ONEOK has struck a deal with EnLink Midstream to buy its remaining assets in the Permian for $4.3 billion in stock, boosting its presence in the star of the shale patch further amid growing expectations of a surge in natural gas demand. Earlier this year, the gas infrastructure operator acquired a 43% stake in EnLink Midstream, paying $3.3 billion for it. It also acquired a stake in another pipeline operator at the time, Medallion Midstream, for $2.6 billion. ONEOK is one of the largest energy infrastructure operators in North America. It has a…