July 10 (Bloomberg) -- Daily shipments of the four North Sea crude grades that determine the price of Dated Brent, the benchmark for almost two-thirds of the world’s oil, will sink 27 percent next month as fields are idled for maintenance.

Combined loadings of Brent, Forties, Oseberg and Ekofisk crude will decline to 1.03 million barrels a day, down from 1.406 million barrels a day in July, according to Bloomberg calculations from schedules released today and yesterday.

The total scheduled for loading in August will fall to 32 million barrels from 43.6 million barrels in July.

Exports of Forties crude, which comprises almost half of the total, will collapse the most, falling 53 percent as Nexen Inc. closes the Buzzard field that feeds into the Forties Pipeline System.

Loadings of two of the other three grades will also contract, with Brent itself shrinking 13 percent to 135,484 barrels a day and Oseberg tumbling 9.6 percent to 193.839 a day, the loading programs show. Only Ekofisk will rise, by 3.8 percent to 393,548 barrels a day.

Dated Brent is set by the cheapest of Brent, Forties, Oseberg and Ekofisk cargoes loading about three weeks in the future. It’s a benchmark for oil in Europe, Africa and Russia.

To contact the reporter on this story: Alexander Kwiatkowski in London at akwiatkowsk2@bloomberg.netGrant Smith in London at gsmith52@bloomberg.net

Last Updated: July 10, 2009 06:34 EDT