The clean-out work has been completed at the first well, 9-21, and the rig has now moved onto the next well.
Following the clean-out operations at each well there will be a flow test, though the results won’t be released until all five have been completed - which is expected in early January.
"We are delighted that operations have commenced and look forward to updating shareholders on our progress in due course," said Stephen Schoepfer, Curzon managing director.
The Coos Bay coal bed methane project spans some 45,000 acres in Oregon and is estimated to host 273bln cubic feet of contingent resources.
Phase 1 of development includes five low-cost workovers and the drilling of two new wells and the programme is expected to be completed in the second quarter of 2018.