Shell Nigeria Exploration and Production Company (SNEPCo) has halted production at Nigeria's Bonga oil field.
The exercise, which commenced on March 4, was put in place for maintenance that will last at least a month.
SNEPCo said in a statement that Bonga, Nigeria's first deepwater development, is expected to resume production at some point in April, without giving further details.
Reuters news agency reports that market sources had expected work on the field because there were no exports planned in March, compared with typical exports of roughly 200,000 barrels per day (bpd).
Bonga produced an average of 192,500 bpd of oil in 2015, according to the latest annual data from Nigerian state oil company NNPC.
The nation's first deepwater development has capacity to produce 225,000 barrels per day (bpd) of oil and 150 million standard cubicfeet (scf) of gas.
The new development has forced Nigeria's oil production down to 1.875million bpd, from the 2.1 million bpd recorded in recent time.