Pore fabric assignment using electrical conductivity of some Albian-Cenomanian sequences in north Eastern Desert, Egypt

The electric pore fabric concept has been testified in many previous studies, mostly concerned with sandstone rock samples. The present study is a further trial to testify the reliability of the proposed concept on carbonate and clastic facies. The studied facies are representative for the Albian-Cenomanian Raha and Abu Qada Formations at the western side of the Gulf of Suez in Egypt. A total of 37 samples have been studied petrophysically by measuring electric conductivity in 3-D to rank their petrophysical potentiality and to detect their electric pore fabric. The studied samples are grouped into four facies, namely: (1) facies 1 (calcareous sandy siltstones) and (2) facies 4 (glauconitic quartz arenite) as clastic facies as well as (3) facies 2 (bioclastic limestones, and dolostones) and (4) facies 3 (clayey to sandy limestones) as carbonate facies. Porosity values of the studied carbonate facies are very good due to dolomitization and dissolution, whereas porosity values of the clastic facies are poor due to their high clay content. The formation resistivity factor values are low to medium values due to the reducing effect of the clay content and the very good porosity values. Archie's parameters a and m are mostly related to the formation resistivity factor and to some extent to the mineralogical composition as well as the electric tortuosity. The electric pore fabrics of the studied facies are slightly anisotropic, mostly as primary depositional fabrics affected by slight foliation rather than lineation. Presence of a slight fracturing system can be revealed by assigning the minimum formation resistivity factor through the vertical direction perpendicular to the bedding plain. However, the fracturing system is still not strong enough to affect the electric pore anisotropy by increasing the electric pore lineation as a secondary fabrics' indicator.