Depositional Modeling of Detrital Rocks: With Emphasis on Cored Sequences of Petroleum Reservoirs

Studies of cores from both field and wildcat wells offer the opportunity to interpret subsurface rock sequences and relate them to surface sections, to calibrate mechanical logs with observed lithologies, and to use these data to enhance both field development drilling and wildcat exploration. The cored sequences of detrital rocks described in this core workshop are organized on the basis of depositional models, and presented sequentially down the depositional system through the continental environments to the shoreline zone, and, finally, to the shallow offshore and deeper water environments. Each of the depositional models is treated in separate sections in which diagrams, facies descriptions and terminology are presented that summarize the principal aspects of the model.
Rocky Mountain Association of Geologists — 1978 Symposium: Peoria Field, Denver Basin, Colorado—J Sandstone Distributary Channel Reservoir Available to Purchase
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Published:January 01, 1985
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CiteCitation
Cooper B. Land, Robert J. Weimer, 1985. "Rocky Mountain Association of Geologists — 1978 Symposium: Peoria Field, Denver Basin, Colorado—J Sandstone Distributary Channel Reservoir", Depositional Modeling of Detrital Rocks: With Emphasis on Cored Sequences of Petroleum Reservoirs, Robert J. Weimer, Karen W. Porter, Cooper B. Land
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Abstract
Delta plain sandstones of early Cretaceous age are important reservoirs for stratigraphic traps in the J sandstone in the Denver basin. Peoria field, discovered in 1970, is an excellent example of a field producing from a complex of distributary channels in the J interval. A stratigraphic model developed from outcrop studies (MacMillan and Weimer, 1976) was used to interpret logs and cores from the Peoria field.
Three types of channel-fill deposits are recognized which reflect depositional stages during development of the channel. Following the classification by Meckel (1972), the normal vertical sequence contains a lower active channel fill, a middle partial abandonment fill, and an upper abandoned fill. However, any one of the three types may be absent in a vertical sequence. In Peoria field only the active fill has good reservoir characteristics. The channels are narrow and linear, being 1500-2000 feet wide and 30 to 40 feet deep. The active fill may vary from 0 to 100 percent of the total channel fill.
Fine-grained channel margin (interdistributary) deposits were deposited in levees, crevasse splays, marshes or swamps, and marine and fresh water bays. Only the crevasse splay sandstones near channels have favorable reservoir characteristics.
The ability to recognize the difference between an impermeable fine-grained channel fill facies and a channel margin facies will aid significantly in predicting the occurrence and trend of potentially oil-productive active channel-fill sandstones.