Porosity, specific surface area and permeability relations in compacted sediments

Abstract EN

Theoretical relationships have been established among porosity, specific surface area and permeability of rhombohedrally-packed and well-sorted spherical grains under com- paction and pressure solution.

It is shown that during the compaction of such packed grains, the rate of loss of the specific surface area is initially fast, but is gradually followed by a slower rate of loss.

On the contrary, the rate loss of the grain volume itself gradually increases with the compaction of the grains.

On the basis of these gradual changes of both the specific surface area and grain volume and of Kozeny's theory, a porosity-permeability relationship of variable grain-size under pressure solution was developed.

If the grain material removed by the pres- sure solution is reprecipitated on the grain surfaces and/or al the grain-to-grain contacts, then both porosity and permeability will undergo further reduction.

A theoretical porosity-specific surface area-permeability relationship is presented with re- spect to a changing sorting factor.

Poor sorting of grains drastically reduces permeability values for a given value of porosity.

The theoretical relationships mentioned above may be useful in further understanding of the grain size, specific surface area and permeability aspects of actual reservoirs of granular type; a comparison can be made between the actual relationship with the theoretical one.