Crude oil drips from a valve at an oil well operated by Venezuela's state oil company PDVSA, in the oil rich Orinoco belt, near Morichal at the state of Monagas April 16, 2015. REUTERS/Carlos Garcia Rawlins/File Photo

HOUSTON (Reuters) - Sales of Venezuelan crude to the United States fell 23 percent in October to 601,605 barrels per day (bpd) due to fewer shipments of diluted oil from the country’s main producing region, the Orinoco belt, according to Thomson Reuters trade flows data.

Venezuela’s oil production has declined sharply this year due to years of underinvestment, payment delays to suppliers and lack of enough diluents to make exportable crude blends, which has affected exports of state-run oil firm PDVSA.

The United States, one of PDVSA’s top destinations for exports, received 37 cargoes of Venezuelan crudes last month compared with 46 cargoes in September and 50 cargoes in October of 2015, according to the data.

The export decline is attributed to a large decrease in shipments of diluted crude oil (DCO), a mix of Venezuelan extra heavy oil and imported naphtha, which fell to 85,840 bpd last month, its lowest since the second quarter of 2015.

PDVSA’s refining unit Citgo Petroleum, U.S. Chevron Corp and Phillips 66 were the main receivers of Venezuelan oil in the United States in October.

Refining firm Valero Energy, which has been a large importer of Venezuelan oil in recent years, continued suffering a decline in crude shipments from PDVSA.

For its part, PDVSA imported several cargoes of diesel, gasoil, liquefied petroleum gas (LPG), gasoline blend stock and heavy naphtha for the Venezuelan domestic market last month, according to Thomson Reuters vessel tracking data.

As of Nov. 2, about a dozen tankers with imported crude and refined products were anchored around PDVSA’s ports in the Caribbean sea, waiting to be paid before authorizing discharge.