Porosity-Permeability Relationships in the Early Oligocene Algal Limestone Member of Wadi Al Buwayrat, Tansolukh Area, Al Jabal Al Akhdar, NE Libya

This paper reports a series of ten (10) porosity -permeability analyses and supporting petro graphic and sedimentologic descriptions from the Early Oligocene (Al Bayda Formation) of Algal Limestone Member strata sampled from an escarpment in Wadi Al Buwyrat, Tansolukh Village, Al Jabal Al Akhdar.The samples analyzed are not only mainly coarse bioclastic limestone from platform -top facies, but also include some micritic or lime-mud rock plugs from deeper water slope to basinal facies.Outstanding characteristics of this data set are the wide ranges of porosity (total; Ø t and macro; Ø m ) and permeability (K) in all studied limestone samples and the large degree of short -range heterogeneity typical of these strata, and the better total porosity -macro-porosity correlation of the studied Algal Limestone .The Algal limestone samples as revealed by petrographic examination , have experienced widely varying calcite cementation, some clay-rich (micritic) limestone and dissolution through some vuggy porosity and localized moldic porosity which may show clear evidence of meteoric diagenesis, suggesting that sub-aerial exposure may have played an important role in porosity-permeability evolution.Permeability for -given -porosity is controlled by grain size calcite cement and provided vuggy porosity, and by the occurrence of some unconnected moldic porosity in mud-rich samples.As a result, there is no correlation in porosity-between total (Ø t ) and macro porosity (Ø m ) and their equivalent permeabilites (K).This trendless relationship may be interpreted as reflecting an overall lower permeability for a given porosity that led to more muddy depositional facies greater cementation and lesser grain dissolution and connectivity.