| dc.description.abstract | The world is in need of a shift to cleaner energy, and carbon storage is expected to be an important part of the transition. Geological carbon storage is a process in which captured carbon dioxide (CO2) is injected into the subsurface for storage. There are several trapping mechanisms operating at different timescales which prevents the CO2 from leaking back to the surface. Saline aquifers, which are reservoirs filled with formation brine, are good options for storage as they offer high storage capacity. A problem when storing CO2 in such reservoirs is that the salinity in the brine can cause salt to precipitate, when water evaporates into the CO2, which can effect injectivity. Documentation of numerical and experimental research have demonstrated that precipitation can alter porosity, permeability and affect injectivity during CO2 storage.
This project investigated how the degree of heterogeneity affected the spatial distribution of salt precipitation during CO2 injection. Numerical simulations were performed using OPM Flow, and two models were utilized. First, a 3D model where results were plotted in 2D with a focus near the injection well. To plot the 2D results, provided configuration files were utilized, which set the simulations and created input files. Several runs were simulated with different permeabilities, as well as different orders and numbers of layers. Half of the runs were simulated with salt precipitation included and half of the runs with it excluded, to compare the distribution of the injected CO2. In the second model, two homogeneous cases based on the 2D geometry of the SPE CSP 11B benchmark model were simulated. One case with salt precipitation was compared to one without salt precipitation.
The results demonstrated that in homogeneous and slightly heterogeneous systems, greater blockage occurred next to the injection well. This affected injectivity of CO2 into the layers where salt had clogged the well. A higher bottom hole pressure when compared to more heterogeneous runs was also observed. When the degree of heterogeneity was large, salt precipitated in the high permeability layers. As they provide better flow capacities, capillary backflow had a better effect in these layers. The homogeneous runs provided unexpected locations of the dry-out zone, which could be because of errors in the numerical simulations. More studies could be performed to investigate the effect on CO2 distribution with temperature variations. Additionally, studies on varying degrees of heterogeneity in the 3D grid of the SPE CSP 11C benchmark model could be conducted. | |
