A drop in gas field production has forced the shutdown of the Northern Gas Pipeline. 

Production from an offshore field that supplies gas for the Top End's electricity generation has decreased by nearly 50 per cent this year. 

The NT Government-owned Power and Water Corporation (PWC) has a deal with Italian company ENI to buy gas from the Blacktip field until 2031, and use it to generate electricity for the Darwin to Katherine grid.

Over the past 12 months, gas output from the field has been steadily dropping.

Blacktip's production drop means there is now not enough gas to run the Tennant Creek to Mount Isa pipeline, where PWC normally sends its excess supply.

Wood Mackenzie energy research analyst Anne Forbes says Blacktip's problems are concerning.

“There's been quite a significant [production] decline, much more severe than we would generally assume would happen for this type of gas field,” she said.

“It's been quite unexpected.”

The Blacktip field includes 12 separate stacked reservoirs on four different geological formations, making it difficult to extract gas from.

“[A gas reservoir] will always not perform as you expect — it might be better or it might be worse,” Ms Forbes said. 

“In this case it's not been as good as [ENI] had hoped.”

PWC says it has emergency backup supply agreements with LNG exporters in Darwin Harbour - Santos and Inpex, but will not confirm if Blacktip is supplying enough gas to meet demand from its power plants,

Information from the Australian Energy Market Operator and the Australian Energy Market Commission allegedly suggests there is a current gas shortfall of around 19 terajoules per day.

If that is the case, PWC would be receiving enough gas to keep the NT's lights on, but is likely having to rely on emergency supplies.