With more than half of the potential reserves offshore Norway untapped, the government said the industry needs to take the long view in the depressed market.

The Norwegian Petroleum Directorate, the nation's energy regulator, published its annual review of activity in its territorial waters. NPD Director General Bente Nyland said lower crude oil prices means nearly half of the continental shelf's potential may be left idled as energy companies trim operational expenses.

"We see a tendency for the companies to prioritize short-term earnings rather than long-term value creation," she said in a statement.

Data gathered by Statistics Norway, the government's record-keeping agency, found total investments in oil, gas, manufacturing, mining and electricity for 2015 were around $28 billion, down 9.4 percent year-on-year. For oil and gas alone, the year-on-year decline was 11.8 percent.

NPD said industry investments are expected to remain suppressed through the latter half of the decade, with levels expected to hold at around $22.5 billion for the next few years before a moderate uptick by 2019.

Norway is one of the regional economy's largest suppliers of oil and natural gas. Lower crude oil prices means less revenue not only for the industry, but for exporting economies like Norway's. Economic growth for Norway has been consistently below 1 percent.

Nevertheless, NPD said offshore activity was robust when compared to 10 years ago. Even though most of the discoveries were considered minor, the agency said there were 17 discoveries made in territorial waters last year and 82 fields in operation at the end of 2015, a 60 percent increase from 2005.

"Activity will remain high in the years to come, in spite of the [industry] decline since 2014," Bente said. "Therefore, it is important that the companies make wise decisions and keep a long-term perspective."