Evaluation of the Late Messinian Abu Madi sandstone reservoirs in the West Al Khilala gas field, Onshore Nile Delta, Egypt

Abstract

In this study, we integrated cores and wireline logs to evaluate the petrographical and petrophysical properties of the Late Miocene Abu Madi sandstone reservoir from the onshore WAK gas field. Thin section petrographic analyses indicate that the reservoir consists of coarse to fine-grained, poorly sorted, subangular to subrounded glauconitic quartz arenites exhibiting high mineralogical maturity, poor textural maturity, and good volume of intergranular porosity. Based on the downhole pressure data, we estimated that the gas gradient was somewhere between 0.24 and 0.26 psi/m. The SEM images suggest the pore filling authigenic chlorite and kaolinite cementation to be the dominant diagenetic process reducing the reservoir quality. The presence of concavo-convex grain contacts in the reservoir samples is indicative of a moderate degree of mechanical compaction by burial load. The massive sandstone reservoir facies represents stacked braided fluvial channels deposited during a lowstand system tract unconformably above the Qawasim Formation. Based on well log-based petrophysical analyses, the Abu Madi reservoir has a total porosity of 17–20 % with 14.6–18.3 % effective porosity and 39.4 to 47.9 % water saturation. Gross reservoir thickness varies between 28.3 and 51.1 m, whilst the net pay thickness ranges between 18.4 and 43.7 m, which translates to a high net-to-gross (N/G) ratio of 0.65–0.84. Lateral distribution of the petrophysical parameters infers a superior reservoir quality towards the central part of the studied field which should be targeted for future infill development well drilling. The reservoir heterogeneity was mapped to substantially decrease the uncertainty of future drilling.