Petrophysical Evaluation Of Shaly Sand Reservoirs in Sequoia Field,Nile Delta,Egypt

Abstract

The present work is devoted to the study of general geological setting and structure setup in Sequoia field , north western margin of the Nile Delta west delta deep marine concession (WDDM). The study includes calculation of petrophysical parameters(porosity –permeability- formation water resistivity –hydrocarbon and water saturation-shale content)for Sequoia reservoirs rocks using advanced logging tools (Combinable Magnetic Resonance tool “CMR”) and conventional logging tools(Gamma ray-Density-Neutron –Resistivity) in nine wells ,and aiming to define litholosaturation Crossplots and the lithologic identification Crossplots, the lateral variation of the lithology and the different saturation distribution in the Pliocene reservoir and comparison of the different saturation models(Dual water and Indonesian ) to select the best one for this reservoir has been made. The study established the hydrocarbon potentialities of the sequoia reservoir (Фt, Vsh, Фe, Sw, Sh) using IP software . Study of the lithology and clay mineralogy of this reservoir in all wells of the study area through Thorium ,photo electric effect, potassium and neutron densityCrossplotswas done. A detailed petrophysical evaluation through lithosaturation crossplots using advanced logging tools (CMR) and conventional tools is presented. Study of the lateral connectivity of the reservoirs through a number of percentage maps of petrophysical parameters like total and effective porosities,permeability andwater saturation from CMR tool and Conventional tools was done as well. MDT pressure data was taken for 7 wells to several compartments in the Sequoia field tostudy the vertical connectivityof the reservoirs. The results showed that average effective porosity calculated from Neutron –Density ranges from18% to 32%, while average effective porosity calculated from CMR using DMR method ranges from 18 % to 31%. The average water saturation calculated from conventional tools (Dual water and Indonesian) ranges from 38% to 68%, while theaverage water saturation calculated from CMR ranges from 39 % to 77%The average calculated permeability from CMR using Timur – Coates model ranges from 30 to 890 md on the other hand the results show that the water saturation from Dual water model is the closest model to the water saturation calculated from CMR, and this variation is due to conventional tools are fluids and lithology dependent while CMR is only fluids dependent, and the study recommended to drill new wells and increase depth of drilled wells Sequoia D5 and Sequoia D6to develop this field. .