Structural restoration and basin and petroleum systems modeling : case studies from the Monagas Fold and Thrust Belt, Venezuela and the Moroccan Atlantic Margin

摘要

This thesis proposes a workflow of integrating structural restoration and basin and petroleum systems modeling. It describes advantages and limitations, and its practical application in structurally complex geological environments dominated by tectonic compression and salt tectonics. The first part of the thesis (chapter 1) presents a study of the Monagas Fold and Thrust Belt onshore northern Venezuela and its deformed foreland basin. The chapter presents for the first time a two-dimensional structural restoration in combination with full PVT three-phase hydrocarbon migration modeling in the study area. The model contributes to the further understanding of the evolution of petroleum systems in fold and thrust belts in general and increases the knowledge of the study area in particular, as it explains the hydrocarbon charge of the main known fields and the relative absence of charge in other areas. In a more theoretical part, the study challenges the simple backstripping approach by applying the structural restoration technique for improved petroleum systems modeling. Particular attention is paid to the decompaction and compaction limitations and its implications for the modeling results. The second part of the thesis (chapters 2 and 3) addresses the offshore Essaouira salt basin and the outer Atlantic margin of Morocco. Chapter 2 focuses on the geodynamic and structural development of the study area. The work reveals for the first time the diachronic nature of geodynamic events related to the bypass of the Canary Island hotspot and the Atlas orogeny, and their influence on the folding of the deep-water margin and the salt tectonics. The chapter further proposes a conceptual model for the salt tectonic evolution through geologic time, explaining the regional variations as observed across the margin at present day. A salt restoration workflow, involving decoupled subsalt and salt-overburden restoration with salt-area balancing, and salt withdrawal and extrusion processes, was developed to improve the temporal resolution of salt tectonics and associated regional deformation. Chapter 3 applies for the first time structural restoration combined with petroleum systems modeling to the Moroccan Atlantic margin. The regional basin model, which reaches out to the western edge of the Moroccan Atlantic margin, contributes to the understanding of the thermal maturity of different potential source rock levels in this frontier exploration province. The integration of the structural restoration with petroleum systems modeling allowed to model hydrocarbon migration in the context of mobile salt, leaving behind an amalgamated basin stratigraphy after salt withdrawal and extrusion. Finally, the models have been used together with the regional observations and north-south variations to evaluate the prospectivity of speculative oil and gas plays and their likely changes along the yet little explored margin.