AAPG Middle East Region Geoscience Technology Workshop, Rift Basin Evolution and Exploration

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Coupling Basin Modeling and Lithospheric Modeling for Exploring Rift Basins

Abstract

Hydrocarbon-rich rift basins present a wide variety of structures and histories. Some are very young such as the Red Sea, others are very old and still productive such as the Barents Sea. Some have experienced a passive margin history after the rifting phase such as the Brazilian Pre-Salt basins, others have remained intra-continental rift basins with sometimes a complex polyphasic rifting history such as the Sudanese rift systems. Common points between all these rift basins are the high heat flow during the rifting phase(s) and the high sedimentation rates first related to focalized tectonic activity and then to widespread thermal subsidence. Although sedimentary patterns are extremely variable in rift basins, thick and localized lacustrine source rock as well as evaporites units sealing the system are widely found. In this context, petroleum system analysis requires a sophisticated modeling of the thermal history as well as a detailed prognosis of the sedimentary compaction and of the pressure field. This presentation will show different modeling examples of such basins through the world. For instance, coupling lithospheric evolution with sedimentation and integrated petroleum system modeling has proven to add value compared with user-defined heat flows applied at the base of sediments. It will be shown that the blanketing effect due to high sedimentation rate or salt diapir formation has a transient impact on the heat flow history in the lithosphere deep below the basement/sediment interface. Classic approaches based on uniform stretching factors will also be discussed as they are limited in the case of hyperextended margins where more complex models are required. In this regard, an improved lithospheric model allowing a precise description of the lithosphere shape and properties through time will be introduced. These modeling examples demonstrate the strength of the approach to build reliable geological reconstruction of the heat flow and of the pressure field through time, even from a minimum of data and in a limited time, which eventually leaves room for sensitivity and risk analysis.