Hydro-mechanical-electrical simulations of synthetic faults in two orthogonal directions with shear-induced anisotropy

Fluid flow in fractures controls subsurface heat and mass transport,which is essential for developing enhanced geothermal systems and radioactive waste disposal.Fracture permeability is controlled by fracture microstructure(e.g.aperture,roughness,and tortuosity),but in situ values and their anisotropy have not yet been estimated.Recent advances in geophysical techniques allow the detection of changes in electrical conductivity due to changes in crustal stress and these techniques can be used to predict subsurface fluid flow.However,the paucity of data on fractured rocks hinders the quantitative interpretation of geophysical monitoring data in the field.Therefore,considering different shear displacements and chemical erosions,an investigation was conducted into the hydraulic-electric relationship as an elevated stress change in fractures.The simulation of fracture flows was achieved using the lattice Boltzmann method,while the electrical properties were calculated through the finite element method,based on synthetic faults incorporating elastic-plastic deformation.Numerical results show that the hydraulic and electrical properties depend on the rock's geometric properties(i.e.fracture length,roughness,and shear displacement).The permeability anisotropy in the direction parallel or perpendicular to the shear displacement is also notable in high stress conditions.Conversely,the permeability econductivity(i.e.,formation factor)relationship is unique under all conditions and follows a linear trend in logarithmic coordinates.However,both matrix porosity and fracture spacing alter this relationship.Both increase the slope of the linear trend,thereby changing the sensitivity of electrical observations to permeability changes.

Mass balance of saline lakes considering inflow loads of rivers and groundwater: the case of Lake Issyk-Kul, Central Asia

This study aimed to elucidate the influence of inflow water on the salinity concentration process of a saline lake and the mass balance of Lake Issyk-Kul,a tectonic saltwater lake in Kyrgyzstan.Based on the survey results and meteorological data from 2012 to 2015,we analyzed the dissolved chemical composition loads due to water inflow.Then,we discussed the relationship between the increase in salinity and water inflow into the lake.Through the water quality analysis data,we used the tank model to estimate the river inflow and analyze the loads by the L-Q curve.The groundwater loads were then estimated from the average annual increase in salinity of the lake over a period of 30 a.The results suggest that Lake Issyk-Kul was temporarily freshened between about AD 1500 and 1800 when an outflowing river existed,and thereafter,it became a closed lake in AD 1800 and continued to remain a saline lake until present.The chemical components that cause salinization are supplied from the rivers and groundwater in the catchment area,and when they flow into the lake,Ca^(2+),HCO_(3)−and Mg^(2+)precipitate as CaCO_(3) and MgCO_(3).These compounds were confirmed to have been left on the lakeshore as evaporite.The model analysis showed that 1.67 mg/L of Ca^(2+)and Mg^(2+)supplied from rivers and groundwater are precipitated as evaporite and in other forms per year.On the other hand,salinity continues to remain in the lake water at a rate of 27.5 mg/L per year.These are the main causes of increased salinity in Lake Issyk-Kul.Since Na^(+)and Cl^(-)are considered to be derived from geothermal water,they will continue to flow in regardless of the effects of human activities.Therefore,as long as these components are accumulated in Lake Issyk-Kul as a closed lake,the salinity will continue to increase in the future.