Venezuela has begun shutting wells that pump extra-heavy crude in the Orinoco Belt, as the U.S. blockade is squeezing shipments and filling up storage space, sources with knowledge of the plans of state oil firm PDVSA told Bloomberg. PDVSA, the key handler of Venezuela’s crude exports, mostly to China, began disabling producing wells in the Orinoco Belt two days ago, following a decision taken on December 23, according to Bloomberg’s anonymous sources. The state oil firm will look to shut in about 15% of Venezuela’s total…