Development of in-situ permeability testing system for low-permeability sandstone-type uranium deposits

Rapid and accurate in-situ permeability testing is extremely important during the in-situ leaching of low-permeability sandstone-type uranium deposits. The current permeability testing methods rely on laboratory tests and the inversion of core or debris samples, which cannot reflect the true permeability of uranium deposits under their occurrence conditions. Therefore, this paper proposes a testing device based on the pressure pulse method for the in-situ permeability and corresponding automatic calculation software, and establishes the testing process. Specimen tests on a concrete model are carried out, and the testing results show consistency with the laboratory results and the micro-seepage numerical simulation results of uranium deposit cores in terms of magnitude and governing laws. However, due to factors such as the specimen tests not considering confining pressure, the uneven pouring, and the local cracking of the specimen caused by pulse pressure, the measured permeability deviation is between 7.14% and 21.47%. The permeability test results are related to the mineral stacking structure, the testing system, and the testing process. The permeability of uranium deposits with local gravel and basal cementation mode is relatively small. The main factors affecting the permeability test results are the deformation and friction of the high-pressure water storage tank and cable, the loose connection of various components, the integrity of the wellbore casing or the wellbore wall, and the installation position of the measuring section system. This study presents a rapid and accurate insitu permeability testing technology for low-permeability sandstone-type uranium deposits, providing technical support for site selection and effect prediction in in-situ learning.