Reservoir characteristics of Putnam zone (Silurian Interlake Formation) lithofacies, southwestern Williston basin

Conference · Sat Jun 01 00:00:00 EDT 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6093748

Inden, R ^[1]; Oglesby, C ^[2]; Byrnes, A ^[3]; Cluff, B ^[4]

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1. LSSI, Denver, CO (United States)
2. Bass Enterprises, Fort Worth, TX (United States)
3. Geocore, Loveland, CO (United States)
4. The Discovery Group, Denver, CO (United States)

Reservoirs in the Putnam zone (lower Interlake Formation) in the southwestern part of the Williston basin include oolitic-pellet dolomite grainstone, fossil-pellet grainstone, and a wide spectrum of reef-related, fossil-corral dolomite packstones and coral-stromatoporoid rudstone/boundstones. Each of these potential reservoirs has a unique pore system and, thus a different set of petrophysical properties which define their reservoir characteristics. Oolitic grainstones have a homogeneous intercrystalline-micro-crystalline pore system, whereas the fossil-pellet dolomite grainstone facies consists of separate mesovugs dispersed in well-interconnected intercrystalline porosity. Capillary pressure curves indicate that pore-throat heterogeneity is greater, and entry pressures lower, for reefal lithofacies than for pelletal grainstones. These curves also demonstrate why many of the producing fields tend to have high water cuts. In many oolitic-pellet grainstone units, irreducible water saturations of 10% would not be reached until a hydrocarbon column of 700 ft was reached. High water production characteristics are therefore expected because Red River/Interlake structures attain only 50-100 ft of closure. This, however, does not mean that Putnam is not an economic zone, especially as a secondary objective. Wells in Putnam and Crane fields, for instance, have reserves in excess of 300,000 bbl of oil. The reservoirs here may be dominated by the reef-related facies, which have an extremely high relative permeability to oil.

• OSTI ID: 6093748
• Report Number(s): CONF-9107109--
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:6; ISSN AABUD; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
DEVELOPED COUNTRIES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGY
LITHOLOGY
MINERAL RESOURCES
MONTANA
NORTH AMERICA
NORTH DAKOTA
PALEOZOIC ERA
PERMEABILITY
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
PORE PRESSURE
POROSITY
RESERVOIR ROCK
RESOURCES
SILURIAN PERIOD
USA
WILLISTON BASIN