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S. Chereé Stover1
(1) University of Colorado, Boulder, CO

Abstract: The Effects of Salt Evolution, Structural Development, and Fault Propagation on Late Mesozoic/Cenozoic Oil Migration: A Two-dimensional Fluid Flow Study Along a Megaregional Profile in the Northern Gulf of Mexico Basin

Sequential two-dimensional forward modeling of fluid flow along a 600 kilometer megaregional cross-section across the northern Gulf of Mexico Basin illustrates the influence of structural, stratigraphic, and thermal evolution on oil generation and migration paths. Ten megaregional fluid flow models, spanning the Late Cretaceous to the Holocene, were constructed and interpreted. Model results indicate that salt evolution and excess pressure development strongly influenced Late Mesozoic/ Cenozoic oil migration patterns. Within the lower slope portion of the profile, early and fairly rapid maturation of source rocks was accompanied by slow elevation of excess pressures. Oil migration in this region was minimal and the impact of salt evolution on the fluid flow was limited. In the center of the profile, evolution of allochthonous salt and formation of high excess pressures, coeval with development of normal faults, significantly impacted oil migration patterns. Penetration of high excess pressure regimes by these faults directed fluid flow vertically upward. Upon encountering salt sheets, oil migration exhibited both divergent and convergent flow patterns, with oil flowing laterally along the base of the salt. Evacuation of allochthonous salt in the central and northern regions of the profile caused lateral migration patterns. However, when excess pressures in these regions exceeded 50 MPa, vertical oil flow through the salt welds and along suprasalt faults occurred. A localized and well-constrained study of oil migration in the Oligocene-Miocene detachment province further suggests that faults play important roles as migration pathways, with episodic flow directing oil migration into shallow reservoirs.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana