Iraq's Majnoon oilfield should be ready to produce 175,000 barrels per day (bpd) by the end of 2012, triggering cost recovery and service fee payments.
Iraqi officials say the field could even reach that output, from current production of around 54,000 bpd, by August, depending on pipeline infrastructure, completed wells and also visa delays for foreign contractors.
Three rigs are working at Majnoon, which hit as high as 90,000 bpd output in December 2010, but work on a de-gassing station has temporarily reduced production.
Shell and its minority partner Petronas of Malaysia, are targetting production of 1.8 million bpd by 2017.
Ole Myklestad, Shell's manager at Majnoon, told Reuters on Tuesday that they had spent around $1 billion since taking over the field in 2010, and planned to invest another $1 billion this year alone. Total spending over the 20-year life of the project would be around $50 billion.
Mine clearance had required more effort than originally planned, with $30 million spent on it so far, and another $20 million planned this year.
With reserves of 12.6 billion barrels, Majnoon is one of Iraq's major fields.