Less than three years ago, Kan-based Tallgrass Energy accepted a $4 billion investor buyout led by Blackstone that took the midstream company private. A name change to simply “Tallgrass,” and appointment of a new CEO quickly followed, along with a fresh strategy to diversify the business from an oil-and-gas pipeline transporter and processor, to an infrastructure company with an eye on new-energy frontiers. ...

Let’s say you’re the UK’s largest oil and gas producer recording 208 MBOED in global volumes of which 90% is from the North Sea. Last year you posted $2.4 billion in profits. But along came a new windfall tax and, suddenly, that $2.4 billion in profits just became $8 million. ...