Method and system for determining reasonable water drive lower limit of ultra-low permeability reservoir horizontal well development

The invention discloses a method and a system for determining a reasonable water drive lower limit of ultra-low permeability reservoir horizontal well development, and belongs to the field of oilfield development. By acquiring the radius of the throat, direct factors capable of restricting the flow capacity of the fluid can be realized, and the seepage capacity of the reservoir can be well reflected; the higher the ratio of the number of fractures in the non-safe range is, the higher the fractured water breakthrough risk is, and the more unfavorable water injection development is achieved; the obtained proportion of the water breakthrough producing well can determine the water injection development adaptability; according to the obtained yield, water injection development can be adopted when the yield is greater than 1; according to the average throat radius membership function, the fracture number proportion membership function within the unsafe range, the water breakthrough oil production well proportion me