Judith River Formation beneath Fort Peck Indian Reservation - proven high plains gas frontier in northeastern Montana
As one of the progradational sequences in the Late Cretaceous, the Claggett-Judith River cycle created potential reservoirs for shallow biogenic gas. From west to east across the Fort Peck Reservation in northeastern Montana, in a distance of 75 mi (121 km), the Judith River Formation changes from a 350-ft (107-m) accumulation of fine-grained nonmarine clastics, to a 130-ft (39-m) deposit of fine-grained sandstone. Three units are present in the subsurface of the central part of the reservation. A continuous basal sandstone, 30-130 ft (9-39 m) thick, formed in a coastal environment. This unit thickens in the direction of progradation, which may indicate the addition of sand bodies in a shelf environment. The middle unit is a 20 to 50-ft (6 to 15-m) sequence of shale and siltstone. Capping the Judith River is a sandstone 20-50 ft (6-15 m) thick, which formed either as a shore facies in the regressive cycle or as a shelf sandstone prior to the final Cretaceous transgression that deposited the overlying Bearpaw Shale. Stratigraphic traps exist in the upper and lower sandstone units due to variation in grain size and clay content associated with the progradational facies changes. In addition, Laramide structures associated with the Poplar dome and Wolf Creek nose have created local trapping mechanisms. Judith River gas has been produced for operational use since 1952 in the East Poplar field. Shows have been reported in central reservation wells, although high mud weights and deeper exploration targets have prevented adequate evaluation of the Judith River gas frontier.
- Research Organization:
- Fort Peck Tribes, Poplar, MT (USA)
- OSTI ID:
- 6123477
- Report Number(s):
- CONF-8808223-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 72:7; Conference: AAPG Rocky Mountain Section meeting, Bismarck, ND, USA, 21 Aug 1988
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hydrogeology of the Fort Peck Indian Reservation, northeastern Montana
Coastal and deltaic sedimentation of Upper Cretaceous Eagle Sandstone: relation to shallow gas accumulations, North-Central Montana
Related Subjects
MONTANA
NATURAL GAS DEPOSITS
EXPLORATION
CRETACEOUS PERIOD
GEOLOGIC FORMATIONS
GEOLOGIC TRAPS
SANDSTONES
SHALES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
MESOZOIC ERA
MINERAL RESOURCES
NORTH AMERICA
RESOURCES
ROCKS
SEDIMENTARY ROCKS
USA
030200* - Natural Gas- Reserves
Geology
& Exploration