The Aoka Mizu floating production, storage and offloading (FPSO) vessel ordered by Hurricane Energy has left Dubai following a series of upgrades, the company said, another milestone for the group as it seeks to extract so-called fractured basement oil in Britain.

Hurricane specializes in recovering oil from fractures in hard and brittle rock known as fractured basement reservoirs, which some see as a risky way to obtain crude.

It expects first oil from its Greater Lancaster Area (GLA) project, west of Scotland's Shetland Islands, in the first half of 2019. Any progress towards that is closely watched by the market.

"The passage (for the FPSO) is around six weeks with the potential for hook-up and first oil before year-end. This is ahead of H1/19 guidance and our cash flow expectations," Royal Bank of Canada said in a note.

The Aoka Mizu has been undergoing repair, upgrade and life extension works at the Drydocks World Dubai shipyard and will sail to Rotterdam for completion before proceeding to the Lancaster field.

Together with its Greater Warwick Area (GWA) project, Hurricane aims to add net reserves of 750 million barrels to its portfolio.

In a coup for Hurricane, Spirit Energy, backed by Centrica, last month agreed to invest almost $400 million in exchange for 50 percent of Hurricane's GWA.

"The final stage of preparations at the (GLA) field was a program of rock dumping to protect subsea infrastructure, which has been successfully completed," Hurricane said.

There is currently no fractured basin field in production in Britain. Lundin Petroleum in August announced good productivity from a fractured reservoir in the Norwegian North Sea.

(Reporting by Shadia Nasralla; Editing by Dale Hudson)