L and M Coal Seam Gas Ltd and L and M Central Otago Lignite Ltd hold exploration permits for the land excluded from the park boundary.
Conservation Minister Tim Groser announced changes to the boundary of the park, to exclude a 195ha area over the Hawkdun lignite deposit, which is deemed a significant resource of recoverable energy.
Mr Groser said the change was a small one in terms of the park's total area, although it was of significant importance to the decisions of future energy generators.
"Hawkdun could yield liquid fuels equivalent to New Zealand's transport requirements for 15 to 20 years," he said.
Mining company L and M Group opposed Doc's proposal for the park when it was originally notified.
The company's submission against Oteake stated the Hawkdun coalfield contained an estimated one billion tonnes of lignite rank coal and had the potential to contain up to 50 petajoules of coal seam gas.
Yesterday, L and M Group managing director Greg Hogan told the Otago Daily Times the company was in its second year of a feasibility study for its Hawkdun exploration site, and this week's announcement would mean the study could continue as planned for another two and a-half years.
"L and M welcomes the announcement. It has given us sufficient confidence to go ahead with additional investment to complete the feasibility study."
L and M had suggested the park's boundary be altered to eliminate an overlap with the coal resource.
"If we didn't get the announcement, we would have had to consider our position," he said.
The Hawkdun site was one of five areas in New Zealand the company was exploring for mining. Its main permit for the Hawkdun coalfield would expire on February 15, 2012, by which time the study should be completed, Mr Hogan said.
Although the area over the deposit would remain protected public conservation land, exploration should be able to continue unimpeded, Mr Hogan said.
