Wall Street is throwing the most money at U.S. energy companies since at least 2000 amid growing confidence that the industry is emerging from the worst downturn in a generation. Energy firms raised $6.64 billion in 13 equity offerings in January, drawn in by a rich combination of oil prices consistently above $50 a barrel and a rush to drill that’s doubled the rigs in use in the U.S. and Canada since May. The biggest change from last year: Oilfield servicers that provide the rigs, fracking equipment and sand used by drillers.