The Geometry and Hydraulic Properties of Fractured Rocks from Particle Transport Measurements in Pumped Wells

Recently developed hydraulic equations that govern the transport of particles through fractured and coarse granular aquifers provide great insights into the geometry and hydraulic properties of fractured and porous rocks. These equations have many applications, but are particularly useful in the analysis of fractured rocks using elapsed time-particle measurements during single well pumping tests. The turbidity responses determine whether the fracture network is planar or orthogonal, whether it is uniform, the (flow path) capture radius of the well, rock matrix filtration, and the hydraulic conductivity, transmissivity and percentage of flow through the porous matrix of the rock. Particle size distribution measurements against time can be used to determine the flow velocity in the fractures at any radius from the well from the mobile particle sizes. These measurements can be combined with classical time-drawdown data that reveal the single fracture, karst conduit, dual permeability components and homogeneity of the fracture network to compile a single, double or triple permeability hydraulic conceptual model with detailed characterization of the fracture network and solution widened features. As particles are mobile in rock fractures but are filtered out by porous media and porous matrix blocks; and mobile particles transport many harmful compounds that are otherwise immobile through adsorption, attachment, and ion exchange; bacteria, heavy metals, carbon compounds with low partition coefficients (e.g., PAHs) and radionuclides; resolution of the fracture network and the particle transport therein is the key to success. It is therefore essential to undertake particle measurements as a key data set, especially as the cost is low and the benefit is high, to determine the characteristics of the fractured media; the rates and constraints of the particle transport in the fractured media, and the transport constraints and rates of the compounds transported by the particles.

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