Normal and abnormal porosity-depth relationship of tertiary rocks in Soluq depression, NE-Libya.

Abstract

The principle aim in this analysis is to evaluate and interpret the porosity-depth relationships in theTertiary rocks in the Soluq Depression. Generally, the porosity in a formation is a function of its presentdepth only when that depth is its maximum depth of burial. From sonic log interval transit-time for tenwells scattered in the area, the porosity has been estimated, in order to evaluate and analyse the historyof burial and erosion in the sedimentary sequences deposited on the western margin of the SoluqDepression. The comparison of modelled normal compaction trends with actual compaction trends canbe used to quantify zones of over-compaction and under-compaction in a rock column. The porosityanalysis in this research is basically based on the comparison of the observed shale and limestoneregression lines with the normal porosity-depth model. The normal porosity-depth model representsmeasurements on ‘pure’ shales and limestones, which are believed to be at their maximum depth ofburial. The difference between the two curves may allow any depth of burial anomalies to be identifiedthrough the rock columns in the Soluq Depression.