The tiny emirate, which is determined to become the world's top exporter of liquefied natural gas (LNG), said it plans to create a financial centre to rival similar entities in the neighbouring United Arab Emirates and Bahrain.
Economy and Trade Minister Muhammad bin Ahmad bin Jasim al-Thani said on Thursday that $50 billion would be spent on infrastructure projects and the rest on oil and gas ventures.
Energy and Industry Minister Abd Allah bin Hamad al-Attiya had announced on Wednesday plans to invest $75 billion on a string of massive projects by 2012.
"Most of the projects are linked to the oil and gas sectors, but they form part of the state strategy to diversify sources of revenue," said al-Attiya.
The minister said Qatargas would make the country the world's largest LNG exporter, with production rising to more than 88 million tonnes in 2012 from a projected 20 million this year.
Qatar's giant North Field has proven gas reserves of more than 25 trillion cubic metres - the third largest in the world after Russia and Iran.
It amounts to more than 15% of the world's total proven gas reserves, and is enough to last the Gulf state about 250 years.