China's largest oil companies still lag far behind their foreign counterparts in terms of degree of internationalization, despite active forays into the global market through mergers and acquisitions last year, according to a research report released Thursday.

The report said the gap between China's three State-owned oil giants, namely China National Petroleum Corporation (CNPC), Sinopec Group and China National Offshore Oil Corp (CNOOC), and their foreign competitors remains huge in terms of percentage of overseas business and "transnationality Index (TNI)", a means of ranking multinational corporations by the ratios of foreign assets, foreign sales and foreign employment to their total amount, local newspaper Beijing Times reported Friday.

The TNI of the three oil giants average only 30 percent, about 50 percent lower than the international oil giants such as BP and Exxon Mobil.

The report is drafted by a think tank of CNPC.

The report also found China is becoming increasingly dependent on oil imports. In 2011, imported oil occupied more than 55 percent of the total consumption. The figure is expected to top 57 percent in 2012 as more than half of the imported oil is from the volatile Middle East.