PetroChina said Tuesday it had signed a preliminary agreement with Anglo-Dutch oil giant Royal Dutch Shell and Qatar Petroleum International to study building a new refinery in China.

PetroChina would have a 51 percent shareholding in the new facility, while Qatar Petroleum International and Shell would each have 24.5 percent, the companies said in a statement.

They gave no details of the facility's cost, size or location.

PetroChina's chief executive Jiang Jiemen said the project would promote and strengthen cooperation with international oil companies.

The letter of intent was signed in Qatar's capital Doha and witnessed by Chinese Vice President Xi Jinping, who is on a visit to the Middle East where he is discussing the challenges posed by soaring oil prices.

Joining Xi were Qatar's Crown Prince Sheikh Tamim bin Hamad al-Thani and executives from the three oil companies.

"This project builds on a strong foundation of existing activities in Qatar and China, both of which are strategic to Shell," Royal Dutch Shell Executive Director Linda Cook was quoted as saying in the statement.

Both Shell and the Qatari government have been actively looking for investments in China, the world's second largest oil consumer.

PetroChina signed a deal in Beijing last month with Qatargas and Shell under which the Chinese firm would buy three million tonnes of Qatari LNG per year for 25 years, according to a statement issued by the companies.