Petroleum Systems of the Western Nile Delta: Lessons Learned from an Integrated Organic Geochemical and Basin Modelling Approach

Vandré, Claudius¹, Bernhard Cramer², Peter Gerling², Axel Kellner³, Jutta Winsemann⁴ (1) Hydro Oil & Energy, Research Centre Bergen, Bergen, Norway (2) BGR - Federal Institute for Geosciences and Natural Resources, Hannover, Germany (3) RWE Dea Egypt, Cairo, Egypt (4) Institute of Geology, Leibniz University of Hannover, Hannover, Germany

Over the last decade the Nile delta of Egypt has emerged as an important gas province, as development of fields has significantly increased Egypt's annual gas production. Intensive exploration efforts applying state-of-the-art techniques led to many new commercial gas discoveries especially in deep waters. Production to date has been in the basin from Neogene sandstones in water depth up to 500 m. Good knowledge about the petroleum system is a prerequisite for reducing risk by drilling of deeper pre-Miocene prospects and within the deep and ultra deep water of the Nile delta. A regional geochemical study coupled with 2D petroleum systems modelling was applied to identify gas origins, define hydrocarbon kitchens and migration pathways and their evolution through geologic time. Chemical and isotopic characteristics of test gases indicate variable gas mixtures of both microbial and thermogenic origin. The natural gases are frequently accompanied by condensates (41-56 °API). Microbial gas contributions in shallow Plio-Pleistocene plays range from 30 to 95 %, but are around 10 % in older Miocene reservoirs. Accordingly, headspace gases show an overall increasing trend in gas wetness with depth. We inferred the existence of mainly gas-prone source rocks within the Middle Jurassic, Lower and Upper Cretaceous, Oligocene, and Lower Miocene. However geochemical gas-source maturity estimations compared to modelled timing of thermal maturation narrowed down the probability of effective source rocks within the Lower Cretaceous to Oligocene stratigraphic section. 2-D basin modelling suggests that the onset of hydrocarbon generation and expulsion is governed by deposition of the thick Miocene to Pleistocene overburden and is still an ongoing process. Petroleum migration would have occurred principally up-dip along normal faults and through unconsolidated sediments.