--> Abstract: Structural Compartmentalization and Reservoir Fluid Distribution in the Terry and Muddy (J) Sandstones, Denver Basin, Colorado, by R. M. Slatt, and R. J. Weimer; #90946 (1997).
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Abstract: Structural Compartmentalization and Reservoir Fluid Distribution in the Terry and Muddy (J) Sandstones, Denver Basin, Colorado

SLATT, ROGER M., and ROBERT J. WEIMER

Five Previous HitbasementNext Hit wrench Previous HitfaultNext Hit systems have been mapped on top of the Muddy (J) Sandstone in the central Denver basin. Major faults are 10-15 miles apart, but the intervening areas are cut by numerous synthetic and antithetic faults. In a nine township area (including Denver International Airport), 10-90 ft thick Muddy (J) Sandstone reservoirs are compartmentalized owing, at least in part, to one of these structural trends. Near-vertical faults which form compartment boundaries trend both northeast and north-northwest and have offsets of 10-90 ft. Evidence for compartments includes gas opposite oil at the same structural elevation across faults, and gas downdip from oil. Faulting and associated fracturing may enhance production or provide seals by silica diagenesis, gouge, and/or juxtaposition of sandstone against shale.

Similar Previous HitfaultNext Hit Previous HitpatternsNext Hit divide the Upper Cretaceous Terry Sandstone into a number of Previous HitfaultNext Hit Previous HitblocksNext Hit of variable size in the sandstone trends of the Latham Bar/Hambert/Aristocrat fields. Vertical offset is on the order of 10s of ft. Evidence which suggests faults are sealing include: (a) higher normalized GORs for structurally higher wells within small single Previous HitfaultNext Hit Previous HitblocksNext Hit and/or for wells in upthrown Previous HitblocksNext Hit than for wells in downthrown Previous HitblocksNext Hit, (b) gas-oil contacts at different elevations across Previous HitblocksNext Hit, (c) log bulk densities which are higher in wells cut by faults (suggesting a relatively high-density cement-fill), and (d) one core which exhibits calcite-filled fractures/faults.

Since numerous faults are now known to penetrate the entire Cretaceous section in the Denver basin, the sealing Previous HitfaultNext Hit Previous HitblockTop compartment model presented here should be applicable to other Cretaceous reservoir intervals in this, and perhaps other, Rocky Mountain basins.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado