Low Resistivity Pay in Offshore Nile Delta: Quantification using Multicomponent Induction Logging

By

 Mette Munkholm¹, Dr. Mohamed Nashaat², Dr. Andy Samuel³, Edward Webb², Cormac Parsons¹, Patrick Hogarty⁴

(1) Baker Atlas Geoscience, Milan, Italy (2) RASHPETCO, Cairo, Egypt (3) BG Group, Reading, England (4) Baker Atlas Geoscience, Cairo, Egypt

Accurate quantification of low resistivity pay is a challenge within the gas reservoirs discovered in the WDDM Concession. Until recently NMR and image logs have served as the primary logs to evaluate the laminated sections. NMR logs can improve the estimate of hydrocarbon storage capacity and image data can improve the quantification of net sand, saturations in the sand laminae are difficult to quantify. In wells drilled near perpendicular to bedding conventional resistivity instruments measure the resistivity along bedding, the horizontal resistivity, this measurement is dominated by shale conductivity, which makes it difficult to quantify saturations of the sand laminae in low resistivity pay sections. A measurement of the resistivity perpendicular to bedding, vertical resistivity, is more sensitive to resistive, hydrocarbon bearing sand laminae. This type of measurement was previously unavailable. Horizontal and vertical resistivities have been obtained with the 3D Explorer^SM Multicomponent Induction Logging Instrument (3DEX^SM) in a well on a WDDM discovery. These data, in combination with standard open hole log data, are used in a robust petrophysical model utilizing macroscopic electrical anisotropy to determine both laminar shale volume and laminar sand resistivity. When integrated with the conventional Thomas-Stieber porosity model a significant improvement in hydrocarbon saturation is obtained. The tensor resistivity petrophysical results are confirmed against pay observations from core and image data. Bulk volume hydrocarbon meters computed from 3DEX data show an increase from 27% up to 179% over several intervals of this well.