Abstract: Porosity Loss in Sandstone by Ductile Grain Deformation During Compaction

E. F. McBride

As exploration moves to greater depths, attention must be paid to the amount of porosity lost in sandstones by compaction. Deformation of ductile grains is the chief cause of porosity reduction during compaction, except in nearly pure quartz sandstones. Shale clasts and micaceous rock fragments (slate, schist, phyllite, etc) are the chief ductile grains in sandstone, but glauconite and other fecal pellets are locally abundant. The amount of porosity loss by deformation of these grains depends on their abundance and the amount of overburden. It is common for sandstones to lose from 5 to 15% of their original total porosity this way, and some lithic arenites have lost their entire porosity during compaction. Knowledge of sandstone composition is helpful in predicting the am unt of porosity lost by ductile grain deformation.

AAPG Search and Discovery Article #90965©1978 GCAGS and GC Section SEPM, New Orleans, Louisiana