Numerical Simulation of Fracturing Naturally Fractured and Low-Permeability Reservoirs With Macro-Fracture

摘要

Fracturing is an important stimulation technique for naturally-fractured and low-permeability reservoirs. Based on the characteristics of fluid percolating in porous medium containing artificial fracture, natural fracture and matrix, we establish tri-medium percolation model of fracturing naturallyfractured reservoirs. In this paper, the macro-fracture and micro-fracture in the same grid are named as composite natural fracture. Taken mass exchange between macro-fracture and matrix into account, the multi-medium percolation model with macro-fracture is set up. The simulator of post-frac performance of fractured reservoirs is developed. Using the data of Tahe Oil Field in the northwestern China, we studied the effects of natural fracture and artificial fracture on post-frac performance and concluded that both of them have important meanings for fracturing optimum design of naturally-fractured reservoirs. The simulation results show that both the damage of natural fracture and the decrease of fracture conductivity with time greatly affected the post-frac productivity. Considering the damage of natural fracture, post-frac productivity may decrease correspondingly with the increase of the treatment scale. A reasonable treatment scale, therefore, should be selected. The productivity of fracturing well with macro-fracture is higher than that of fracturing well without macro-fracture and the time that water breaks through the well with macro-fracture may be earlier. Also the example of productivity history matching was given.