SANDEFJORD, Norway (Reuters) - The Norwegian government has awarded 28 oil and gas companies a total of 69 offshore blocks to explore for petroleum in mature areas of its continental shelf, the Norwegian Petroleum Directorate said on Tuesday.Shell , ConocoPhillips , Total and Equinor won blocks, as did DNO , Aker BP , Lundin Petroleum and Eni's Vaar Energi.Private-equity backed firms, such as Chrysoar, which acquired ConocoPhillips assets in the British North Sea last year, and Neptune..