--> ABSTRACT: Sequence Stratigraphic Control on Reservoir Quality in Morrow Sandstone Reservoirs, Northwestern Shelf, Anadarko Basin, by James Puckette and Zuhair Al-Shaieb; #90906(2001)

Datapages, Inc.Print this page

James Puckette1, Zuhair Al-Shaieb1

(1) Oklahoma State University, Stillwater, OK

ABSTRACT: Sequence Stratigraphic Control on Reservoir Quality in Morrow Sandstone Reservoirs, Northwestern Shelf, Anadarko Basin

Upper Morrowan valley-fill sandstones are major oil and gas reservoirs on the northwestern shelf of the Anadarko basin. Three major Morrowan lithofacies assemblages were recognized in cores and extrapolated from wire-line log responses: marine, fluvial and estuarine. Primary marine lithofacies are dark fossiliferous shale and bioclastic sandstone. Fluvial facies include channel-lag conglomerates, coarse-grained, cross-bedded sandstones and fine-grained sandstone, siltstone, shale, and coal. Estuarine facies are dominantly fine-grained sandstone and shale with abundant trace fossils.

Incised valleys developed in response to major drops in relative sea level. Lowstand system tract (LST) deposits were not commonly preserved and are limited to a few thin clay-clast conglomerates. Subsequent sea level rises resulted in valley filling with fluvial and estuarine facies of the transgressive systems tract (TST). Continued seal-level rise shifted sediment sources landward and the shelf became a starved margin setting characterized by deposition of marine silt and mud, which represents the highstand systems tract (HST) sediment assemblage. Although, no cores were available, distinct gamma-ray wire-line log signatures were interpreted as representing the maximum flooding surface (MFS).

Reservoir quality was influenced by compositional and textural parameters. Secondary porosity is the dominant type and resulted from dissolution of feldspars. Coarser-grained fluvial sandstones with minimal detrital clay retained primary porosity in addition to developing significant secondary porosity. Marine sandstones contain abundant skeletal grains and carbonate cement that occluded porosity. Finer-grained estuarine sandstones are typically poor-quality reservoirs due to high detrital clay content and the affects of biogenic modification that destroyed primary porosity.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado