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Simulations of the effects of proppant placement on the conductivity and mechanical stability of hydraulic fractures

International Journal of Rock Mechanics and Mining Sciences

Bolintineanu, Dan S.; Rao, Rekha R.; Lechman, Jeremy B.; Romero, Joseph A.; Jove Colon, Carlos F.; Quintana, Enrico C.; Bauer, Stephen J.; Ingraham, Mathew D.

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.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI

Using sampling moiré to extract displacement information from X-Ray images of molten salt batteries

Conference Proceedings of the Society for Experimental Mechanics Series

Reu, Phillip L.; Quintana, Enrico C.; Long, Kevin N.

Full-field axial deformation within molten-salt batteries was measured using x-ray imaging with a sampling moiré technique. This method worked for in situ testing of the batteries because of the inherent grid pattern of the battery layers when imaged with x-rays. High-speed x-ray imaging acquired movies of the layer deformation during battery activation. Numerical validation of the technique, as implemented in this paper, was done using synthetic and numerically shifted images. Typical results of a battery are shown for one test. Ongoing work on validation and more test results are in progress.

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TYPE Conference YEAR 2015
ScopusOSTIDOI
Results 26–50 of 70
Results 26–50 of 70