State-owned Guangdong Rising Assets Management Co Ltd (GRAM) bought into Frieda River in 2015, in line with moves by Chinese companies to pursue offshore copper mines to feed demand in the world's biggest user of the metal.
The project has still to gain formal financing and no date has been set for construction, said Joe Walsh, corporate development officer at GRAM subsidiary PanAust.
The capital cost for Frieda River is more than double the US$1.7 billion estimate made in September 2014 by PanAust, before it was acquired by GRAM for around US$950 million.
The increase reflects a larger annual production capacity, as well as extra spending on waste management and rising construction costs, according to a document released by Highlands Pacific Ltd, which has a 20 percent stake in the project.
An additional US$2.3 billion would also be spent over the life of the mine, the document said.
Copper has been earmarked as one of the few growth markets for mining companies stung by a slowdown in metals directly related to steelmaking, such as iron ore and nickel.
China Molybdenum paid US$2.65 billion for Freeport McMoran's majority stake on the Tenke copper project in Democratic Republic of Congo this month and US$820 million for the Northparkes copper mine in Australia in 2013.
In 2014, Hong Kong-listed MMG Ltd bought the Las Bambas copper project in Peru off Glencore for US$5.85 billion.
Copper is languishing near its lowest price in seven years due to a supply glut. With fewer discoveries, however, miners exploiting new lodes hope by the time they are up and running, the market will have turned.