Determination of Diffusion Profiles in Altered Wellbore Cement Using X-ray Computed Tomography Methods

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• 作者：Harris E. Mason ; Stuart D. C. Walsh ; Wyatt L. DuFrane ; Susan A. Carroll
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：June 17, 2014
• 年：2014
• 卷：48
• 期：12
• 页码：7094-7100
• 全文大小：437K
• 年卷期：v.48,no.12(June 17, 2014)
• ISSN：1520-5851

文摘

The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining 鈥渆ffective linear activity coefficients鈥?(ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO₂-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment.