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AAPG Annual Convention and Exhibition

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Upscaling Previous HitFaultNext Hit Flow Properties for Evaluation of Cross-Previous HitFaultNext Hit Flow

Abstract

An ongoing concern in flow modeling across faults is upscaling the Previous HitfaultNext Hit-rock flow properties measured in the lab on cm-scale to the meter and tens of meter scale suitable for evaluating within-reservoir flow and exploration-scale sealing. It is proposed that upscaling is best accomplished by stochastic modeling of cross-Previous HitfaultNext Hit flow guided by the geometries of Previous HitfaultNext Hit-generated rock bodies (“geobodies”) as observed on outcrop. Preliminary models demonstrate that most resistance to flow transverse to the Previous HitfaultNext Hit is in the low permeability Previous HitfaultNext Hit rocks the Previous HitfaultNext Hit core as opposed to the damage zone of deformation in the Previous HitfaultNext Hit zone. Published and proprietary outcrop studies have demonstrated that the Previous HitfaultNext Hit core is heterogeneous normal to the Previous HitfaultNext Hit. Spatial correlation of lithology transverse to the Previous HitfaultNext Hit core is on the order of mm to a cm, much too small to improve estimates of upscaled flow properties. Length of constituent bodies in the Previous HitfaultNext Hit core can be traced along the Previous HitfaultNext Hit on the scale of cm to meters in different settings. The Previous HitfaultNext Hit core is best described as a composite of plate-shaped or equant geobodies with different permeabilities and seal capacities. Upscaling by numerical simulations of flow in composite rocks with these geometries can be compared to mathematical upscaling averages. Equant geobodies result in upscaled permeabilities very close to the geometric mean of the constituent geobody permeabilities and their volumes. Sealing depends on the relative size of the geobody relative to the width of the Previous HitfaultNext Hit core. Plate-shaped geobody constituents lead to upscaled permeability between the harmonic and geometric means of the constituent geobody permeabilities, with upscale permeability approaching the geometric mean as the shape of the constituent geobody approaches equant. The thinner the geobody relative to the Previous HitfaultNext Hit core width, the greater the seal capacity of the composite medium. Realistic upscaling of lab-measured permeability to real faults therefore depends on both the fractions of geobodies with different interpreted permeability and the likely geometry of the geobodies. Settings with smear and shearing of ductile rocks lead towards platy Previous HitfaultNext Hit core geometries, whereas settings where lenses or protolith is mixed into the Previous HitfaultTop core lead towards a more equant geobody shape.