Only a quarter of the shale gas in one of the UK's biggest reserves might be recoverable due to limited space to develop the necessary wells, academics have said.
The Bowland Shale - the rock thought to hold most of our shale gas reserves - is found throughout large parts of northern England, as well as parts of the Midlands, north Wales and the Isle of Man.
Immovable infrastructure such as buildings, roads and rivers put constraints on the area of the Bowland Shale that could be developed, say researchers from experts consortium ReFINE (Research Fracking in Europe).
They mapped possible sites on to the areas licensed for potential gas extraction.
They concluded that within a typical 10km by 10km square, only a quarter of the area could accommodate wells when existing properties, natural features and transport links were factored in.