Identification of Heterogeneity within Chalk for a Windfarm Development
On behalf of EDF EN, a French energy company, Geotek was commissioned to investigate how MSCL and X-ray could be used to identify heterogeneity within chalk formations
Identify flint clasts within chalk sub-samples using X-ray techniques
Identify heterogeneities within the chalk, using techniques on the MSCL
Could MSCL and X-ray data be established as a technique to identify areas where flint or heterogeneities within the core is present ahead of laboratory testing?
The chalk sub-samples were securely held within Geotek’s X-ray Computer Tomography machine (MSCL-XCT), which is specially designed and calibrated for core samples.
A Standard Multi-Sensor Core Logger (MSCL-S) was then used to acquire P-wave velocity and magnetic susceptibility data at 0.5 cm intervals through the core samples.
Chalk and flint have very similar densities, therefore 3D CT scanning was conducted in order to differentiate the flint clasts from the chalk matrix.
The CT scans also revealed lower relative density pockets within the flint possibly representing pockets of less cemented material.
The X-ray CT and MSCL data are able to image and identify flint clasts within chalk from elevated P-wave velocities and decreases in magnetic susceptibility. Furthermore, we were able to image small-scale heterogeneities within the chalk, which correlated with increased magnetic susceptibility.
These increases in magnetic susceptibility within the chalk could be used as a marker bed for future borehole correlation to determine stratigraphic elevation within the chalk sequence.
Increased magnetic susceptibility is indicative of an increase in magnetic minerals within the chalk, which could be used as a marker horizon for future studies.