Establishment of the productivity prediction method of Class III gas hydrate developed by depressurization and horizontal well based on production performance and inflow relationship

•Method to establish prediction formulas for Class III gas hydrate developed by depressurization and horizontal well.•Production performance and energy consumption of gas hydrate development.•New index is introduced to revise Fetkovich’s formula and Vogel’s formula.•The revised formula can simplify the production prediction of gas hydrate.