Diagenesis and petrophysical characteristics of the shallow Pliocene sandstone reservoirs in the Shinfas Gas Field, onshore Nile Delta, Egypt

Abstract

The Pliocene Kafr El-Sheikh (KES) Formation in the onshore Nile Delta region hosts numerous shallow gas accumulations. These are readily detected on seismic profiles by definable direct hydrocarbon indicators (DHI). However, the presence of residual gases causes many production failures. Two shallow (< 1500 m) pay zones were investigated in this study; both display seismic flat bright spots. The shallower pay zone (pay zone 1) comprises prograding distributary channel-fill sandstones, whereas the deeper pay zone 2 constitutes the transgressive distal sand bars. Pay zone 1 sandstones have better reservoir quality in terms of porosity (Av. 25.68%), permeability (86 md), water saturation (Av. 43.26%), and hence host thick gas accumulation (~ 15 m) with high net/gross (N/G) ratio ~ 0.98. On the other hand, pay zone 2 has a significant reservoir heterogeneity and contains only residual gases with N/G ratio of 0.26. The eodiagenetic infiltration of clays (Av. 31.46%), authigenic precipitation of glauconite (Av. 7%), and formation of pseudomatrix materials (Av. 2%) in pay zone 2 sandstones have the most detrimental impact on their reservoir quality. Elevated water saturation in pay zone 2 (Av. 64%) reduced the movable hydrocarbon content and results in accumulation of residual gases. Mild mechanical compaction preserved the intergranular porosity of the pay zone 1 sandstones, and incursion of meteoric water facilitated the dissolution of feldspars, the neoformation of secondary pore spaces (Av. 2.9%), and thus increased the reservoir storage and flow capacities. This study highlights that the initial depositional setting of the shallow siliciclastic reservoirs controls their diagenetic pathways and hence their reservoir quality.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Gas-generative potential for the post-Messinian megasequence of Nile Delta Basin: a case study of Tao Field, North Sinai Concession, Egypt

“…Loncke et al 2002;Zachos et al 2001). Throughout this phase, the deltaic sedimentation process prevailed in deep-water part as turbidities with well-developed slope channels and distal ical data with interpretation for zone J represents the highly promising characteristics for gas production for zone J fans (Dolson et al 2005;Leila and Mohamed 2020). The shape of the Nile Delta is asymmetric as it is characterized by steep eastern side due to very rapid sedimentation of the Plio-Pleistocene sediments.…”

“…The shape of the Nile Delta is asymmetric as it is characterized by steep eastern side due to very rapid sedimentation of the Plio-Pleistocene sediments. However, the western side is gentler and more dominated by extensive slope channel systems (Dolson et al 2005;Leila and Mohamed 2020) as displayed in Fig. 21.…”

“…Moreover, studying the reservoir facies and diagenetic pathways is vital for expecting the distribution of different diagenetic characteristics which strongly control the quality and reduce the exploration risks for these shallow Pliocene gas reservoirs in the Nile Delta (Leila and Mohamed 2020).…”

“…The sands of the Early-Middle Pliocene (Kafr El-Sheikh Formation) in addition to the Late Pliocene (El-Wastani Formation) characterize the most optimistic targets for gas exploration within the offshore portions of the Nile Delta (e.g. Lashin and Mogren 2012;Othman, et al 2018;Abd El-Gawad et al 2019;Leila and Mohamed 2020;Elatrash et al 2021). This is because the Pliocene sequence in Nile Delta Basin does not include challenges in exploring new plays.…”

The potential of offshore Nile Delta Basin natural gas reserves: a case study of Messinian reservoir in Baltim field

“…(Early-Middle Pliocene) as well as the El-Wastani Fm. (Late Pliocene) are the most promising opportunities for gas exploration in the Nile Delta's offshore areas (e.g., Othman et al 2018;Lashin and Mogren 2012;Leila and Mohamed 2020). In general, there are no difficulties in exploring new plays in the Pliocene section of the NDB.…”