Determination of diffusion profiles in altered wellbore cement using X-ray computed tomography methods.

Area of Science:

• Geochemistry
• Materials Science
• Petrophysics

Background:

• Accurate wellbore integrity models require understanding chemical and mechanical changes in hardened Portland cement.
• X-ray computed tomography (XRCT) offers a non-destructive 3D imaging method to study these changes.

Purpose of the Study:

• To develop a method for extracting subvoxel mineralogical and chemical information from XRCT images.
• To improve geochemical and mechanical models of cement alteration in wellbore environments.

Main Methods:

• Combining advanced image segmentation with geochemical models of cement alteration.
• Determining effective linear activity coefficients (ELAC) for white light sources to create calibration curves.
• Relating image grayscales to material composition for detailed analysis.

Main Results:

• Successfully extracted subvoxel mineralogical and chemical data from XRCT images.
• Identified discrete increases in calcium concentration at reaction boundaries during cement alteration by CO2-rich brine.
• Generated a data set supporting the modeling of cement alteration.

Conclusions:

• The developed XRCT method provides detailed insights into cement alteration processes.
• The findings contribute to improved predictive models for wellbore integrity.
• This approach advances the understanding of geochemical and mechanical interactions in wellbore environments.