CO₂-enriched brine injection’s impact on mechanical properties of a sandstone specimen

¹ Ph.D. Student, Civil & Environmental Engineering Department, The University of Vermont, 33 Colchester Ave, Burlington, VT 05405, USA
² Associate Professor, Civil & Environmental Engineering Department, The University of Vermont, 33 Colchester Ave, Burlington, VT 05405, USA

^* Corresponding author: maziar.foroutan@uvm.edu

Abstract

CO₂ capture and geological sequestration is one of the most practical and efficient methods of mitigating anthropogenic CO₂ emissions. Due to the uncertainties associated with CO₂ injection into deep saline reservoirs, the interaction between the host rock and the injected CO₂ needs to be better understood as it can lead to considerable pore-structure changes. The geochemical reactions, especially mineral dissolution, can compromise the mechanical properties of the reservoir rock, which consequently threatens the reservoir stability and integrity. Therefore, it is crucial to capture the variation of mechanical properties of the reservoir rock upon CO₂ injection. In this study the variation of elastic properties (e.g. Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio) of a brine-saturated sandstone specimen upon injecting CO₂-enriched brine is investigated. The elastic properties of the specimen were initially characterized through multi-stage elastic (MSE) test before injecting the CO₂-enriched brine. Then, the synthetic brine solution was enriched with CO₂ and injected into the brine saturated sandstone specimen. The mechanical test results revealed that a significant mechanical weakening occurred upon injecting CO₂-enriched brine into the sandstone specimen. This mechanical degradation can be attributed to the dissolution of calcite and clay minerals. The results from this study indicated that the mechanical deterioration of reservoir rock during CO₂ injection should be considered through the entire CO₂ sequestration process (i.e. site selection, injection operation, and post-injection monitoring).