Plunging oil prices have rendered more than a trillion dollars of future spending on energy projects uneconomic, according to a study that suggests that the impact on industry operators is worsening. A report published Monday says $1.5tn of potential investment globally — including in North America’s shale-producing heartlands — is “out of the money” at current oil prices close to $50 a barrel and unlikely to go ahead. Industry operators expect capital spending on new projects to decline by between 20 and 30 per cent on average in the wake of the price slide, says Wood Mackenzie, the energy consultancy. It calculates that $220bn of investment has been cut so far, about $20bn more than it estimated two months ago and much of it the result of projects being deferred. Such a decline in spending means that the price crash since last summer — the result of weaker Chinese demand, record US production and Saudi Arabia’s decision not to cut output — could resemble the savage downturn of the mid-1980s.