Innovative Non-Conductive Mud Borehole Imaging Technology Improves Turbidite Reservoir Characterization; Offshore Nile Delta, Egypt

Emam, M. (Schlumberger) | El Araby, A. (Schlumberger) | Nassar, M. (Schlumberger) | Felifel, E. (Schlumberger)

OnePetro 

Abstract

The Eastern Mediterranean hosts some of the largest and most prolific gas reservoirs in the region. These reservoirs have been deposited as slope submarine channels and basin floor turbidite sand sheets. The quantity and quality of production is often controlled by the architectural elements encountered. Slumped and deformed facies could hinder production in submarine channels of the slope setting, which are limited in lateral extent. Although laterally continuous and parallel thinly bedded turbidite sheets of the basin floor offer great lateral extent, they often exhibit poor vertical connectivity and low apparent resistivity due to thinly bedded sand/shale sequences.

An exploratory well was drilled in the Offshore Nile Delta targeting slope and basin floor deposits. Although seismic attribute interpretation provided a general outline of the area, there remained the uncertainty of whether the depositional setting encountered by the penetrated succession belonged to slope channels or basin floor setting. The value added through borehole image integration provided information regarding some unanswered questions: 1) Are sidewall cores representative of surrounding lithology? 2) Do sedimentary features support a slope or basin floor model? 3) Are there natural fractures to enhance porosity? 4) What is the reason for low porosity in the sands? 5) Are there additional thin beds between channel elements?

To answer all these questions, detailed structural, sedimentological and sand count analyses were performed on the micro-resistivity image, logged over a 500 m succession. Interpreted electro-facies differentiated the internal architectural elements from structural events within the penetrated succession. Slumping and water escape structures supported a slope channel setting while dip patterns directly above channel fills were interpreted as levee complexes of nearby channels. Sand counting of the image resistivity arrays included all possible thin beds that could contribute to pay while excluding all deformed facies that would hinder production performance.