India, Jan. 10 -- A new chapter in the fight over Venezuela's oil has emerged as a fleet of tankers skirted a U.S. blockade only to come back into Venezuelan waters, highlighting how complex and contested global energy politics have become. About a dozen vessels laden with crude sailed in early January with their tracking systems turned off-a tactic often referred to as "dark mode." At least four of those tankers-most carrying oil-have now returned to Venezuela, underscoring both the limits of U.S. enforcement and the desperation of Caracas to keep its vital exports flowing amid strict sanctions under President Donald Trump's blockade.

The four Venezuelan tankers that returned home after sailing in "dark mode" amid the U.S. blockade are:...