The costs of the Corrib gas project are set to top €3.6bn in 2015 when gas is finally expected to flow from the field.
The Corrib partners have spent an additional €340m on various aspects of the project this year and next year anticipate that a further €250m will be spent.
This follows an outlay of €330m in 2013, bringing the total projected spend over the three-year period to €920m.
This will result in the costs for the entire project topping €3.6bn - more than four times the original estimate of €800m.
Gas was originally expected to flow from the field in 2003.
The project is now 12 years behind the original schedule.
However, a spokesman for Shell Ireland said yesterday that the Corrib development has made good progress during 2014, that included completion of the 5km tunnel to bring gas ashore.
The works include completion of piping and umbilical testing in the tunnel.
He said that offshore in 2014, all wells were tested and are ready to commence production in 2015. "We expect approximately 800 staff to be employed at first gas," the spokesman said.
"Once all construction is finalised and reinstatement is complete, Corrib will sustain 175 high quality long-term jobs for the next 15 to 20 years."
The spokesman was commenting on new accounts just filed by Shell E&P Ireland Ltd (SEPI) for 2013 showing that the firm recorded a pre-tax loss of €28.5m and this followed a pre-tax loss of €23.7m in 2012.
The Corrib development is Ireland's largest ever energy investment and more than 6,000 people will have worked on bringing Corrib gas to market with the project maintaining 1,250 full-time jobs in Mayo, Donegal and Dublin since 2004.
Staff costs last year rose 17pc from €18.38m to €21.59m.
Emoluments for the firm's three directors, including managing director Michael Crothers, rose from €1.4m to €2.17m.
A tax credit of €6.4m reduced the loss to €22m and last year's tax credit brings to €120m Shell Ireland has received in tax credits since the project's inception.
Shell Ireland's shareholder funds last year topped €1.4bn after a further cash injection of €180m.
Shell has a 45pc share with Statoil having a 36.5pc share and Canadian-owned Vermilion owning 18.5pc.