PetroChina valued just below Apple

There are lots of ways to climb the ranks of the world's largest companies.

Apple Inc surged to the top by making must-have gadgets with big profit margins. Berkshire Hathaway Inc harnessed the stock-picking genius of veteran investor Warren Buffett in the United States. And Google Inc created a lightning-fast search engine.

Now PetroChina Co is doing it the Chinese way - with help from government intervention.