Dual Energy CT Scanning

A Millimeter-Scale Log for Cored Intervals

Speaker

Mr. AJ Kumar
Global Manager – Digital Rock Services
Core Laboratories

Abstract

Rapid, non-destructive screening using high-definition imaging techniques now provides a viable solution for superior visualization and detailed quantitative core assessment. These detailed deliverables are available before the core is removed from the inner core barrel and other measurements are commenced. X-ray scanners, popularly known as Computed Tomography (CT) scanners are used for such qualitative and quantitative description of cores. Similar to medical applications, CT scanners are used to capture the entire three-dimensional aspect of rocks when they arrive from wellsite.

CT scanning is performed early-on, before cores are extruded and handled, making it indispensable from a reservoir state preservation perspective. This digital preservation helps in visualization and assessment of cores at any point in time, months or years after the cores are acquired.

Newer and advanced CT scanners have capabilities to quickly scan objects at more than one energy level. Dual Energy CT scanning of cores provides information on density and atomic number at a millimeter-scale, vertically. When combined with extensive laboratory physical measurements, high-resolution bulk density and photoelectric factors are quantified. Unique cluster analysis of these data combined with core databases encompassing global lithotypes, result in a solid interpretation of core mineralogy and therefore, a mineralogy log for the cored intervals. Availability of vast core data enables robust empirical approach of quantification of strength profile and dynamic mechanical properties at millimeter-scale for the cored intervals. Strength index at such high resolution, in conjunction with CT-based acoustic velocities helps quickly assess and refine lateral landing zones in a well.

Additionally, applications of dual energy CT include, detailed fracture description, orientation of cores without physically scribing cores, enhanced sub-sample selection, porosity etc. They are also used to correct downhole logs where resolution is typically coarser than what’s captured with CT.

The early time capture of data and quick interpretation of properties via these methods make dual energy CT scanning of cores, a vital part of core analysis programs.

Biodata

AJ Kumar is director of the digital rock characterization group in the Petroleum Services division of Core Laboratories, and is based in Houston, TX. He completed his MS in Engineering with a thesis on diffusion dependency on permeability of CBM reservoirs. For last 9 years, AJ has been working with Core Laboratories in a variety of lead technical roles and established state-of-the-art laboratories.