Changes

==Shale ductility and density==

==Shale ductility and density==

The ductility of a shale top seal is a function of compaction state. Uncompacted, low-density shales are extremely ductile and can thus accommodate large amounts of strain without undergoing brittle failure and loss of top seal integrity. Highly compacted, dense shales are extremely brittle and undergo brittle failure and loss of top seal integrity with very small amounts of strain.

The ductility of a shale top seal is a function of compaction state. Uncompacted, low-density shales are extremely ductile and can thus accommodate large amounts of strain without undergoing brittle failure and loss of top seal integrity. Highly compacted, dense shales are extremely brittle and undergo brittle failure and loss of top seal integrity with very small amounts of strain.

The following figure shows the relationship between ductility and density for 68 shales. The ductility of the shales was measured in the laboratory at confining pressures of 1, 200, and 500 kg/cm². All samples were deformed in compression.

The following figure shows the relationship between ductility and density for 68 shales. The ductility of the shales was measured in the laboratory at confining pressures of 1, 200, and 500 kg/cm². All samples were deformed in compression.

[[file:evaluating-top-and-fault-seal_fig10-35.png|thumb|{{figure number|10-35}}Data from .<ref name=ch10r37>Hoshino, K., Koide, H., Inami, K., Iwamura, S., Mitsui, S., 1972, Mechanical properties of Japanese Tertiary sedimentary rocks under high confining pressures: Geological Survey of Japan Report 244, 200 p.</ref>]]

[[:file:evaluating-top-and-fault-seal_fig10-35.png|Figure 1]] illustrates the following:

 

Figure 10-35 illustrates the following:

* Shales with a density less than approximately 2.1 g/cm³ deform ductilely and not by brittle failure at the range of confining pressures found in most sedimentary basins.

* Shales with a density less than approximately 2.1 g/cm³ deform ductilely and not by brittle failure at the range of confining pressures found in most sedimentary basins.