  We perform a series of repeated CO2 injections in a room-scale physical model
of a faulted geological cross-section. Relevant parameters for subsurface
carbon sequestration, including multiphase flows, capillary CO2 trapping,
dissolution, and convective mixing, are studied and quantified. As part of a
forecasting benchmark study, we address and quantify six predefined metrics for
storage capacity and security in typical CO2 storage operations. Using the same
geometry, we investigate the degree of reproducibility of five repeated
experimental runs. Our analysis focuses on physical variations of the spatial
distribution of mobile and dissolved CO2, multiphase flow patterns, development
in mass of the aqueous and gaseous phases, gravitational fingers, and leakage
dynamics. We observe very good reproducibility in homogenous regions with up to
97 % overlap between repeated runs, and that fault-related heterogeneity tends
to decrease reproducibility. Notably, we observe an oscillating anticline CO2
leakage behavior from an open anticline with a spill point in the immediate
footwall of a normal fault, and discuss the underlying causes for the observed
phenomenon within the constraints of the studied system.
