爆破裂隙对低渗砂岩铀矿地浸规律影响研究

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

    • 摘要: 提高储层渗透性是解决低渗砂岩地浸采铀的关键方法,通过爆破致裂来增加渗流通道是提升储层渗透性的重要手段。为探究爆破裂隙对地浸采铀产量规律的影响,建立了含裂隙砂岩型铀矿数值模型,通过观察有效溶浸范围与流量变化,分析井间距、驱替压差、裂隙开度、爆破致裂区位置等因素对地浸开采的影响规律,并研究了裂隙优势流产生的原因。研究结果表明:单因素情况下,随着井间距的增大,有效溶浸范围先增大后减小;随着驱替压差增大,有效溶浸范围逐渐增大;随着裂隙开度增大,有效溶浸范围逐渐增大,当裂隙开度增大到某一值时,产生裂隙优势流现象,有效溶浸范围开始减小。双因素交互作用下,当驱替压差增大时,裂隙开度增大使有效溶浸范围和流量逐渐增大,但裂隙过大,产生的优势流现象不利于有效溶浸范围和流量增大;当井间距增大时,裂隙开度增大对有效溶浸范围和流量增大的影响逐渐减小;驱替压差增大使有效溶浸范围峰值对应的井间距较大,而流量较小,因此,将井间距确定在有效溶浸范围增长区间,此时有效溶浸范围和流量能达到较好的效果。爆破致裂区位于抽注井时,井口出现大裂隙,有效溶浸范围提升效果明显;爆破致裂区位于抽注井之间时,大裂隙存在容易产生裂隙优势流现象,不利于地浸开采。本研究明确了各因素对地浸采铀产量的影响规律,明确了裂隙优势流产生的原因,有助于建立完整的砂岩铀矿地浸开采生产方案。

       

      Abstract: 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.

       

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