Probe Screening Techniques for Rapid, High-Resolution Core Analysis and Their Potential Usefulness for Energy Transition Applications

Abstract

Core analysis techniques have traditionally been used mainly for hydrocarbon reservoir applications. However, the same techniques are equally applicable to reservoir issues associated with energy transition, such as geothermal prospects, carbon geosequestration, and hydrogen storage. Traditionally, much core analysis has been performed successfully using core plugs. However, this approach has certain drawbacks: (1) the selected plugs may not necessarily be representative of the full range of lithologies, (2) key features (e.g., thin naturally cemented or fractured zones) may be missed, (3) high-resolution detail at the lamina scale may be missed, (4) depth shifting to well logs may not be sufficiently accurate, and (5) this strategy may be more sensitive to missing core. In this paper, we highlight the usefulness of probe core analysis techniques on slabbed core and powdered samples. For many reservoirs relevant to energy transition, it is crucial to have a high-resolution continuous record of petrophysical properties so that key features are not missed. Probe measurements are less destructive, without the need to cut core plugs, and provide: (1) high-resolution data at the lamina scale so that key features and small-scale heterogeneities can be identified, (2) improved depth matching to well-log data, and (3) rapid, cost-effective data. We describe examples highlighting some different probe techniques. While some techniques are well known, such as probe permeability, others, such as probe acoustics, probe luminance (from linear X-ray measurements), and probe magnetics, are less familiar to core analysts but are well suited for analyzing cores from reservoirs associated with energy transition as well as hydrocarbons. For example, potential geothermal prospects involve studying igneous and metamorphic samples (where the main radiogenic heat sources reside) as well as sedimentary samples, and differences in the magnetic susceptibility signals using a small, portable magnetic probe can quickly differentiate the different rock types. Probe acoustics can be used to (1) rapidly identify anisotropy by orienting the acoustic transmitter-receiver bracket in different directions, (2) identify open microfractures via longer transit times, and (3) produce high-resolution porosity profiles after correlation of transit times with some representative plug or well-log porosity data. Probe luminance and associated linear X-ray images, which are related to density, can indicate small-scale heterogeneities that may impact permeability variation and anisotropy and may not be seen from mere visual observations of the slabbed core surface.