Roc Oil and its partners have signed an agreement with China National Offshore Oil Corporation (CNOOC Group) on explorations in two offshore oil fields in southern China, the Australian firm announced in a statement on its website Wednesday.

The two offshore oil fields cover an area of 82.1 square kilometers, and plans are in the works to start production in the second half of 2012 at a combined rate of up to 20,000 barrels per day.

CNOOC Group is the third-largest oil company in China following CNPC and Sinopec. The State-owned company focuses on oil and natural gas exploration and refining in China's sea areas. CNOOC Group is the parent of the Hong Kong- and New York-listed Cnooc Ltd.

Phone calls to CNOOC Group went unanswered Wednesday, as usual.

Cnooc will take a 51 percent stake in the block, valued at $300 million.

"In addition to the commercial terms, the agreement also outlines arrangements regarding facility integration and the sharing of services and personnel," Roc Oil said in the statement.

The final investment decision is expected in the second quarter after CNOOC Group approves the overall development plan.

The deal lowers Roc's share in the block by 1.5 percentage points to 19.6 percent. It also reduces the interests of Roc's partner, Sydney-based Petsec Energy, to 12.25 percent, according to Roc Oil.

The Australian oil company began farming the area in 2002 with a 25 percent interest. Since then, Roc drilled six exploration wells in the block.

ROC released its first half earning Wednesday. Its net profit for the first six months of the year was $6.7 million, a turnaround from a loss of $14.2 million in the same period of 2009.

First half revenue was down two percent at $100.2 million. Net cashflow for the first half totaled $40.3 million, boosting Roc's net cash to $52.7 million.

Roc remained on target to meet its 2010 production guidance of 8,000 to 9,000 barrels per day. Development and exploration expenditure would increase in the second half, said Bruce Clement, the company's chief executive, in the statement.