| Abstrakt: |
Shale is a highly heterogeneous and laminated formation that has the capability to swell and deform when coming into contact with high water activity fluids. The contemporary methods for characterizing the shale swelling, such as linear swelling meter (LSM) and strain gauges (SG), are limited to providing only the overall expansion of the ground shale material or shale specimens, which is insufficient for the complex characterization of shale–fluid interaction. Therefore, this work was focused on filling the gap in clay stabilizer performance evaluation by using the Digital Image Correlation (DIC) method, which introduces the dynamic quantitative analysis of complex tensile strain development, which is induced by the hydration and swelling of clay in the shale, along with the visualization of spatial variations in shale deformation. The experiments were carried out in atmospheric conditions by immersion of the shale specimens into the DI water and brines with various concentrations. The diverse effect of salt type and concentration on shale's swelling intensity, fracture initiation and propagation, and matrix alteration as a function of time was distinguished. From the full-field strain maps the induced local high strain-expansion sites and strain development in the matrix owing to shale–fluid interaction were identified. The X-ray diffraction (XRD) analysis was performed to correlate the mineralogical composition of the specimens to the shale's swelling response provoked by the DI water and brines. The anisotropy in shale swelling was evaluated, where the dominant expansion of the shale was found to be in the direction orthogonal to the bedding plane. Overall, the DIC allowed monitoring the mechanical alteration in the highly heterogeneous shale formation by the fluid intake, which provided a new understanding of a sophisticated shale behavior owing to clay expansion, whereby the swelling inhibition degree of shale by the brines was assessed. [ABSTRACT FROM AUTHOR] |
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