--> --> Palaeogeography and Palaeo-Earth Systems in the Modelling of Source Rock Depositional Space: The Predictive Mapping of New Oil and Gas Source Kitchens in the Atlantic Margin Basins of Morocco

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Palaeogeography and Palaeo-Earth Systems in the Modelling of Source Rock Depositional Space: The Predictive Mapping of New Oil and Gas Source Kitchens in the Atlantic Margin Basins of Morocco

Abstract

A key aspect of the exploration potential of the Atlantic Margin Basins of Morocco is the presence of mature source rocks. The emplacement, in the early Jurassic, of oceanic crust to form the juvenile Central Atlantic Ocean was accompanied by the formation of new marine basins that have the potential to host previously unrecognized source rocks. The distribution of source rocks and the lateral variation in source quality are some of the main uncertainties for exploration in frontier basins like these. To construct a predictive tool designed to address this problem, Plate Wizard reconstructions were used as the basis for global palaeogeographic mapping. Detailed palaeotectonics and palaeoenvironments maps were prepared. These base maps were compiled using a global database of palaeoenvironmental and lithofacies data, the legacy of over 30 years of petroleum geological studies and an equally extensive source rocks database. A novel method relating topography and bathymetry to plate tectonic environments was used in the construction of palaeo digital elevation models (DEMs). The DEMs were coupled with state-of-the-art palaeo-Earth systems models (U.K. Met Office HadCM3 palaeoclimate model) and an unstructured mesh model to simulate palaeotides (Imperial College, U.K., ICOM tide model). The database also includes climate proxies that were used to test the veracity of modelling results. In conjunction with the DEMs, palaeo-Earth systems were used to create a new predictive model of organic matter productivity, dilution and preservation. This model defines source facies depositional space for the selected time slices. The combined approach also provides an understanding of regional palaeogeographic and palaeoclimatic geohistory, drainage basin evolution, and the estimation of clastic sediment flux. Predictive mapping is used here to provide an assessment of source rock risk for the Toarcian (Early Jurassic), a key time slice in the development of the Atlantic Margin Basins of Morocco. The gridded model results provide an objective assessment of lateral variability in source quality that with burial and maturation models is the basis for mapping previously unrecognised oil and gas kitchens.