Secondary recovery from a stromatoporoid buildup: Devonian Duperow Formation, Ridgelawn field, Montana

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6984562

Little, L D ^[1]

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1. Conoco Inc., Casper, WY (USA)

Ridgelawn field is located in Richland County, Montana, in the western part of the Williston basin. It is a multiple-pay field, with production from ordovician, Devonian, and Mississippian carbonates. Discovered in 1980, the field was recently unitized in the Devonian Duperow Formation for purposes of secondary recovery by waterflood. In this part of the Williston, the Duperow consists of a repetitive succession of shoaling-upward carbonate cycles, each deposited under increasingly restricted conditions on a shallow marine shelf. Production at Ridgelaw occurs from dolomites within one of these cycles, cycle IIIa. Three separate, laterally continuous porosity zones (here termed a, b, and c, from lowest to highest) are recognized and mapped individually in the field. The reservoir has a lensoidal geometry; porous dolomite thins and grades laterally into tight carbonate. The Duperow pool at Ridgelawn is a solution gas drive reservoir. Computer log analysis of the Duperow pay interval indicates an average true porosity of 11.8% and an average initial water saturation of 17.7%. Net pay, defined as greater than 5% crossplot porosity, averages 16.6 ft across the field. Petrographic analysis and log calibration suggests that different facies in each of the three porosity zones were preferentially dolomitized to create reservoir-quality rock; each is now a sucrosic dolomite with intercrystalline porosity. Porosity can be occluded (most often in the upper two zones b and c) by both calcite and anhydrite cements. The lowermost zone, a, is related to a stromatoporoid/coralline bank, and has excellent but highly variable porosity and permeability. The two upper zones, b and c, are more finely crystalline dolomite and represent shallower water depositional facies. Maps for each zone, including porosity, porosity-feet, net pay, and water saturation were constructed and used for equity determination in the unit.

• OSTI ID: 6984562
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020300* -- Petroleum-- Drilling & Production
58 GEOSCIENCES
580000 -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
DATA ANALYSIS
DEVONIAN PERIOD
DOLOMITE
ENERGY SOURCES
ENHANCED RECOVERY
FEDERAL REGION VIII
FLUID INJECTION
FOSSIL FUELS
FUELS
GAS INJECTION
GEOLOGIC AGES
GEOLOGIC DEPOSITS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERAL RESOURCES
MINERALS
MONTANA
NORTH AMERICA
OIL FIELDS
OIL WELLS
OXYGEN COMPOUNDS
PALEOZOIC ERA
PERMEABILITY
PETROLEUM
PETROLEUM DEPOSITS
POROSITY
RECOVERY
RESERVOIR ROCK
RESOURCES
ROCKS
SEDIMENTARY ROCKS
USA
WATERFLOODING
WELL LOGGING
WELLS
WILLISTON BASIN