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SHEPHERD, SUNDAY K., University of Texas at Austin, Department of Geological Sciences, Austin, TX

ABSTRACT: Depositional History and Reservoir Characterization of the Northeast Hardesty Field, Texas County, Oklahoma

The Northeast Hardesty Field in the Oklahoma Panhandle was developed in the early 1950s producing oil from the Morrow Formation. The lower part of the Morrow contains mixed clastic and carbonate shoreline sequences deposited during a marine transgression. The upper Morrow sandstones represent distributary channels on a prograding shoreline. The Morrow forms good hydrocarbon reservoirs, but vertical and lateral discontinuity, grain size variation, rapid facies changes and diagenesis make development challenging.

Upper Morrow production in Northeast Hardesty is from point bars and braid bars incised into the underlying sediments. The upper point bars show a fining upward pattern, small scale cross bedding, and wavy irregular ripple bedding. The mid point bars show larger scale festoon cross bedding. The lower point bars have coarse-grained channel lags and woody carbonaceous material.

The braid bars form stacked packages and show an overall upward coarsening pattern. The bars exhibit trough and planar cross stratification, small scale graded bedding and reactivation surfaces. Local scour surfaces, discontinuous lags and pebble sheets are common throughout.

Diagenesis has reduced the reservoir quality. Porosity and permeability have been decreased by cementation and compaction with clays clogging the pore throats and filling the pores themselves. Conversely, natural dissolution of chemically unstable detrital grains and authigenic cements has improved porosity and permeability in the reservoir.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid