Gas companies are now looking at using gas formed by hydrolysis of water to form hydrogen which is then converted into methane as a way of storage of excess renewable electricity when wind or solar produce more than is needed. See these ambitious plans for a North Sea Wind Hub with gas storage. http://www.4coffshore.com/windfarms/gas-company-joins-north-sea-wind-power-hub-consortium-nid6392.html They are talking about using existing North Sea gas pipelines to deliver gas which casts doubt on the wisdom of decommissioning them.
INEOS and co need to join them or join Ecotricity in turning grass to gas using anaerobic digestion, (https://www.ecotricity.co.uk/our-green-energy/our-green-gas/how-green-gas-works) We don't need fracking to provide the necessary gas, which may well be less than current needs as gas is being used much less for electricity production as renewables become cheaper and deliver more. There was more wind power than any other form of energy generation in the UK yesterday evening and night and in the summer solar often takes top spot now (see 'gridwatch' website)
We also are likely to need less gas for heating than we currently do as more buildings switch to heat pumps and become better insulated, so the estimate of how much gas is needed by 2030 may well be way out.