Novel method for predicting relative permeability of low-permeability reservoir

The invention belongs to the technical field of oil-gas field development, and relates to a novel method for predicting the relative permeability of a low-permeability reservoir. A percolation threshold theory is utilized, a low-permeability oil reservoir constant-speed mercury injection test result is combined, a three-dimensional pore throat network distribution model considering gravity influence in the vertical direction is established on the basis of a microscopic motion equation considering solid-liquid molecular force action, a large linear equation set is combined, pore node pressure is solved, and the oil-water relative permeability is calculated. Compared with a traditional core displacement experiment, the method has the advantages that the influence of a microscale effect and gravity is considered, the movement rule of fluid in a reservoir can be reflected more truly, the oil-water relative permeability can be calculated quickly and accurately according to the pore throat characteristics of the lo