: Coupled dissolution-precipitation reactions can alter the material properties of anisotropic, porous geologic media significantly. Effective development of subsurface geologic systems requires an understanding of how these reactions impact the reservoir. Here, we present the first study investigating the impact of dissolution-precipitation on the modified mechanical, storage, and transport properties of sedimentary rocks (shale, limestone, and dolomite). Experimental tests coupled with mechanical and geophysical approaches were used to quantify the altered rock properties and the degree of anisotropy. Microbial species are used to induce either isolated dissolution or precipitation reactions in each sample to remove competitive processes typically found in coupled biogeochemical dissolution-precipitation systems. Storage, transport, density, wave velocities ( V p , V s ), and dynamic elastic properties are quantified via coupled mechanical and geophysical approaches, and compared pre- and post-alteration. Dissolution reactions are shown to generally weaken rocks and increase permeability, with V p / V s increasing to final ratios of 1.8-2.0, while precipitation strengthens rocks and reduces permeability, with V p / V s trending toward 1.6-1.7. Poisson’s ratio ( ν ) is shown to significantly decrease during mineral precipitation, and increase during dissolution, and in both cases can approach the practical limits measured in geologic media. Intriguingly, measurements of V p / V s and ν suggest that the degree of anisotropy is altered during dissolution-precipitation reactions with transversely isotropic rocks becoming near- or quasi-isotropic. These results suggest that coupled subsurface reactions (e.g. geologic CO 2 storage, energy/waste storage applications) can significantly alter reservoir properties and degree of anisotropy, leading to a complex spatial-temporal redistribution of stress, deformation tensors, and fluid conductivity.
Schwartz et al. (Fri,) studied this question.