Geochemical reactions altering the mineralogical and multiscale pore characteristics of uranium-bearing reservoirs during CO2 + O2in situ leaching

Abstract

CO2 + O2in situ leaching has been extensively applied in uranium recovery in sandstone-type uranium deposits of China. The geochemical processes impact and constrain the leaching reaction and leaching solution migration; thus, it is necessary to study the CO2 + O2–water–rock geochemical reaction process and its influence on the physical properties of uranium-bearing reservoirs. In this work, a CO2 + O2–water–rock geochemical reaction simulation experiment was carried out, and the mineralogical and multiscale pore characteristics of typical samples before and after this simulation experiment were compared by X-ray diffraction and high-pressure mercury intrusion porosimetry (HPMIP). The results show that the CO2 + O2–water–rock geochemical reaction has complicated effects on the mineral compositions due to the various reaction modes and types. After the CO2 + O2–water–rock geochemical reaction, the femic minerals decrease and the clay minerals in the coarse sandstone, medium sandstone, fine sandstone, and siltstone increase, while the femic minerals and clay minerals in sandy mudstone show a contrary changing trend. The CO2 + O2–water–rock geochemical reaction decreases the total pore volume of uranium-bearing reservoirs and then promotes pore transformation from small scale to large scale. The fractal dimensions of macropores are decreased, and the fractal dimensions of mesopores, transition pores, and micropores are increased. The effects of felsic mineral and carbonate dissolution, secondary mineral precipitate, clay mineral swelling, and mineral particle migration are simultaneously present in the CO2 + O2in situ leaching process, which exhibit the positive transformation and the negative transformation for the uranium-bearing reservoirs. The mineral dissolution may improve reservoir permeability to a certain degree, while the siltation effect will gradually reveal with the extension of CO2 + O2in situ leaching. This research will provide a deep understanding of the physical property response of uranium-bearing reservoirs during CO2 + O2in situ leaching and indicate the direction for the efficient recovery of uranium resources.

Experimental and Numerical Simulation Research on Controllable Shock Wave-Induced Shale Fracturing under Repeated Action

“…Reservoir stimulation can be roughly divided into chemical transformation and physical transformation. − Chemical transformation refers to the use of injected solutions to react with the reservoir to increase its permeability. , This process is limited by the mineral composition of the reservoir when it is applied on-site. On the other hand, physical stimulation involves applying pressure to induce damage and fractures in the reservoir, thereby increasing its permeability .…”

The chemical damage of sandstone after sulfuric acid-rock reactions with different duration times and its influence on the impact mechanical behaviour

“…The proportion of supply and demand of natural uranium is seriously unbalanced, and the dependence on imports remains high [ 2 , 3 ]. Therefore, there is an urgent need to increase the production capacity of natural uranium and the self-sufficiency rate of uranium resources, aiming to ensure energy security and accelerate the construction of a nuclear industry powerhouse [ 4 , 5 ].

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Investigation of the Impact of Leaching Agent Concentration and pH on the Stability of Agglomeration of Ion-Absorbed Rare Earth Deposits

“…The cementation effect generated by Ca 2+ inhibits the dissolution of calcareous cement and clay mineral production in the soil [23], raising the charge on the soil surface and the ion exchange between Na + , K + , and solution Ca 2+ [24], thus increasing the interparticle affinities and the tight conjunction of particles that induce smaller soil pores, tighter particles, and stabler soil structures. Wang et al showed that during the leaching process, complex chemical reactions occur, causing changes in the pore structure within the ore body [25][26][27]. Hu et al found that the electrostatic repulsive force is affected by various factors, including the type of electrolyte, concentration, pH, and others [28,29].…”