FILE PHOTO: The logo of Venezuelan oil company PDVSA is seen on a tank at Isla refinery in Willemstad on the island of Curacao April 22, 2018. REUTERS/Andres Martinez Casares/File Photo

(Reuters) - Venezuela’s crude sales to the United States fell in August for the second month in a row as exports of two of the South American country’s main grades dropped following port interruptions by a tanker collision, according to Thomson Reuters Trade Flows data.

Venezuela’s state-run oil company Petróleos de Venezuela, S.A., known as PDVSA [PDVSA.UL], and its joint ventures last month exported an average of 468,300 barrels per day (bpd) of crude in 30 cargoes to their customers in the United States, the data show. The total was the third smallest monthly figure this year.

PDVSA’s oil shipments have been affected in recent weeks by export limitations at the country’s main oil port, Jose, after a minor tanker collision forced the state-run firm to halt operations at one of its three berths.

The Jose dock problem came as the country was attempting to reverse a series of blows to oil exports, including declining output, a severe lack of investment in its energy infrastructure and asset seizure attempts by creditors.

PDVSA last week started a contingency plan for diverting tankers waiting at Jose to load to the nearby terminal of Puerto la Cruz. It has not said for how long Jose’s loadings would be affected.

The state-run company last month exported to the United States a 500,000-barrel cargo of Merey crude and three 500,000-barrel cargoes of Zuata crude, two of the OPEC-nation’s main grades for exports. Both come from the Orinoco Belt, Venezuela’s largest oil producing region.

Crude upgraders at the Orinoco, essential for turning Venezuela’s extra heavy oil into exportable grades, have been working intermittently in recent months due to planned maintenance and outages, limiting volumes available for export.

U.S. refining firm Valero Energy was the largest receiver of Venezuelan crude last month with 153,000 bpd, followed by PDVSA’s unit Citgo Petroleum and Chevron Corp, according to the data.

Shipments to spot customers in the United States continued falling to some 40,000 bpd in August, the second smallest monthly figure so far this year.