(MENAFN - AFP) Venezuela's vast nationalised oil sector needs to open up to foreign investors if it is to develop but there is little likelihood of a rapid change following the death of president Hugo Chavez, analysts say.Chavez used oil as a political and propaganda tool and his passing has focused attention on what will happen next to the largest proven crude oil reserves in the world.Oil prices slid on Wednesday, having earlier rebounded on uncertainty following Chavez's death. The market then accelerated losses after signs of weak demand in the United States, the world's leading oil consumer."President Chavez going out of the picture is a big game-changer," Diego Moya-Ocampos, analyst at IHS Global Insight, told AFP."He leaves a power vacuum (in Venezuela) which will be very, very hard to fill."Moya-Ocampos believed that if Chavez's chosen successor Nicolas Maduro won elections that could be held within a month, little would change in the short term."If Maduro is elected, we could expect some policy continuity, and the same sort of nationalist approach."Analysts at JBC Energy agreed: "We do not expect large changes to Venezuela's oil policies and see only a minor chance for greater openness towards foreign investors, especially as current arbitration cases against IOCs (International Oil Companies) are still ongoing."The US giant ConocoPhillips is one of the companies in dispute with Venezuela.Chavez's rise was closely linked to oil. He nationalised some assets owned by international oil companies and put the state company PDVSA in control of all oil and gas projects.Following his election in 1998, Chavez profited from the dizzying rise in crude prices which increased tenfold in a decade, investing billions of dollars of the profits into 'social inclusion' projects for the poor.Chavez also used the oil to keep his allies close. Venezuela supplied 100,000 barrels of crude a day at preferential rates in exchange for medical personnel. Chavez also sent Nicaragua 10 million barrels of oil a year and Uruguay received between six and eight billion barrels a year.But it is China that could suffer most from any breakdown in the special relationship it cultivated with Chavez's regime.China has agreed to lend Venezuela around 50 billion through the Chinese Development Bank in return for shipments of crude oil. "Beijing will be worried about the future of this strategic investment," said Jean-Francois Dufour, an analyst at the French company DCA Chine-Analyse.David Rees, of Capital Economics, said: "The uncertain political outlook could discourage future petro-loans from China."With oil revenues providing 90 percent of Venezuela's foreign earnings, Chavez's likely successor Maduro will probably have to increase oil output to maintain the social inclusion policy, Moya-Ocampos said.And that, he believes, could see international oil companies being allowed to play a bigger role."It will lead to a situation where... particularly in the oil-rich Orinoco Belt, we can expect some flexibility."Because at the moment, what we're seeing is that most of the companies are in wait-and-see" mode until it is clear who will lead the country.Production decreased 25 percent under Chavez's rule and the sorely-needed influx of foreign investment to increase output will not come overnight."It took Mr Chavez ten years to run the oil industry down and it might take just as long to get it back again," Rees said.Whatever happens, Venezuela will remain a major player in the oil market. According to BP economists, it has the largest proven reserves of crude in the world, with 296 billion barrels, compared with 265 billion barrels for Saudi Arabia.Despite Chavez's hostile relationship with US politicians, Venezuela exported 36 percent of its oil production to the United States in 2012.