低渗透含铀砂岩压力梯度-黏度-化学耦合渗流规律实验研究

摘要

To study the seepage law of low‐permeability sandstone uranium ore rock under the physical and chemical coupling action , and provide a reliable basis for the design of parameters for in‐situ leaching ,some samples of sandstone from a uranium mine in Xinjiang were used to carry out experimental research by a homemade permea‐bility test device . T he results indicate that there are three seepage stages in the low‐permeability rock ,namely ,the stage of starting pressure ,the stage of nonlinear seepage and the stage of linear seepage .With the change of fluid viscosity ,the percentage that fluid flow voids occupied in the w hole rock voids and the rock permeability on the w hole can be changed .In the early stage of physical and chemical coupling seepage ,after the media of ore and leaching agent reacting chemically ,the pore structure of medium ore is altered ,and some of the smaller radius of pore is larger and connected ,w hich makes the seepage of fluid larger in the unit area and per unit time ,thereby enabling the overall permeability of sandstone medium becomes larger .In the latter stage of physical and chemical coupling seepage ,due to the pressure and chemical coupling ,the pore struc‐ture further evolves .When the pressure gradient is more sensitive than chemical sensi‐tivity of reaction ,the permeability coefficient increases ,w hereas decreases .%研究低渗透性含铀砂岩物理化学耦合作用下的渗流规律，可为地浸工艺参数的设计提供可靠依据。本文选取我国新疆某铀矿山砂岩样品，用自制的渗透性测定实验装置，开展了含铀砂岩原样的物理化学渗流规律的实验研究。结果表明：该低渗透性矿岩存在3个渗流阶段，即启动压力阶段、非线性渗流阶段和线性渗流阶段；改变流体的黏度，可改变流体流通空隙所占的百分比，进而整体上改变矿岩渗透性能；在物理化学渗流前期，矿岩介质与溶浸剂发生化学反应后，使某些较小半径的孔隙变成可连通的，进而使砂岩介质的渗透系数整体变大；在物理化学渗流后期，由于压力和化学耦合作用，孔隙结构进一步演变，当压力梯度敏感度大于化学反应敏感度时，其渗透系数变大，反之变小。