The role of reservoir compartmentalization in the failure of reservoirs of structurally complex accommodation zones: an example from The Morgan Accommodation Zone, Gulf of Suez, Egypt

Abstract

Compartmentalization of hydrocarbon reservoirs represents a global challenge in assessing and developing proven fields due to the necessity for a detailed survey of the field structures, burial history, and pressure system. The geological complexity arising from overlapping fault segments, kinematically linked fracture networks, and heterogeneous stratigraphic juxtapositions within accommodation zones between Gulf of Suez rift segments results in highly variable reservoir performance—yielding prolific hydrocarbon production in some fields, while others remain non-productive—and contribute to the occurrence of multiple oil-water contacts within individual producing reservoirs. We use structural restoration, basin modelling, pore pressure and fracture gradient modelling to assess the pre-rift reservoir failure and the variation of the oil-water contact in the syn-rift reservoirs of the Morgan accommodation Zone, Gulf of Suez. Our results show that: (1) pre-Miocene source rocks are too shallow for maturation due to complex fault linkages and interaction; (2) immature pre-Miocene source rocks prevent effective hydrocarbon generation and charge; (3) no overpressure above the Eocene Thebes Formation; lack of charge attributed to either immature source rocks at juxtaposition points or sealing faults; (4) a fill-to-spill mechanism governs Miocene syn-rift oil-water contact variations; deeper oil-water contact in western blocks results from better connectivity to mature source kitchens west of GS327. These results offer crucial new insights into the interplay of pressure regimes, migration routes, and reservoir compartmentalization governing hydrocarbon plays in complex accommodation zones.