SINGAPORE, Aug 29 (Reuters) - U.S. crude oil futures surged more than $4 in opening trade on Monday, hitting a new record high above $70 a barrel after Hurricane Katrina forced Gulf of Mexico producers to shut in more than a third of their output. Katrina, which strengthened into a rare, maximum power Category 5 hurricane as it spun through key oil and gas fields toward New Orleans, shut in a total 633,000 barrels per day (bpd), according to company figures on Sunday. It also forced the closure of seven refineries and a major U.S. crude import terminal. Crude oil...