Capital spending on U.S. and Canadian oil and gas pipelines and other “midstream” energy infrastructure will average, to 2035, an estimated $26 billion a year, according to a new study from the Interstate Natural Gas Association of America (INGAA). That total is down from a 2014 INGAA forecast.

The new analysis, released on April 12, provides a range of spending estimates, from a “low case” of $471 billion, or an average of $22.4 billion a year, to a “high case” of $621 billion, or an annual $29.6 billion. The midpoint total is $546 billion, or $26 billion per year.

By comparison, the last INGAA report, released in 2014, estimated spending at $29.1 billion annually. The forecast didn’t include a range of predictions. Both reports were done for the INGAA Foundation by ICF International, Fairfax, Va.

The new study’s low case, based on slower economic growth, estimates natural-gas demand climbing, by 2035, to 110 billion cu ft (Bcf) per day; the high case projects usage of more than 130 Bcf a day.

The 2016 report says natural-gas infrastructure spending accounts for $310 billion, or 57% of the midpoint total; oil and natural-gas liquids expenditures would be $212 billion, and integrity management and emissions control would be $24 billion.

The report’s midpoint forecast includes $166 billion to be spent on oil and gas pipelines. It foresees 296,000 miles of gathering and transport pipelines to be installed through 2035.

Gathering systems, including pipe, compressors, pumps, and processing and fractionation equipment, will be $116 billion over the 2015-35 period.

Gas-storage spending, including facilities for liquefied natural gas and natural gas liquids, is estimated at $85 billion; all other infrastructure would comprise $155 billion.

The 2014 report estimated total oil-and-gas capital expenditures at $641 billion over the 2014-35 period, including $313 billion for natural gas, $56 billion for natural gas liquids and $272 billion for crude oil.

INGAA Foundation President Don Santa said in a statement, “We saw a need to reexamine infrastructure needs in light of significantly lower commodity prices.”

He added, “While [exploration and production] activity may dip temporarily because of lower prices, we still will need significant capital investment, particularly in natural-gas midstream infrastructure.”