A helicopter ferrying an injured oil worker from an offshore drilling rig in West Africa’s Gulf of Guinea was missing Monday with an American and three Nigerians onboard, ChevronTexaco’s Nigerian affiliate said. The helicopter disappeared five minutes after it took off Monday afternoon from the Sedco Energy platform off Nigeria’s southern coastline, said ChevronTexaco spokesman Sola Omole, speaking from the commercial capital of Lagos. The four people onboard the helicopter were the American pilot and three Nigerians — the co-pilot, the injured oil worker and a medical worker — the latter two employed by the oil contract firm Transocean Inc., which owns the Sedco platform.Full Story