If `compact sediments' is set as true (Compaction group file), the user can specify initial porosities of sand and shale as well as the decay constants.
The user can also specify whether or not erosion will have an effect on the compaction of sediments. If erosion affects compaction, the compaction is irreversible (i.e. it does not expand when the overburden is decreased). See Hart et al. (1995) for a discussion of this behavior.
We follow the approach of Sclater and Christie (1980) and assume porosity is an exponential function of depth:
fi is the percent sand (assuming only sand and shale are present), lshale is the parameter scaling the rate of compaction with depth (defined as `decay constant for shale compaction'), f0shale is the surface porosity of the shale (as defined by `initial porosity for shale'). Similarly, lsand is the parameter scaling of the rate of compaction of the sand with depth (defined as `decay constant for sand compaction') and f0sand is the surface porosity of the sand (defined as `initial porosity for sand').
We note that the default values from Sclater and Christie (1980) are:
If
Figure 12 Result of compaction (library file comp.dat with skip lines set to 39 and a vertical exaggeration of 75). Porosity has been contoured here with an increment of 0.02.
Last Modified: 01:21pm EST, December 12, 1995 - Steven E. Nelson
