Collapse of reacted fracture surface decreases permeability and frictional strength

Peters, Catherine A.; Spokas, Kasparas
Issue date: 2018
Cite as:
Peters, Catherine A. & Spokas, Kasparas. (2018). Collapse of reacted fracture surface decreases permeability and frictional strength [Data set].
  author      = {Peters, Catherine A. and
                Spokas, Kasparas},
  title       = {{Collapse of reacted fracture surface dec
                reases permeability and frictional stren
  year        = 2018

Geochemical and geomechanical perturbations of the subsurface caused by the injection of fluids present the risk of leakage and seismicity. This study investigated how flow of acidic fluids affects hydraulic and frictional properties of fractures using experiments with 3.8 cm-long specimens of Eagle Ford shale, a laminated shale with carbonate-rich strata. In low-pressure flow cells, one set of samples was exposed to an acidic brine and another set was exposed to a neutral brine. X-ray computed tomography and x-ray fluorescence analysis revealed that samples exposed to the acidic brine were calcite-depleted and had developed a porous altered layer, while the other set showed little evidence of alteration. After reaction, samples were compacted and sheared in a triaxial cell that supplied normal stress and differential pore pressure at prescribed sliding velocities, independently measuring friction and permeability. During the initial compaction, the porous altered layer collapsed into fine particles that filled the fracture aperture. This effectively impeded flow and sealed the fracture, resulting in a decrease in fracture permeability by 1 to 2 orders of magnitude relative to the compressed unaltered fractures. During shear, the collapsed layer of fine-grained particles prevented the formation of interlocking micro-asperities resulting in lower frictional strength. With regard to subsurface risks, this study showcases how coupled geochemical and geomechanical processes could favorably seal fractures to inhibit leakage, but also could increase the likelihood of induced seismicity. These findings have important implications for geological carbon sequestration, pressurized fluid energy storage, geothermal energy, and other subsurface technologies.

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Five 3D X-ray computed tomography images of Eagle Ford shale rock coupon pairs, one for each condition shown in Figure 3 in the related publication. Details of the data in this part are presented in README.txt. For more information about the experiments and methodology, please refer to related publication.

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# Filename Description Filesize
1 README.txt 739 Bytes
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3 10.2 GB
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6 9.29 GB