In 2023, for example, a shell company connected to Mr. Malpica became the second largest exporter of Venezuela’s crude, just behind Chevron, a multinational firm that has produced oil in Venezuela for a century, the documents show.

Copies of some of the contracts show that the shell company, China-registered Hangzhou Energy, received oil from PDVSA on highly favorable and unusual terms despite not having any history of business activity. A contract for 2022 shows that Hangzhou was allowed to sell about a tenth of the country’s export volumes that year in return for providing the government with an unspecified amount of “humanitarian aid.”

It is unclear how much aid Hangzhou eventually delivered or what it included. Ostensibly set up in response to American sanctions, oil-for-food deals similar to the one obtained by Hangzhou became a major source of corruption during Mr. Maduro’s final years, siphoning billions of dollars from the state at a time of humanitarian crisis, according to the U.S. government and investigations by a Venezuelan news outlet, Armando.Info.

An email to Hangzhou’s operations manager, Zhang Junling, went unanswered.

Though Hangzhou’s legal representatives were ostensibly in China, in practice it was Mr. Malpica and a partner, Ramos Carretero, who represented Hangzhou in meetings with PDVSA, according to several PDVSA officials and people in Venezuelan oil industry, implying the two men were the company’s ultimate beneficiaries.

Hangzhou also had other unusual and lucrative payment arrangements.

Most oil buyers had to pay PDVSA in dollars. Hangzhou, however, paid Bandes, the development bank, in bolívars, the local currency, according to PDVSA documents, internal messages seen by The New York Times and interviews with Venezuelan oil officials.