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  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

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The ductility of a top seal can be estimated (1) by using laboratory data and log-derived density values that reflect the compaction state or (2) by comparing the strains in tested traps associated with successes and failures.

The [[Seal ductility|ductility of a top seal]] can be estimated (1) by using laboratory data and log-derived density values that reflect the compaction state or (2) by comparing the strains in tested traps associated with successes and failures.

==Shale ductility and density==

==Shale ductility and density==

[[file:evaluating-top-and-fault-seal_fig10-35.png|thumb|300px|{{figure number|1}}Ductility of shale. Data from Hoshino et al.<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|thumb|300px|{{figure number|1}}Ductility of shale. Data from Hoshino et al.<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>]]

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.