Upper part of Minnelusa Formation in outcrop near Beulah, Wyoming, and at West Mellott field, Powder River basin
The upper part of the Minnelusa Formation near Beulah, Wyoming, consists of dolomite, gypsum (anhydrite in the subsurface), and sandstone units that provide a three-dimensional sedimentologic and structural analog for upper Minnelusa oil fields such as West Mellott. Each dolomite records the initiation of marine transgression across relict topography of the previous cycle. Gypsum (anhydrite) above the dolomite records restriction of the water body as sea level began to fall. Low-energy marine, sabkha, and eolian-dune sandstones record continued regression. The extent and distribution of eolian dunes differ from cycle to cycle. Where eolian sandstones were not preserved, marine and sabkha sandstones are directly overlain by marine dolomites of the next cycle. At Beulah, gypsum onlaps and covers an eolian-dune complex tens of feet thick, forming a visual model of the reservoir-trap system at West Mellott field. Original intergranular pore space of the eolian-dune complex at West Mellott was about 40-45% and was probably pervasively filled with early gypsum (anhydrite) cement. Relatively late dissolution of anhydrite cement has preceded and overshadowed burial compaction, resulting in an increase of fluid-filled pore space (to as high as 30%) and a concurrent and somewhat incongruous decrease of intergranular pore space. At West Mellott, intergranular pore space is reduced from original levels but is still relatively high, and reservoir quality of sandstones is limited by incomplete anhydrite dissolution rather than by burial compaction.
- Research Organization:
- Geological Survey, Denver, CO (USA)
- OSTI ID:
- 6374045
- Report Number(s):
- CONF-8808223-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Vol. 72:7; ISSN AABUD
- Country of Publication:
- United States
- Language:
- English
Similar Records
Diagenesis of sandstones in Permian upper Minnelusa Formation, west Mellott field, Powder River basin, Wyoming
Sedimentology of Permian upper part of the Minnelusa Formation, eastern Powder River basin, Wyoming, and a comparison to the subsurface
Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
DOLOMITE
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC TRAPS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALS
MONTANA
NORTH AMERICA
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
POWDER RIVER BASIN
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
USA
WYOMING