The agency expects investment to fall by more than 21 percent from this year's record of 231.7 billion kroner ($38bn).
"The decrease is mainly due to significantly lower estimates of field development and fields on stream," the agency wrote in a report posted on Thursday. "The estimates indicate an increased investment in exploration."
Investment on field development and producing fields is expected to come to 131.8 billion kroner, 33.4 billion kroner lower than the estimate for 2014.
Marius Gonsholt Hov, an analyst at Svenska Handelsbanken AB (SHBA), said in a note that the “dramatic decline” in oil investments was likely to prevent the country's central bank from raising interest rates until well into the second half of next year.