Source rock evaluation of subsurface Devonian-Carboniferous succession based on palyno-organic facies analysis in Faghur Basin, North Western Desert of Egypt: a division of the North Africa Paleozoic Basins

摘要

The Paleozoic rocks in North Africa are prolific with source rocks that contribute petroleum to giant fields especially in Algeria and Libya. The coeval subsurface source rocks from the Devonian and Carboniferous in the Western Desert of Egypt have been evaluated in the present study. The rocks from Zeitoun, Desouqy, and Dhiffah formations have been evaluated based on integration of the palynofacies, organic geochemical analysis, and well logging. The study depends on samples from five wells that are Buchis-1X, Phiops-1X, Siwa-D-1X, Tayim West-1X, and WKAL C-1XST. The distribution of palynofacies categories are statistically investigated by the principal component analysis (PCA) that specified the proximal-distal environmental trends by the values of component 1 that attributed to the terrestrial organic sources. The analyses revealed mostly poor, fair to good organic enrichments and poor to fair source potential in the studied rocks. The samples are mostly thermally mature, uncontaminated, and of gas prone type III and mixed oil/gas prone type II/III kerogen. The geological conditions that lead to the large difference in the hydrocarbon source potentiality between western North Africa and source rocks evaluated in this study from Egypt have been discussed. It is suggested that these differences resulted from the larger thickness of Paleozoic rocks and the increase in burial depths of the depocenters in the western side that lead to higher maturity levels that are responsible for the organic conversions and hydrocarbon expulsion.