Abstract — .
Abstract — .
Abstract — Storing CO2 in depleted hydrocarbon reservoirs is a common practice world-wide. Mudrocks often serve as seals above these reservoirs due to their small pore throats and low permeability, but they can fail if the buoyant pressure of the trapped fluid overcomes the threshold pressure of the seal. Mudrocks are primarily made of silt-sized and clay-sized particles, and sufficiently high silt concentrations can create situations where the silt grains create a connected stress chain through the rock matrix, which preserves the large pore throats under compaction. This phenomenon, termed silt bridging, can reduce the threshold pressure of the mudrock, causing seal failure. We used grain-scale modeling to create computer-generated grain packs with and without the effect of gravity to understand the effects of deposition and compaction on the petrophysical properties like capillary pressure, tortuosity, permeability, capillary drainage curves, and spatial correlation of heterogeneities. We found that, when the fraction of silt-sized grains exceeded 40%, the percolation length (the length of the first path of the non-wetting fluid through a medium) and the tortuosity suddenly decreased. This was supported by the results from the throat size variograms, where the same type of correlations between throats were observed at greater lag distances, signifying increased intergranular distances. Our work provides an insight into the role of different grain sizes, concentrations and spatial distributions on the flow properties and sealing capacity of mudrocks.