Iran faces major obstacles in redirecting oil exports through the Caspian Sea following the US naval blockade. Existing pipelines cannot transport large volumes of crude northward, while tanker capacity is limited. Russia, Azerbaijan and Kazakhstan offer few practical alternatives. Despite speculation about bypassing sanctions through Russian routes, substantial infrastructure gaps make large-scale exports to China highly unlikely.
Source
https://maritime-executive.com/editorials/iran-has-few-options-for-northbound-oil-shipments