LAGOS — Industry experts say a delay in moving to market-based gas prices will hold back investment in gas fields. The Nigerian Midstream and Downstream Petroleum Regulatory Authority has said a willing-buyer, willing-seller system is one to two years away. Chikezie Nwosu, chief executive of HSI Energies, told ThisDay that regulated prices discourage the development of gas fields, while publisher Toyin Akinosho said the electricity lobby is slowing the change.