Dual Energy CT (DECT) provides the Petrophysicist/Core Analyst with additional measurements beyond the single energy attenuation 3d maps. Scanning rocks at two different energies and then solving some calibrated X-ray attenuation equations for rock properties - effective atomic number (Zeff) and density - can be cross-plotted and mapped to identify lithologies, facies and predominant rock chemistry. We introduced this technology in the nineties and have continued development of our software and continued to improve procedures and methodologies since then.
As depicted in the diagram below, the whole core or a plug is scanned at high and low energy yielding two volumes which are passed through our attenuation algorithms to produce two output volumes, Zeff and Density. Using a cross-plot 3d histogram of these two properties, the analyst interactively identifies the chemistry/lithology of the rock. Depth values are taken, and a log and slab of each property is plotted alongside a color-mapped "slab". With a cross-plot of thetwo properties, the predominant pairs populations are used to indicate facies in the formation.
Currently there are CT scanners which produce both energies in one pass. It possible two achieve this by scanning twice with good table control repetition without causing registration problems, so single energy scanners can be employed.
We have the most expert and tried and true methods for obtaining accurate results through best practices and the precision calibration which is absolutely required. Please contact us for assistance in employing this technology, whether you a just evaluating its benefits, have purchased software, a CT scanner, or desiring to optimize your existing software/hardware DECT system. We would be glad to provide a list of scientific paper references on this technology.
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