Abstract

The Middle Pennsylvanian Bartlesville sandstone, a prominent oil producer in Oklahoma over the past 90 yr, is evaluated in terms of its sequence stratigraphic architecture over its occurrence in northeastern Oklahoma. The Bartlesville sandstone is interpreted to be a fluvial-dominated incised-valley fill deposited mainly during rising stages of relative sea level.

The incised paleovalley, as defined by relief along the sub-Bartlesville type 1 sequence boundary, extends for over 140 mi (225 km) in a north-south direction through Oklahoma, and exhibits widths ranging from 6 mi (9.7 km) in the north to 60 mi (96.5 km) in the south. Thickness of the Bartlesville sandstone ranges from 140-280 ft (42.7-85.3 m) within the paleovalley to less than 20 ft (6.1 m) outside the paleovalley. The lower Bartlesville sandstone represents the lowstand systems tract and consists of braided-fluvial deposits. The upper Bartlesville sandstone represents the transgressive systems tract and is dominated by meandering fluvial facies that transition down the paleovalley and stratigraphically upward to estuarine facies. The regionally extensive Inola Limestone Member marker, capping the Bartlesville sandstone, is equivalent to a condensed section representing maximum flooding. The Bartlesville sandstone is regarded as representing an underfilled incised valley when compared to the early sequence stratigraphy paradigm as both the lowstand and transgressive systems tracts are filled within the valley.

Original oil in place (OOIP) and reservoir quality are incorporated into the sequence stratigraphic architecture. The lowstand systems tract, which contains about two-thirds of the OOIP for many of the Bartlesville sandstone fields and reservoirs, has been the primary target of development over the past century and is nearly depleted. The transgressive systems tract, much more heterogeneous and less developed by comparison, offers the main potential for future development.

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