A global oil conference concluded Thursday in South Africa's Johannesburg with calls for more investment in African oil. While delegates from around the world argue over high oil price, clean energy including a green gas to liquid technology steal some of the show as world oil supply tightens.

The 18th World Petroleum Congress was convened against a backdrop where Africa plays increasingly important role in the global oil market, in which crude oil prices have soared sky-high during the past two years.

People's Daily