Pore structure of sediments from Green Canyon 955 determined by mercury intrusion

We used mercury injection capillary pressure measurements to characterize the pore structure of three channel-levee lithofacies (sandy silt, dayey silt, and silty day) from the gas hydrate reservoir in Green Canyon Block 955 in the northern Gulf of Mexico. We compared measurements on both depressurized and reconstituted samples and also made comparisons across the different lithofacies. Comparison between depressurized and reconstituted sandy silt samples indicated that the displacement pressures, porosities, percolation thresholds, and pore volume fractal dimensions were not statistically different between the two sample sets, suggesting that resedimentation is an effective method for recreating intact sample fabric. The modal pore radii corresponding to the peaks in the poresize distributions were 4.56 +/- 0.52 mu m for sandy silt, 0.0610 +/- 0.0080 mu m for dayey silt, and 0.0326 +/- 0.0039 mu m for silty day. We found that the Thomeer capillary drainage curve model better represented the measurements than the van Genuchten model. The displacement pressures for methane gas displacing water were 0.0144 +/- 0.0034 MPa for sandy silt, 1.30 +/- 0.15 MPa for dayey silt, and 2.72 +/- 0.13 MPa for silty day (errors reported as +/- 1 standard deviation). Based on the measured pore-size distributions, we found that the maximum hydrate saturation in the sandy silt layers is controlled by limitations on methane transport and not by capillary inhibition of hydrate growth.