Reconstructing the Ocean Floor Shape in Turbidite Basins using Seismic Interpretations and Forward Modelling

Abstract

Deep-water depositional systems in different tectonic regimes display markedly different tectonostratigraphic evolution. The objective of this PhD was to develop a stratigraphic forward modelling program which deconvolves the controlling factors on basin fill architecture, in order to understand the dynamic interaction between structural deformation and sediment supply, using real, mapped structural geometries and stratigraphic package thicknesses. Understanding the interaction between structural deformation and sediment supply is important on active continental slopes. This interaction controls the vertical and lateral distribution of reservoir and seal lithologies, and their relation to growing structures. Subsurface prediction of trap and seal effectiveness is a vital component of CO2 sequestration or hydrocarbon exploration projects.
Onlapse-2D is a geometric-based stratigraphic forward modelling program that simulates the tectonostratigraphic evolution of mini-basins using only commonly available reflection seismic, age-dated horizon interpretations and well data, if available (not required). The resulting models efficiently simulate the stratal architecture and palaeobathymetry of the mini-basin through time. Onlapse-2D produces geologically realistic cross-sections of a range of idealized mini-basins and simulates the evolution of a mini-basin using real data in the Gulf of Mexico.
Through the modelling, I show that the development of offlap and onlap stratal terminations in structurally active mini-basins may be linked to sediment supply in some cases. However, in others the link between onlap and offlap may be weak or non-existent. Therefore, there is no requirement for the development of onlap or offlap to have a hard-wired link to extrinsic processes, such as relative sea-level change.
Simulating the tectonostratigraphic evolution of the Late Miocene within three mini-basins in the Sureste Basin of Mexico allowed me to test and develop the capacity of Onlapse-2D. This case study integrated high resolution age-dated horizons and well data with 3D-seismic horizon interpretations, and the model results revealed three phases of structural activity, which controlled the stratigraphic development in the Late Miocene. These comprise two distinct pulses of contraction-related folding, and the long-term effects of salt-withdrawal and diapirism. This case study highlights the capacity of Onlapse-2D to aid in hydrocarbon exploration, by predicting reservoir presence away from well control and by identifying candidate stratigraphic traps.

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