Time-Lapse Biogeomechanical Modified Properties of Ultra-Low Permeability Reservoirs

Abstract

This study introduces “biogeomechanics”, an emerging field of geotechnics, as a resourceful approach in assessing the impact of biological processes on the mechanical properties and behavior of geomaterials. Here, we investigated the localized and bulk mechanical properties and behavior due to interaction between microbes and ultra-low permeability reservoirs, using 2 types (containing artificially-induced and/or pre-existing natural fractures) of shale rock specimens; and 2 distinct microbial strains. We treated and cultivated the core specimens with the bacteria strains at distinct temperature, time, and growth conditions. Subsequently, we measured the near-term and long-term mechanical properties of the shale rock specimens impacted by the two distinct microbes. Our results indicated that over time, microbial actions on Eagle Ford and Marcellus shale rocks can: (1.) Enhance the localized (+\u200910% unconfined compressive strength, − 18% Poisson’s ratio,\u2009+\u200925% scratch toughness) and bulk (+\u200943% unconfined compressive strength, − 13% Poisson’s ratio) mechanical integrity; or (2.) Weaken the localized (− 20% unconfined compressive strength,\u2009+\u200925% Poisson’s ratio, -13% scratch toughness) mechanical integrity. Our findings in this study provide a novel insight into the temporal localized and bulk mechanical responses of ultra-low permeability formations with high heterogeneity, impacted by biological processes.