From Holden:

OPEC is swapping dollars for euros.

Member nations of the Organization of the Petroleum Exporting Countries have cut the proportion of their deposits denominated in dollars by more than 13 percentage points in the past three years, mainly to the advantage of the euro, the Bank for International Settlements said Sunday.

[snip]

“Since the third quarter of 2001, oil revenue seems to have been channeled increasingly into euro and other currency deposits,” the bank said. “This shift out of U.S. dollars probably reflected to some extent the relative change in interest rates in the United States and the euro area since 1998.”