Effect of the angle between hydraulic fracture and natural fracture on water flooding in tight reservoirs

In order to study the effect of the angle between hydraulic fracture and natural fracture on water displacement effect, a non-piston water flooding oil-water two-phase one-way seepage model was established considering the influence of both gravity and fracture on water displacement. And finite element method (FEM) was used to quantitatively analyze water displacement effect when the angle between hydraulic fracture and natural fracture was 0°~90° by production and the distribution of oil content. Results show that: the higher the angle between hydraulic fracture and natural fracture, the higher the oil well production. When the angle between hydraulic fracture and natural fracture was 90°, the cumulative production of oil well was the highest, and the production of oil well decline rate was the slowest; the greater the angle between hydraulic fracture and natural fracture was, the wider the spread range of injected water was in matrix system, and the effect of water flooding was remarkable. When the angle between hydraulic fracture and natural fracture is 90°, the water flooding effect in fracture and matrix systems was better than other fracture distributions, the spread range of injected water was the widest, and the remaining oil was the least, but the overall efficiency of water displacement was low. The research results are helpful to understand the effect of fracture distribution on water flooding development and prevent water breakthrough.