Distribution, thickness and reservoir properties of the lower Morrow Sandstone on the northern shelf of the Anadarko Basin in Harper, Woods and Woodward counties, Oklahoma

Scope and method of study. Wire-line logs for over 1500 wells across the townships (T. 24-27 N., R. 17-21 W.) in Woodward, Woods and Harper Counties, Oklahoma were acquired for analysis. The logs provided gamma-ray, resistivity, neutron-density porosity and bulk density signatures that were used to distinguish between strata of the Atoka, Morrow and the Chester intervals. Well data, including production information for the numerous wells across the area were also obtained for the study. Cross sections were constructed as well as structure, isopach and production maps to better understand the lateral extent, structure, distribution patterns, thickness and trends of the sandstones. Internal features and geometry of the lower Morrow sandstones were determined using core, thin section, and electron microprobe analyses.; Findings and conclusions. (1) Lower Morrow occupies a valley that erodes into the underlying Mississippian Chester. (2) Sandstone distribution patterns indicate north to south trends that suggest channel deposition. (3) Wireline logs indicate sand body geometry that fines upward and is in sharp contact with the underlying shale or carbonate. (4) The core contains sedimentary features such as channel lag conglomerate and planar and trough bedding, indicating fluvial deposition. (5) The lower Morrow sandstone is predominantly quartz, (quartzarenite) but contains chert and authigenic components including kaolininte, pyrite, calcite and dolomite. (6) Sandstone constituents determined by the thin section microscopy was confirmed using electron microprobe analysis. (7) The best reservoir properties (porosity and permeability) are in fluvial sandstone (average 15 % porosity and 253 md permeability).