June 6 (Reuters) - Venezuela's 187,000-barrel-per-day Puerto la Cruz refinery is running at 16 percent of capacity, mainly due to a lack of light oil as state-run PDVSA ships a portion of its Mesa 30 crude to Cuba and Curacao, according to internal trade reports and workers.
Oil company PDVSA in March resumed exports of Mesa 30 to Cuba after an eight-month pause. It has shipped between 850,000 barrels and 1.4 million barrels per month to the Caribbean island since then, documents show.
Mesa 30 - one of Venezuela's lightest crudes - is used by PDVSA and its partners to dilute the extra heavy oil produced in the vast Orinoco Belt and to feed several domestic refineries. But with its oil output falling, the company is struggling to satisfy its domestic network and its foreign clients, according to internal sources and reports.
"Diverting crude is one of the causes of the refinery's status, but there is also lack of maintenance," said Jose Bodas, a union leader at Puerto la Cruz who last month warned about the facility's low processing.
Workers in May failed to restart Puerto la Cruz's catalytic cracker due to lack of spare parts, Bodas added.
Only one of Puerto la Cruz's three crude distillation units is working after the refinery partially resumed operations last week, a worker from the facility told Reuters.
The refinery is producing about 29,500 bpd of gasoline, diesel and residual fuels, another worker said.
Venezuela's refining network has been running at historic lows this quarter, causing intermittent gasoline shortages in the OPEC-member country and in Cuba. Only PDVSA's smallest refinery, the 146,000-bpd El Palito, has increased output since April.
The 335,000-bpd Isla refinery in Curacao, which PDVSA uses as an auxiliary facility, also has struggled to increase output since one of its four crude distillation units suffered serious damage during a fire two weeks ago.
"Isla is putting its thermal cracker unit in service to be used for crude distillation... so it can process 40 percent of the crude bound for the crude distillation unit number 3," the refinery said in a statement late on Monday.
The refinery also will process heavy crude at its distillation unit number two, it added.
Isla produces fuel oil for export, mainly for delivery to Chinese firms as payment for loans to Venezuela. The fire has contributed to PDVSA's low fuel oil shipments, which this year average 60,000 bpd versus 165,000 bpd in 2016, according to the data.
Two 500,000-barrel cargoes of British BP supplied U.S. light sweet crude arrived in Curacao's Bullenbay terminal in May to feed Isla's since damaged crude unit. PDVSA is considering diverting the oil to its Amuay refinery on Venezuela's western coast, one of the internal documents says. (Reporting by Marianna Parraga in Houston, Mircely Guanipa in Punto Fijo, Venezuela and Sailu Urribarri in Oranjestad; Editing by Dan Grebler)