3D Quantitative Prediction of the Groundwater Potential Area-A Case Study of a Simple Geological Structure Aquifer.

The Ordos Basin is a sedimentary basin located in Inner Mongolia, China, where coal and uranium coexist. Water inrush disasters have always been one of the main disasters that threaten the safety of coal mine production, and thus, the study and division of groundwater potential regions are of great significance for the prevention of water inrush disasters and in situ leaching of sandstone-type uranium ore. A new method combining truncated Gaussian simulation and sedimentary facies control was established to predict the groundwater potential area. Taking a typical aquifer, the Zhiluo Formation, as an example, based on high-resolution sequence stratigraphy, geophysics, sedimentary geology, and geostatistical theory, the plane distribution of sand bodies was predicted. Furthermore, the relationship between rock porosity and electricity porosity was established to calculate the regional porosity. Combined with truncated Gaussian simulation and facies-controlled modeling methods, a facies-controlled heterogeneous property model was established to analyze the heterogeneous effective porosity of the aquifer in the study area. Groundwater potential areas were quantitatively evaluated by 3D modeling analysis. The results of the evaluated model were verified by actual data and provide a geological guarantee for the accurate mining of deep coal and uranium ore. A 3D distributed model of chemical elements, which is meaningful for in situ leaching uranium mining, is expected in future research.

Facies-Controlled Geostatistical Porosity Model for Estimation of the Groundwater Potential Area in Hongliu Coalmine, Ordos Basin, China.

Accurate and reliable evaluations of potential groundwater areas are of significance in the hydrogeological assessments of coalfields because water inrush disasters may be caused by unclear groundwater potential. A three-dimensional geological model of porosity based on deterministic modeling and a facies-controlled method are used to determine the groundwater potential of the coal measure aquifer. The modeling processes are as follows: based on the interlayer and discontinuity (faults) data extracted from boreholes and geological maps, an integrated sequence framework model is developed. Using the results of sedimentary microfacies identification and the method of deterministic modeling, a sedimentary microfacies model is successfully established. Finally, based on facies-controlled and sequential Gaussian methods, an effective porosity model is established that can predict the groundwater potential. The predicted results show that sandstones sedimented in channel, point bar, and batture environments possess high effective porosity and strong groundwater potential; however, the sandstones sedimented in interdistributary bays, flood plains, and sand sheets possess low effective porosity. Model validation was performed based on the hydrological pumping test data collected from observation boreholes, drainage water inflow data from dewatered boreholes in the tunnel around workface, and the mine water inflow in tunnels and the workfaces. The validation analysis results show that the effective porosity and sedimentary facies were correlated with the actual flux. The predicted results are consistent with the actual flux data, validating the predicted model.

Hydrogeochemistry of Water in Coal Measures during Grouting Treatment of Taoyuan Mine, China.

Permian coal measure sandstone fissure water (referred to as "coal measure water," that is, water in coal measures) is one of the important water sources for industrial and agricultural activities in mining areas. However, the regional high-pressure grouting, one of the most widely used floor control methods, may affect the coal measure water which is connected with limestone aquifer. This study used Taoyuan mine, a typical coal mine in Huaibei coalfield, as the research area to study the influencing mechanism of a grouting treatment on the hydrogeochemical evolution of coal measure water. The hydrogeochemical characteristics and water-rock interaction mechanism of the coal measure water before and during the treatment were evaluated using a Piper trigram, ion combination ratio, and hydrogen-oxygen stable isotope. The anions and cations in the coal measure water before and during the treatment had the same trends at SO4 2-  > HCO3 -  > Cl- and Na+ > Ca2+ > Mg2+ , respectively. Hydrochemical types of coal measure water before treatment were mainly SO4 ·Cl-Ca·Mg, SO4 ·Cl-Na, and HCO3 -Na, and during treatment they were mainly SO4 ·Cl-Na and HCO3 -Na. The formation of chemical components of coal measure water before treatment was mainly caused by carbonate dissolution, sulfate dissolution, and pyrite oxidation. During the treatment, sulfate dissolution and pyrite oxidation were the main geochemical processes, and ion exchange was enhanced. Atmospheric precipitation was the source of all water samples, and all showed an obvious 18 O drift.

The experimental study of fluorine-leaching ability of granite with different solutions: A new insight into the dynamic of groundwater fluorine levels along coastal zones.

Drinking-water fluorosis is universal along coastal zones, and the seawater or brine water intrusion is occasionally supposed to enrich groundwater fluorine levels. However, there is no conclusive proof, and the laws and mechanisms remain ambiguous. Granite, the common fluorine-bearing rock, is selected and experimented upon to reveal the characteristics and laws of fluorine's leaching ability during the intrusion of seawater. The fluorine-leaching ability increases with the increasing ratios of seawater or brine water, the increasing levels of NaCl or NaHCO3, and the decreasing levels of CaCl2. Such results directly confirm that seawater or brine water intrusion, as well as the conditions of higher Na+, HCO3- and lower Ca2+, promotes fluorine-leaching ability from granite. The intensities of SiOSi, SiOFe, SiOAl bonds decrease but those of OH bonds increase with a higher ratio of seawater or brine water, the higher levels of NaCl or NaHCO3, and the lower levels of CaCl2. This indicates the more silicate dissolution and stronger OH-F exchange evoked by seawater or brine water intrusion are responsible for the higher fluorine-leaching from granite. Therefore, the process of seawater or brine water intrusion should be important for the groundwater enrichment dynamics along coastal zones.