International Journal of Petroleum and Petrochemical Engineering (IJPPE) Volume 3, Issue 1, 2017, PP 7-21 ISSN 2454-7980 (Online) DOI: http://dx.doi.org/10.20431/2454-7980.0301002 www.arcjournals.org ©ARC Page | 7 Porosity-Permeability Relationships in the Early Oligocene Algal Limestone Member of Wadi Al Buwayrat, Tansolukh Area, Al Jabal Al Akhdar, NE Libya Omar B. Elfigih, Ebrahim A. Al-Orabi Department of Earth Sciences, Faculty of Science University of Benghazi, Benghazi-Libya Abstract: 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. Keywords: Graphic representation; Total porosity; Macro porosity; Permeability; Algal Limestone; Tansolukh area. 1. INTRODUCTION The area of investigation is a part of Wadi Al Buwayrat, Tansolukh region, represented by stepped high escarpment composed mainly of a thick bedded Alga Limestone Figure 1. This paper summarizes porosity – permeability data from ten elevation points (155m to 177m) where good exposure of Algal Limestone rocks is characterizing one of the highest escarpment at Wadi Al Buwayrat Figure 1. Also it describes the sample materials and their lithologic and stratigraphic context, discusses probable controlling factors on porosity- permeability data, and how total porosity (rock plug porosity; Ø t ) and macroporosity (thin section porosity; Ø m ) may affect permeability (K) of the investigated rock unit. Together with observation about sedimentology , stratigraphy and petrography, these data provide a comprehensive characterization of the petrophysical parameters (porosity "Ø" and permeability " K") of the Algal Limestone units in the study area . Published information on the permeability-porosity relationship and trends of micro porosity/total plug porosity versus permeability is sparse, but general reviews are given in Saller and Henderson (1998) [1], Ehrenberg (2004a) [2], Ehrenberg et al. (2004b) [3], Ehrenberg et al. (2006) [4], Baker et al. (2013) [5], AlRatrout et al. (2014) [6] and Rahmouni et al. (2014) [7].