Quantitative characterizations of anisotropic dynamic properties in organic-rich shale with different kerogen content

Understanding the quantitative responses of anisotropic dynamic properties in organic-rich shale with different kerogen content (KC) is of great signi ficance in hydrocarbon exploration and development. Conducting controlled experiments with a single variable is challenging for natural shales due to their high variations in components, diagenesis conditions, or pore fluid. We employed the hot-pressing technique to construct 11 well-controlled arti ficial shale with varying KC. These arti ficial shale samples were successive machined into prismatic shape for ultrasonic measurements along different directions. Observations revealed bedding perpendicular P-wave velocities are more sensitive to the increasing KC than bedding paralleling velocities due to the preferential alignments of kerogen. All elastic stiffnesses except C-13 are generally decreasing with the increasing KC, the variation of C-11 and C-33 on kerogen content are more sensitive than those of C(44 )and C-66 . Apparent dynamic mechanical parameters ( n and E ) were found to have linear correlation with the true ones from complete anisotropic equations independent of KC, which hold value towards the interpretation of well logs consistently across formations. Anisotropic mechanical parameters ( Delta E and brittleness Delta B ) tend to decrease with the reducing KC, with Delta B showing great sensitivity to KC variations. In the range of low KC ( <10%), the V-P /V(S )ratio demonstrated a linearly negative correlation with KC, and the V-P /V-S ratio magnitude of less than 1.75 may serve as a signi ficant characterization for highly organic-rich ( >10%) shale, compilation of data from natural organic rich-shales globally veri fied the similar systematic relationships that can be empirically used to predict the fraction of KC in shales. (c) 2023 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).