China Petroleum & Chemical Corp (Sinopec), the world's third-largest oil refiner by capacity, said first-quarter profit more than doubled, thanks to weaker oil prices that made its refinery business profitable.

Net profit rose to 20.28 billion yuan in the first three months from 9.73 billion yuan a year ago, based on international accounting standards.

Turnover surged 23.2 per cent to 274.4 billion yuan from 222.7 billion yuan.

An operating profit of 4.17 billion yuan at its refining unit, compared with a 7.88 billion yuan loss a year earlier, more than offset a 32.15 per cent slump in operating profit from exploration and production to 11.65 billion yuan.

The turnaround in the refining business was due mainly to the drop in the price of crude oil, a raw material the company needs in order to manufacture fuel products such as diesel.

About 70 per cent of the company's oil needs are imported.

Crude oil prices in New York dropped 8.3 per cent to an average of US$58.225 a barrel in the first quarter from US$63.477 in the same period last year.

The company also said that earnings growth was driven by strong demand in the domestic market for refined oil products and higher selling prices.

The mainland government, which regulated the retail fuel market, adjusted prices over the past year.

As a result, Sinopec's operating profit at the sales and distribution unit surged 132 per cent to 7.74 billion yuan in the first quarter from 3.32 billion yuan a year earlier.

Operating profit for fuel and chemicals sales jumped 96.77 per cent to 6.19 billion yuan.

Crude output rose 2 per cent to 9.99 million tonnes from 9.79 million tonnes previously.

However, the average crude oil selling price dropped 17 per cent to 2,582.70 yuan per tonne from 3,112.81 yuan.

Investment bank UBS said in a research note last week that Sinopec's profit might have peaked in the first quarter as crude oil prices rebounded, which would reduce the margins from producing fuels at state-controlled prices.

Shares in Sinopec dropped 2.47 per cent in Hong Kong on Friday to close at HK$7.10.