Darrell W. Sims1, David A. Ferrill1, Alan P. Morris2, Michael Ferguson1, Rasoul Sorkhabi3
(1) CNWRA, Southwest Research Institute, San Antonio, TX
(2) Division of Earth and Physical Sciences, University of Texas at San Antonio, San Antonio, TX
(3) Japan National Oil Corporation, Chiba, Japan
ABSTRACT: Influence of Fault Geometry on Reservoir Connectivity
Sandbox analog modeling experiments provide new insights into the effects of structural geometry on reservoir connectivity. Progressive deformation of the models indicates that the potential for hydrocarbon trapping and compartmentalization increases and that the potential for reservoir communication decreases as fault systems mature. For example, experiments of distributed extension (deformation over a rubber sheet) demonstrate that geometrically simple faults nucleate at a large number of sites throughout the deforming region. Initially, relay ramps and forced folds over blind faults form potential hydrocarbon pathways. As deformation proceeds, structural relief increases and potential reservoir communication pathways are severed as faults merge by lateral and upward propagation or ramp breaching. This structural evolution progressively creates more opportunities for trapping and compartmentalization, and results in decreased reaservoir connectivity. The experiments demonstrate that this geometric evolution occurs at many scales. Large-displacement faults show clear, large-scale examples of the geometric maturation of potential hydrocarbon communication pathways (e.g., relay structures) into potential hydrocarbon traps (e.g., breached relay ramps or faults merged by lateral propagation). In the models, these same processes also occur within the deformed region at smaller scales. Analog models of contractional and strike-slip deformation exhibit similar relationships between degree of structural development and reservoir connectivity.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado