A low permeability reservoirs usually have threshold pressure gradient with extremely low permeability. The seepage mechanism of multi-stage fractured horizontal wells are complex and the productivity are affected by many factors. Based on the dual-porosity medium seepage differential equation

applying point source theory and superposition principle

a semi-analytical productivity model for the multi-stage fractured horizontal wells is established

considering the threshold pressure gradient and hydraulic fracture conductivity. Then the calculation of production and the numerical inversion are conducted

following by the analyses of the influence factors combining specific examples. The study results show that the threshold pressure gradient has great effect on productivity. The larger the threshold pressure gradient is

the lower the production will be. The angle between the hydraulic fracture and wellbore has a little influence on production

but not obvious

and the highest production appears when the angle is 90°. The conductivity of the hydraulic fracture has obvious effect on the initial production

but a little influence on that in the later period. The hydraulic fracture at both ends of the horizontal wells affect more than that in the middle

so the fractured horizontal well’s stages and the length of the fracture should be increased. The storage ratio and cross flow coefficient mainly affect the medium-term productivity. The larger the storage ratio is

the faster the production will decrease. And the larger the cross flow coefficient is

the higher the production will be. The results of this study not only contributes to the deep understanding of the multistage fractured horizontal well’s seepage laws in the low permeability reservoirs

but also provides some important guidance and advice for the optimization design of the multi-stage fractured horizontal wells.