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We generate a wide range of models of proppant-packed fractures using discrete element simulations, and measure fracture conductivity using finite element flow simulations. This allows for a controlled computational study of proppant structure and its relationship to fracture conductivity and stress in the proppant pack. For homogeneous multi-layered packings, we observe the expected increase in fracture conductivity with increasing fracture aperture, while the stress on the proppant pack remains nearly constant. This is consistent with the expected behavior in conventional proppant-packed fractures, but the present work offers a novel quantitative analysis with an explicit geometric representation of the proppant particles. In single-layered packings (i.e. proppant monolayers), there is a drastic increase in fracture conductivity as the proppant volume fraction decreases and open flow channels form. However, this also corresponds to a sharp increase in the mechanical stress on the proppant pack, as measured by the maximum normal stress relative to the side crushing strength of typical proppant particles. We also generate a variety of computational geometries that resemble highly heterogeneous proppant packings hypothesized to form during channel fracturing. In some cases, these heterogeneous packings show drastic improvements in conductivity with only moderate increase in the stress on the proppant particles, suggesting that in certain applications these structures are indeed optimal. We also compare our computer-generated structures to micro computed tomography imaging of a manually fractured laboratory-scale shale specimen, and find reasonable agreement in the geometric characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Highly conductive polymers are difficult to process utilizing standard polymer approaches. This report describes a polymer composite loaded with a eutectic metal that is molten during melt processing along with a more traditional Nickel particulate filler. Conductivities over 300 S/cm were achieved, and 60 vol% metals loading was processable with a single screw extruder. The addition of the Nickel particulate was critical for maintaining eutectic dispersion. We anticipate that this approach will facilitate the implementation of conductive polymers into a broader variety of practical applications, due to the enhanced compatibility with standard polymer processing techniques such as extrusion, melt mixing, and resin transfer-molding operations. [Copyright &y& Elsevier]