Figure 12: Madison limestone cluster analysis at the different threshold values: (A) 0.35, and (B) 0.55 that correspond to cluster valleys in Figure11.
The imaging and analysis processes previously described were also applied to fractured Indiana and Madison limestone samples, with the goal of observing both fracture and pore systems simultaneously. As previously seen in Figure 9 (non-fractured Indiana limestone), the cluster valley for this sample are observed at threshold values for the non-fractured Indiana limestone are 0.60, and 0.80. The fractured Indiana limestone sample shows similar characteristics to the non-fractured Indiana limestone of small and large vugs as shown in Figure 13. There is a new valley at the threshold 0.30, Figure 14A, because the sample is now more connected than before (the small pores and vugs are more accessible due to the fracture) and intense features in fractures and their vicinity exhibit less signal relaxation. This is exemplified by the threshold value of 0.60, which remains the same for both the fractured and non-fractured Indiana limestone samples, but the number of clusters reduces in the fractured Indiana Limestone (at threshold 0.60) changing from 6 cluster in Figure 10A to 2 clusters in Figure 14B. A cluster valley has also appeared at the threshold value of 0.70, suggesting that there is a new feature that has a proton density that is not a part of the small pore system or the vug system. This new proton density is assigned to the fracture that was manually created in the sample. Figure 14C clearly shows the fracture through the sample (green and gold feature). This fracture has made the vugs more accessible in the Indiana Limestone as shown in Figure 14D (threshold 0.80). There are more vugs present in the fractured sample when compared the non-fractured sample. This result is consistent with the fracture connecting the sample more so than before. Based on this analysis, the pore space in the sample has become more accessible to water, now that a fracture has been introduced. The pores, whether small or vug like, are more connected and therefore could allow better transport through the sample.