Controls on Hydrocarbon
Entrapment and Reservoir Distribution:
The Pennsylvanian Oswego Limestone and Big Lime Limestone in the Putnam Field Area, Anadarko Basin, Oklahoma*
James R. Geary1
Search and Discovery Article #20046 (2008)
Posted March 27, 2008
*Adapted from presentation to the Houston Geological Society, North American Dinner Meeting, February 25, 2008
1Hess Corporation, Houston, TX ( [email protected] )
Putnam Field, located along the northern margin of the Anadarko Basin and extending through Custer and Dewey counties in western Oklahoma, USA, has produced over 400 BCF and 13 MMBO from the Pennsylvanian (Desmoinesian) Oswego Limestone and Big Lime. Hydrocarbons are stratigraphically trapped within phylloid algal mound complexes that are isolated within shallowing-upward parasequence sets; mound complexes generally trend west-east across the study area parallel to the northern structural margin of the Anadarko Basin. Reservoir quality within phylloid algal mounds is controlled by variations in the abundance of moldic, vuggy, and fracture pore types (average porosity = 2%, median permeability = 0.2 md). Eleven parasequence sets occur within the study interval and from the section base to top stack progradationally within the Oswego Limestone, and aggradationally to retrogradationally within the overlying Big Lime. The change from progradational to retrogradational stacking of parasequence sets most likely reflects an accelerating rate of subsidence during deposition that was induced by thrust-loading along the Ouachita foldbelt. Furthermore, retrogradational stacking within the Big Lime suggests that undiscovered hydrocarbon reserves may exist updip (northward) of the Putnam Trend in slightly younger deposits.
Detailed maps of structure, facies, gross pay, and pore volume were generated for each parasequence set, and compared with the spatial distribution of producing wells and their associated drainage radii. From these attributes, a geologic risk assessment was completed across the Putnam Trend to determine the most prospective areas for future step-out development.
· Twelve depositional facies were recognized.
· Accumulated within basinal and platform interior environments (subtidal, intertidal and mound). Reservoir quality is preferentially associated within algal mound facies.
· Facies were partitioned within eleven parasequence sets. Parasequence set stacking controls the spatial distribution of reservoir facies and hydrocarbon distribution.
Derstine, T.P., 1989, Sequence stratigraphy of the upper Desmoinesian Oswego Limestone along the northern hinge line of the Anadarko Basin, west-central Oklahoma: Southern Methodist University M.S. Thesis; also in Kenneth S. Johnson (ed.), Anadarko Basin Symposium: Oklahoma Geological Survey, Norman, Circular 90, p. 233-235.
Johnson, K. S., 1989, Geologic evolution of the Anadarko Basin, in Kenneth S. Johnson (ed.), Anadarko Basin Symposium: Oklahoma Geological Survey, Norman, Circular 90, p. 3-12.
Michlik, D.M., 1984, Petrographic and mapping study of the subsurface “Oswego” Limestone in part of the Putnam Trend, T 15-16 N, R 15-17 W, Dewey and Custer counties, Oklahoma, in Hyne, N.J. (ed.), Limestones of the Mid-Continent: Tulsa Geological Society Special Publication 2, p. 327-346.