IGas said it conducted an analysis of some 20 wells in a 300-square-mile area where it's the exclusive license owner.
Chief Executive Officer Andrew Austin said in a statement a thorough analysis of the area "supports our view that these licenses have a very significant shale gas resource with the potential to transform the company and materially benefit the communities in which we operate."
The estimate of 170 trillion cubic feet was the high-end assessment from the Bowland Shale license area. The low end was around 15 trillion cubic feet of natural gas.
British gas explorer Cuadrilla Resources said in March it believes there are 200 trillion cubic feet of shale natural gas in the Bowland basin in Lancashire.
The controversial shale exploration technique known as hydraulic fracturing, or fracking, was suspended briefly in 2011 when Caudrilla reported small tremors. The British government last year lifted the fracking ban as it enacted a risk-control measure based on a "traffic light" system.
IGas said in a statement it would begin a drilling program during the fourth quarter of the year.