Mechanistic Study of Microbial Altered Properties in Dolostones

In this study, a suite of tests was conducted to investigate the microscale mechanical, elastic, and microstructural alterations due to rock–microbial interactions in dolomitic rocks (dolostones) at elevated treatment (temperature and pressure) conditions. Dolostone samples were treated with a microbial media, and the microscale mechanical and elastic responses and the unit weight changes due to the rock–microbial interaction in dolotstones were quantified. Subsequently, a new relationship for estimating dynamic Young’s modulus (E) of rocks from scratch test was proposed. The microstructural alteration during the process was reported using scanning electron microscopy (SEM). The results of rock–microbial interactions in dolostone indicate potential: (i) mechanical alterations with distinct low and peak values in investigated core samples; (ii) enhancement in mechanical and elastic properties and the mechanical integrity (−37% Poisson’s ratio, ν; +320% scratch-derived Young’s modulus, E_scr; +80% unconfined compressive strength, UCS; +223% scratch toughness, K_s); (iii) increase in pore throat clogging and unit weight (+ 33%) due to mineral precipitations, which can occlude and cement the pore spaces in dolostones and increase the intergranular-bonding integrity. The results also suggest a greater rock–microbial impact in dolostones relative to shales, due to higher inherent pores and permeable fractures in dolostones which might have accelerated microbial actions at farther reach. Further, this study provides new insights into understanding the coupled rock–microbial interaction in dolostones, and proposes E_scr as an alternate method for estimating the Young’s modulus of sedimentary rocks from scratch tests.