Some of the most significant ramifications of the death of Hugo Chavez for the U.S., both short-term and long-term, may have little to do with the late ruler's politics and more to do with his country's oil.

Venezuela is one of the world's biggest oil exporters and one of the top five suppliers to the U.S. As a result, any sign of instability following Mr. Chavez's death could roil oil markets, boost crude prices and dent the global economy.

Even a Chavista successor to Mr. Chavez--such as current Vice President Nicolas Maduro-- could have a tough time maintaining the heterogeneous coalition of socialists, businessmen, and the military that has coalesced around Mr. Chavez.

"Instability in Venezuela is the real risk, because that could have a dramatic impact on global oil supplies," said Mark Jones, a Venezuela expert at Rice University.

Venezuela produces about 2.5 million barrels of oil a day and supplies about 1 million barrels a day to the U.S. Oil wealth, especially in the middle of the last decade, underwrote Mr. Chavez's "Bolivarian revolution" and allowed lavish spending on social programs.

But chronic underinvestment in the state oil company, Petroleos de Venezuela, and hostility to foreign firms has steadily eroded the country's oil-production capacity, leaving the future murky.

Mr. Chavez's death also could have knock-on effects throughout the region.

Venezuela provides about 100,000 barrels of oil a day to Cuba, essentially free--a $3 billion to $4 billion annual subsidy that could disappear if Mr. Chavez is replaced by an opposition candidate.

That would be devastating to Cuba, comparable to the economic hardship the island suffered after the implosion of its main sponsor, the Soviet Union, in the early 1990s.

Venezuela also provides subsidized oil to Nicaragua and sells oil to other Caribbean nations on preferential terms--meaning any political upheaval in Caracas could harm economic growth throughout the region.

Whoever succeeds Mr. Chavez likely will seek to maintain oil trade with the U.S. and, if possible, to boost investment in the oil sector.

"We've had this symbiotic relationship--Chavez has been a diplomatic thorn in our side, but his revolution and regime are built largely on oil sales to the U.S., and that relationship is likely continue," Mr. Jones said.

Oil analysts see opposition candidate Henrique Capriles as a more business-friendly candidate, one who could try to open the Venezuelan energy sector to much-needed foreign investment, similar to policies favored by the new Mexican president, Enrique Pena Nieto.

But while major U.S. oil companies would like access to Venezuela's ample reserves of heavy crude, the country's past expropriations of foreign energy firms' assets could also damp enthusiasm for a quick return to the country.

For many industry participants, the problem comes down to a single question: Would foreign oil companies be asked back to Venezuela to revive its stagnant oil industry?

"It's the million dollar question, whether they'll open up or not," Bobby Tudor, president of energy investment firm Tudor Pickering Holt Co., said on the sidelines of the IHS CERAWeek conference in Houston.