In the Umm Shaif and Nasr concession, PetroChina joins France's TOTAL and Italy's Eni which were recently awarded a 20 percent and 10 percent stake respectively.

In the Lower Zakum concession, CNPC joins an Indian consortium led by ONGC Videsh, Japan's INPEX, TOTAL and Eni.

ADNOC retains a 60 percent majority share in both concessions.

"These agreements strengthen our growing relationship with ADNOC, and will help to meet China's expanding demand for energy and contribute to asset portfolio optimization and profitability enhancement of PetroChina," Wang Yilin, who is chairman of both PetroChina and its parent China National Petroleum Corporation (CNPC), said in a statement.

The 40-year agreements, signed by ADNOC and CNPC, are backdated to March 9, 2018, ADNOC said.

In February 2017, CNPC, China's largest oil and gas producer, was awarded an 8 percent interest in Abu Dhabi's onshore concession, operated by ADNOC Onshore. It also has a 40 percent stake in the Al Yasat concession with ADNOC.

"Energy cooperation is an increasingly important aspect of the UAE's relations with China, the No. 1 oil importer globally and a major growth market for our products and petrochemicals," ADNOC Group Chief Executive Sultan Ahmed al Jaber said in the statement.