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Previous HitFaultNext Hit Geometry Control from Fluid Migration and Localisation of Diagenesis Around the Moab Previous HitFaultNext Hit, Utah

Stuart D. Burley1, Stuart M. Clarke2, and Ross I. Garden3
1BG Trinidad, c/o BG Group, Reading, United Kingdom
2Basin Dynamics Research Group, Department of Earth Sciences, University of Keele, United Kingdom
3BG Oman, c/o BG Group, Reading, United Kingdom

The Moab Previous HitFaultNext Hit, a NW-trending, normal Previous HitfaultNext Hit with ca 960m maximum surface throw outcrops for ≥ 45km within the NE part of the Paradox Basin, Utah, U.S.A. The Previous HitfaultNext Hit displaces a sedimentary sequence of Pennsylvanian to Cretaceous age. Outcrop mapping indicates that diagenetic cementation occurred in the ca 50m wide deformation zone around the Previous HitfaultNext Hit but was concentrated in high strain areas, such as bends and branch points along the Previous HitfaultNext Hit. Volumetrically, the most significant authigenic minerals are ankerite and calcite, which show increased abundance proximal to the Previous HitfaultNext Hit and extend up to 200m from the Previous HitfaultNext Hit at branchpoints. Reduction of iron oxide and cementation with pyrite is also concentrated at the same high strain locations but extends up to 7km from the Previous HitfaultNext Hit and is best developed at structural highs and in high permeability Jurassic sandstones below capping mudstones.

A combination of structural and fluid flow modelling, with spatial analysis of diagenetic mineral distribution indicates that large scale fluid flow along the Moab Previous HitFaultNext Hit is concentrated at structurally complex sites. Away from these sites, there is only minor fluid migration along the Moab Previous HitFaultNext Hit. Diagenesis is attributed to ingress of hydrocarbon and aqueous fluids into high permeability sandstones. Previous HitFaultNext Hit-related fluid flow occurred during a relatively short lived episode of Previous HitfaultNext Hit valving. Three-dimensional structural modelling indicates that up-dip hydrocarbon migration from hanging-wall kitchens was focused towards cross-Previous HitfaultNext Hit migration pathways at branch points and subsequent migration within the footwall was directed towards the footwall high, sealed by a well-developed clay gouge rich Previous HitfaultTop zone. Hydrocarbon migration was driven by overpressure generation which resulted from gas generation within Paradox Formation traps.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas