Oil companies in the Gulf of Mexico had by Thursday night U.K. time evacuated 13 platforms and five drill rigs, as Hurricane Dean builds in strength in the wake of Tropical Storm Erin.

While, Erin forced the shut-in of some oil and gas wells, the threat of Dean forced the evacuation of 1.6 percent of the 834 platforms and five percent of the 100 rigs in the Gulf of Mexico, according to a survey by the U.S. Minerals Management Service.

Just 2,563 barrels per day of the Gulf’s 1.3 million bpd of oil production has been shut in. Some 10.5 million cubic feet per day of gas of the Gulf’s 7.7 bcm/d is hemmed in.

During Hurricanes Katrina and Rita, the shut-in valves functioned 100 percent of the time, the MMS reported.