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Shale 3D flow and interaction with basement faultsin the Niger Delta deep-water fold and thrust belt
  • Vincenzo Spina,
  • Stefano Mazzoli
Vincenzo Spina
Total Upstream Nigeria Ltd.

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Stefano Mazzoli
University of Camerino
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This study is based on a large 3D seismic dataset in the deep-water domain in the Niger Delta. The study area is characterized by a series of WNW-ESE trending anticlines cored by shales. They developed by shortening at the toe of the gravity system since Miocene times. Four units of syn-kinematic sediments, reaching a maximum thickness of ~ 800 m, accumulated in the tectonically subsiding synclines during fold amplification between ~ 9.5 Ma and ~ 1.8 Ma. The volumes of syn-kinematic units roughly balance those of the shales accumulated in thickened fold cores. This feature is consistent with folding resulting from buckling controlled by the competence contrast between isopach Cenozoic units and underlying overpressured shales of the Akata Formation. This interpretation rules out the occurrence multiple thrust flats, the maximum cumulative shortening associated with folds and related thrust ramps being of ~ 3.5 km.
A dense network of NE-SW striking oblique extensional faults offsets a prominent anticline characterized by a NE-SW trend (which is almost perpendicular to the regional fold trend). These faults form a narrow, continuous deformation zone extending for tens of kilometers along and beyond the length of the anticline. The faults, rooting within the shales of the Akata Formation, formed since ~ 5 Ma and deform the seabed. Displacement distribution suggests mechanical interaction between isolated fault segments within the deformation zone. The latter is interpreted as the shallow expression of a deep-seated fault zone inherited from the segmented passive margin and marked by gravity and magnetic data.
09 Jun 2023Submitted to ESS Open Archive
11 Jun 2023Published in ESS Open Archive