter, the proposed deal would be structured as a merger between Tallgrass and an acquisition vehicle created by Blackstone. The deal would be made through Blackstone's infrastructure group.