Micro-CT for Digital Rock Analysis

Micro-CT scanners are able to perform X-ray imaging of core sub-samples from 10 to 500 times higher resolution than macro-CT scanners, known as medical CT scanners. Scan resolution is generally guided by the size of the sample, so the smaller the sample, the higher the resolution.
A 25-micrometer resolution sub-sample scan (a standard test plug) is being used in the sample selection process for sophisticated reservoir-condition flow studies.
Small features (e.g., micro fractures, small vugs, anomalies, etc.) are hard to visualize with macro-CT imaging but are captured well with micro-CT scanners. Primarily, these scans are used as an advanced screening tool for high-value testing. However, scan data bring extraordinary value for quantifying varying phases in plug samples (e.g., salt crystal locations, location of asphaltene, distribution of fluids, etc.) for assessment of their impacts on porosity, permeability and flow behavior. Fracture propagation as a result of increasing vertical stress on rocks also can be visualized.
LOTUS-NDT Micro-CT scans at higher pore-scale resolutions help resolve features as small as 1 micrometer. Image acquisition and segmentation at such resolutions aid in grain and pore system characterization. When consolidated with appropriate and extensive physical measurements, petrophysical data such as permeability, capillary pressure and electrical properties are quantified. Confidence in modeling petrophysical data is improved using models calibrated to laboratory measurements. Imaging and quantification of these properties also are ideal for friable to unconsolidated samples and large-sized drill cuttings or when core recovery is poor. The rock-based digital physically constrained models provide data that correlate well to conventional core analyses.

Sandstone Oil Plug, 2D Axial microtomographic image by LOTUS-NDT.
Sandstone Oil Plug, 2D Axial microtomographic image by LOTUS-NDT.