Study on the influence of blasting fracture on in-situ leaching laws of low permeability sandstones uranium deposit

Improving permeability of reservoir is the key method to solve the problem of in-situ leaching uranium from low permeability sandstones, and increasing the seepage channels by blast fracturing is an important means to enhance the permeability of the reservoir. In order to investigate the influence of blasting fracture on the yield laws of in-situ leaching uranium, establishes a numerical model of fractured sandstone uranium mine, and analyzes the influence of factors such as well spacing, driving differential pressure, fracture opening, and location of fracturing zone on ground leaching by observing the change of the effective leaching range and flow rate, and investigates the reasons for the dominant flow of the fracture. The study shows that in the case of one factor, with the increase of well spacing, the effective leaching range increases first and then decreases; with the increase of driving differential pressure, the effective leaching range gradually increases; with the increase of fracture opening, the effective leaching range gradually increases, and when the fracture opening increases to a certain value, the phenomenon of fracture dominant flow occurs, and the effective leaching range starts to decrease. Under the interaction of two factors, when the driving differential pressure increases, the increase of the fracture opening makes the effective leaching range and flow rate gradually increase, but the fracture is too large, and the dominant flow phenomenon is not conducive to the increase of the effective leaching range and flow rate; when the well spacing increases, the effect of the increase of the fracture opening on the increase of effective leaching range and flow rate decreases gradually; the increase of the driving differential pressure makes the peak effective leaching range corresponds to the well spacing is larger and the flow rate is smaller, so the well spacing is determined in the effective leaching range growth interval, when the effective leaching range and flow rate can achieve better effect. When the blast fracturing zone is located in the pumping wells, there is a large fracture at the wellhead, and the effective dissolved leaching range enhancement effect is obvious; when the blast fracturing zone is located between the pumping wells, the existence of a large fracture is prone to produce the phenomenon of fracture dominant flow, which is not conducive to the in-situ leaching. This paper clarifies the influence laws of various factors on the yield of in-situ leaching uranium, and clarifies the reasons for the generation of fracture dominant flow, contributes to the establishment of a complete production plan for in-situ leaching of sandstone uranium deposits.