Kidnappings of foreign oil workers have become commonplace in Nigeria, with dozens taken during the last three weeks alone.
Hostages are usually treated well and returned safely, but the authorities often have no way of knowing if their captors are politically or financially motivated.
"There has been one Transocean sub-contractor taken from the Trident 8 rig. There are another 23 people on the rig and they are all safe," said Transocean spokesman Guy Cantwell.
Militant groups in Nigeria's oil rich Niger Delta region are campaigning for greater wealth distribution and more autonomy.
Nigeria is the world's eighth largest exporter of oil.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.