Perpustakaan Digital ITB

The growing global demand for energy and reliance on fossil fuels contribute to emissions, while Earth's temperature rise must be limited to below 1.5°C. Carbon Capture and Storage (CCS) offers a decarbonization strategy for safely storing CO2 underground. However, continuous CO2 injection leads to pressure build-up, inducing geomechanical risks, particularly rock failure due to shear stress. This study assesses rock failure in CO2 storage within a saline aquifer limestone formation, using the Mohr-Coulomb criterion and fracture pressure gradient to evaluate geomechanical risks. It also identifies key factors affecting rock failure and determines the effective storage capacity and percentage of each mechanism. A reservoir simulation of the static model was first conducted to determine a safe injection rate, based on the fracture pressure gradient of 0.7 psi/ft. An injection rate of 20 MMSCFD resulted in a maximum BHP of 2692.966 psi, well below the safety limit of 2732.48 psi (90% of BHP fracture). The base case simulation was then developed using pessimistic parameters to reflect the worst-case scenario. The 4D Coupling Geomechanics Simulation, based on the Mohr-Coulomb criterion (cohesion of 0 and angle of 30°), was performed with 20 years of continuous injection, resulting in rock failure throughout. A second simulation, using a minimum rock cohesion value of 0.1 MPa, showed no rock failure, establishing this new set of parameters as the best estimate for real-world applications. A sensitivity analysis was carried out using a Two-Factorial Design of Experiment (DOE) to assess the influence of key parameters on rock failure. The analysis considered three factors: injection rate, Young's modulus, and Poisson's ratio, with Well Block Pressure (WBP) as the response variable representing rock failure. The results show that the injection rate and Young's modulus are the most significant parameters affecting rock failure. This study emphasizes the importance of using representative geomechanical data, especially since Young's modulus plays a crucial role in rock failure. Based on the best estimate parameters, the effective storage capacity for injecting 20 MMSCFD of supercritical CO? with one injector well over 20 years is 146.1 BSCF, with trapping mechanisms comprising 73.2% structural trapping, 11.5% residual trapping, and 15.3% solubility trapping.