Experimental Study on Pressure Gradient-Viscosity-Chemical Coupling Seepage Law of Low-permeability Sandstone Uranium Ore Rock

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 permeability test device. The 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 whole rock voids and the rock permeability on the whole 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, which 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 structure further evolves. When the pressure gradient is more sensitive than chemical sensitivity of reaction, the permeability coefficient increases, whereas decreases.