Venezuela's oil shipments to India, its third largest export market, fell 21 percent to 280,000 barrels per day in the first half of this year, according to internal documents from state-run PDVSA seen by Reuters.

Venezuela's 30-year production low and shipping woes from years of mismanagement, underinvestment and payment delays are affecting all of its customers. But the impact on India is growing as its refiners are preparing for a "drastic reduction to zero" of oil imports from US-sanctioned Iran.