Much of the growth in offshore exploration and production is expected from Nigeria and Angola, a report from the U.S. federal government said. Oil field services company Baker Hughes reported 31 rigs actively exploring for or producing natural gas in U.S. waters for the week ending Sept. 18. That’s down by half from the same week last year. A daily brief from the U.S. Energy Information Administration said the Gulf of Mexico’s share in the global offshore rig mix has declined from about half the world total in 2000 to less than 20 percent in the years since 2008. “Most of the more recent growth in active offshore rigs outside the United States has occurred in Africa. […]