To start off, our country Malaysia is one of the exporters of both Petroleum and Natural Gas but we do them on a very small scale. In other words, our country is not as par as the OPEC countries, like Saudi Arabia.
Once we export those Petroleum and Natural Gas to other countries, we will get profit from the export. Some portion of the profits will be channeled to the government as the majority of Oil and Gas companies in Malaysia are Government Linked Companies, meaning some shares of profit would go to the government. So, some portion of the profits would be used to develop infrastructure of our country.
Besides that, those Petroleum and Natural Gas are two important sources/raw materials for some companies to produce goods and services. The profits that the companies earned will be taxed and the tax will be channeled to the government as a revenue. Some portion of the tax will be used for the development of our country.
Hope that helps. Cheers.