Hydrodynamic flow in lower cretaceous muddy sandstone, Gas Draw field, Powder River basin, Wyoming

Journal Article · Thu Oct 01 04:00:00 EDT 1981 · Mt. Geol.; (United States)

OSTI ID:5996606

Lin, J T.C.

Lower Cretaceous Muddy sandstones form a simple stratigraphic trap at Gas Draw field, northeast Power River Basin. The Muddy at Gas Draw can be subdivided into six zones. The lowest, sixth Muddy sandstone is fluvial in origin, and the overlying fifth sandstone is a transgressive marine deposit. The fourth zone represents a fluvial origin below to shallow marine above. The third zone is interpreted to be of fluvial-overbank origin with possibly a bay-lagoonal association. The second sandstone is suggested to be a deposit of a fluvial or deltaic environment. The first zone was deposited in a lagoonal and poorly-drained marsh environment. At Gas Draw, the second Muddy sandstone is the major producing zone and has the highest average porosity and permeability of 22.6% and 209 md. It had high initial production rates of up to 1200 BOPD (191 m/sup 3//day). From correlation of well logs, the Muddy reservoirs appear to be separated by thin shales, but analysis of drill stem tests show that these reservoirs are connected at some points within the area. Analysis of drill-stem test pressures provides the basis for interpreting fluid potential relationships. The average potentiometric gradient of 32 ft/mi across the field results in a hydrodynamic oil column of 210 feet, whereas capillary-pressure differences due to permeability changes can account for only 38 feet of oil column. The observed oil column over most of the field has a height somewhat greater than 250 feet which agrees well with total calculated oil column of about 248 feet. Furthermore, local decrease in permeability to oil may be responsible for water production at any place within the field, even updip from the producing area.

• Research Organization: Phillips Petroleum Co., Bartlesville, OK
• OSTI ID: 5996606
• Journal Information: Mt. Geol.; (United States), Journal Name: Mt. Geol.; (United States) Vol. 18:4; ISSN MOGEA
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
CRETACEOUS PERIOD
DRILL STEM TESTING
FLUID MECHANICS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC TRAPS
HYDRODYNAMICS
HYDROLOGY
MECHANICS
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NATURAL GAS FIELDS
NORTH AMERICA
PERMEABILITY
PETROLEUM DEPOSITS
POROSITY
RESOURCES
ROCKS
ROCKY MOUNTAIN REGION
SANDSTONES
SEDIMENTARY ROCKS
SHALES
TESTING
USA
WYOMING