Norwegian oil firm Okea is looking at four options to develop its North Sea North Sea Grevling oil discovery, which in turn could impact on the company's valuation in a deal with Thai investor Bangchak Corporation PCL (BCP), it said on Tuesday.

BCP has agreed to invest 939 million Norwegian crowns ($112.25 million) in Okea to partly finance the company's 4.5 billion crowns acquisition of Royal Dutch Shell's stakes in the Draugen and Gjoea fields.

Okea, which plans to list on the Oslo stock market in the next 12 months, said the deal between BCP and Okea's majority owner, private equity firm Seacrest Capital, values the Norwegian oil firm at 860 million Norwegian crowns.

The valuation could fall, however, to 778 million crowns, or rise to 940 million, depending on whether or not the company is able to decide on a concept selection and a plan for development (PDO) before the initial public offering (IPO) takes place.

The various development options for Grevling included a stand-alone floating production, storage and offloading vessel (FPSO), as well as a subsea tie-in to an existing platform.

Okea also said it is considering installing a jack-up rig with a floating storage and offloading facility, or a wellhead platform, and that its aim is for a per-barrel break-even price below $35-40 when production starts in 2020-22.

Redeployment of a leased FPSO could allow it to bring the field onstream in 2020, but this would also be the most expensive option, the presentation showed.

Okea has a 55 percent stake in Grevling after selling 15 percent to UK's Chrysaor in March, while Norway's state-owned Petoro has 30 percent.

Chrysaor has an option to increase its stake to 35 percent in the discovery estimated to hold 16-51 million barrels of oil equivalents.

Okea also said Repsol's Yme field re-development project, where it holds a 15 percent stake, was on track to start production in the first quarter of 2020.

Yme's recoverable proven and probable reserves are estimated at around 66 million barrels of oil, based on a 10-year field lifetime, but the long-term ambition will be to produce 90 million barrels of oil, the presentation said.

($1 = 8.3651 Norwegian crowns)

(Reporting by Nerijus Adomaitis, editing by Terje Solsvik and Ed Osmond)