The company said it had also reduced to 30 days its commitment with the semisub Kan Tan 4 from late 2010.
"Both arrangements allow better management of drilling and mobilisation-demobilisation costs, as well as reducing risk exposures," said Roc.
The other party in the swap is Shell, which will get the Songa Venus for immediate use for 168 days.
When Roc is finished with the Ocean Patriot in late September this year, the rig will start a two-year term with Apache.
