It is very difficult to say how much fossil fuel we have in this country which makes it hard to answer this question. For example, some people are of the view that North Sea oil reserves are depleting at a rapid rate and alternatives need to be explored.1
With regard to natural gas from shale, Dr James Verdon, geophysicist at the Bristol University told us that:
“The British Geological Survey has said that there is approximately 1,300tcf (trillion cubic feet) of gas in the Bowland Shale and, if 10 percent of this was found to be technically and economically extracted, this would correspond to about 40 years of the UK’s current gas consumption. However, shale gas won’t be used to meet 100% of the UK’s gas needs all at once: there will still also be gas coming from the North Sea, and imports from Norway and Holland. It is more likely that shale gas will at most meet 50% of the UK’s gas needs. This means that the 40 years of total gas use will actually be spread out over 80 – 100 years. This means that shale gas could be contributing to our economy for a long time to come.”
Most experts believe that the UK should have a mix of energy sources but should do more to reduce carbon emissions2. In 2013, renewables accounted for just over 5%% of the UK’s overall energy – including heating, transport and electricity – so natural gas will still be needed for some time as the share of renewables grows3.
Another way to look at your question is to consider whether we can import enough fossil fuel from elsewhere to keep the country going. The answer to this is, yes, for the foreseeable future. For gas, which 80% of UK homes rely on for their heating, this would mean investing more in our physical gas pipleline network with Europe and more in gas storage, whilst forgoing the benefits of producing our own.
According to Professor Richard Selley of Imperial College London: “The gap between UK-produced gas and imported gas has gradually widened since 2000. Centrica has recently signed a 2-year contract to import shale gas from the USA. Our increasing reliance on imports adversely affects the UK economy as declining UK gas production leads to declining tax revenue and has a negative effect on the trade balance.”
3 DECC, DUKES 2014, Chapter 6 https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/337684/chapter_6.pdf (“Progress has been made against the UK’s 15 per cent target introduced in the 2009 EU Renewable Directive. Using the methodology set out in the Directive, provisional calculations show that 5.2 per cent of energy consumption in 2013 came from renewable sources; this is up from 4.2 per cent in 2012.”)