Presentation Description
Objectives and Scopes
For CO2 geologic storage projects, faults present potential leakage risks. To better understand fluid flow behavior in and around faults, a shallow CO2 controlled release field project will be conducted at the CO2CRC Otway International Test Centre by injecting into the Brumbys Fault. In order to de-risk the field project, in this study we conducted several sand tank experiments to model and validate field-scale simulation results prior to project commencement.
For CO2 geologic storage projects, faults present potential leakage risks. To better understand fluid flow behavior in and around faults, a shallow CO2 controlled release field project will be conducted at the CO2CRC Otway International Test Centre by injecting into the Brumbys Fault. In order to de-risk the field project, in this study we conducted several sand tank experiments to model and validate field-scale simulation results prior to project commencement.
Methods, Procedures, and Process
CO2 will be injected at 60m below ground near the fault zone of the shallow Brumbys Fault. To replicate the field geologic pattern in the lab setting, we mixed different grain sizes of glass beads so that their capillary entry pressure ratios are equivalent to the permeability ratios measured for the various layers. We then manually packed the sand tank domain according to a 2D cross-section from the field-scale simulation domain shrunk to the size of the tank. Finally, we conducted buoyancy-driven fluid flow experiments at ambient conditions using different analog fluids and compared the results with field-scale simulations.
CO2 will be injected at 60m below ground near the fault zone of the shallow Brumbys Fault. To replicate the field geologic pattern in the lab setting, we mixed different grain sizes of glass beads so that their capillary entry pressure ratios are equivalent to the permeability ratios measured for the various layers. We then manually packed the sand tank domain according to a 2D cross-section from the field-scale simulation domain shrunk to the size of the tank. Finally, we conducted buoyancy-driven fluid flow experiments at ambient conditions using different analog fluids and compared the results with field-scale simulations.
Results, Observations, Conclusions
According to the results of the air/water experiments, once air (representing gaseous CO2) enters the high-permeability fault, it rapidly migrates upward due to high buoyancy forces and accumulates underneath the capping clay layer. Therefore, the highest CO2 saturation is expected to occur near the top of the fault, consistent with the field-scale simulation results. Even when the injection point is moved farther away from the fault, there is still a high chance that the injected gas would enter into the fault zone. Further experiments with a different analog fluid pair (Soltrol 220/glycerol-water mixture) have demonstrated that the fault leakage behavior is likely to be similar even when occurring at depth where CO2 is a supercritical fluid.
According to the results of the air/water experiments, once air (representing gaseous CO2) enters the high-permeability fault, it rapidly migrates upward due to high buoyancy forces and accumulates underneath the capping clay layer. Therefore, the highest CO2 saturation is expected to occur near the top of the fault, consistent with the field-scale simulation results. Even when the injection point is moved farther away from the fault, there is still a high chance that the injected gas would enter into the fault zone. Further experiments with a different analog fluid pair (Soltrol 220/glycerol-water mixture) have demonstrated that the fault leakage behavior is likely to be similar even when occurring at depth where CO2 is a supercritical fluid.
Significance/Novelty
Fault leakage is just one area of concern for CO2 storage projects, and sand tank experiments provide a low-cost, visual, and dynamic way to validate field-scale simulation results before the projects start, hence boosting confidence and reducing risk. The sand tank experimental methods can also be applied to study various other aspects of CO2 storage such as how heterogeneities, dip angles, and injection scenarios affect plume spread and stabilization, helping to further de-risk CO2 geologic storage.
Fault leakage is just one area of concern for CO2 storage projects, and sand tank experiments provide a low-cost, visual, and dynamic way to validate field-scale simulation results before the projects start, hence boosting confidence and reducing risk. The sand tank experimental methods can also be applied to study various other aspects of CO2 storage such as how heterogeneities, dip angles, and injection scenarios affect plume spread and stabilization, helping to further de-risk CO2 geologic storage.