An extensive subsurface data base from the greater Red Wash area and outcrops 6-13 km from main producing areas are used to construct a high-resolution stratigraphic framework for the lower and middle part of the Eocene lacustrine Green River Formation. The correlation framework is based on the identification of a hierarchical set (4 scales) of depositional cycles that record temporal changes in the ratio of accommodation to sediment supply (A/S). Cycle stacking patterns (lakeward stepping, lakeward vertical stack, landward stepping and landward vertical stack) provide the chronostratigraphic framework to properly evaluate depositional facies and petroleum subsystems.

A petroleum system has a coherent source, migration, and trapping mechanism, however, such systems can be defined at many different scales. For exploration it is important to define these systems at a scale that can be used to rank plays. The stratigraphic framework is used to define subsystems within the basin-scale Green River Petroleum System. The stratigraphic hierarchy allows for ranking the extent and top sealing efficiency of open lacustrine shales deposited during lake-level highstands (maximum A/S). This hierarchy of top seals defines sets of petroleum subsystems at variable scales. Each petroleum subsystem has attributes that are described and cross referenced against other subsystems of similar scale. Between subsystems, attributes can be classified as common, similar, or different and critical or non-critical to the accumulation of hydrocarbons. In order to rank plays, exploration studies should focus on subsystem attributes that are critical and different. Attributes are scale dependent and need to be evaluated within the proper hierarchy.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah