(Adds analyst, debt and liabilities estimate)
OSLO, Aug 24 (Reuters) - Offshore drilling contractor Seadrill plans to launch a long-awaited Chapter 11 debt restructuring by Sept. 12, and aims to raise $1 billion in new capital, it said on Thursday.
Once the biggest offshore rig firm by market value and the crown jewel of Norwegian billionaire John Fredriksen's business empire, Seadrill shares have plunged 99 percent from a 2013 peak as energy firms have slashed spending to cope with lower prices.
The Chapter 11 process provides a company with protection from creditors while it seeks to renegotiate its debts and secure its future.
"Our primary objective at the moment is concluding final negotiations on our comprehensive restructuring plan, which is at an advanced stage and likely to be implemented via Chapter 11 proceedings on or before 12th September 2017," Seadrill's Chief Executive Anton Dibowitz said in a statement.
The company has postponed a number of deadlines for debt restructuring, but some analysts believe this time could be different.
"What makes it different this time is that they have a one billion dollar bond maturing in September. That makes it (Chapter 11 restructuring) far more likely," Thomas Larsen, an analyst at Norway's largest bank DNB, said.
Larsen estimates Seadrill's total debt and liabilities, including about $2 billion to shipyards, at more than $10 billion.
Net interest bearing debt alone stood at almost $8 billion at the end of the second quarter, the company said.
Seadrill said the restructuring plan was likely to involve raising about a billion dollars of new capital, as well as a five-year extension of its bank facilities and "substantial" impairment or conversion of its bonds into equity.
Other stakeholders, including shipyards, will have to take some pain as well.
"As a result, the company currently expects that shareholders are likely to receive minimal or no recovery for their existing shares," the company said.
Larsen said he doubted anybody would put more equity into the company, so the capital would have to be raised via debt.
"It's difficult to say how much Fredriksen would contribute, but we think that he would probably contribute through some debt instrument," he added.
Seadrill said its business operations remained unaffected by the restructuring efforts, and it was able to re-contract a number of its rigs during the second quarter, reporting higher than expected quarterly revenues. (Reporting by Nerijus Adomaitis, editing by Terje Solsvik and Mark Potter)