--> Abstract: Petrology and Diagenesis of the Stockholm Sandstone (Morrowan), Southwest Stockholm Field, Kansas, by E. D. Pittman and R. W. Tillman; #90987 (1993).

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PITTMAN, EDWARD D., Consultant, Sedona, AZ; and RODERICK W. TILLMAN, Consultant, Tulsa, OK

ABSTRACT: Petrology and Diagenesis of the Stockholm Sandstone (Morrowan), Southwest Stockholm Field, Kansas

Fluvial and, less importantly, tidal facies are productive from the quartz-rich (Q<93>F<1> L<7>) Stockholm Sandstone, which is the major reservoir for Southwest Stockholm field. In this heterogeneous, valley-fill reservoir the fluvial facies is coarse-grained, typically poorly sorted, and sometimes bimodal; whereas, the tidal facies is finer grained, more clay prone, and has good, but poorer reservoir characteristics than the fluvial facies. The fluvial facies averages 15.4 % porosity and 784 md permeability compared to 10.0% and 129 md for the tidal facies.

The major cements in the sandstone are: carbonate (7.7 %), which includes poikilotopic calcite and coarse, baroque, ferroan dolomite; kaolinite (4.9 %) as void fill and as replacement of feldspar; and quartz (3.2 %) as overgrowths. Authigenic minerals of less importance are: pyrite, chlorite, barite, siderite, and feldspar. The suggested sequence of precipitation is pyrite, chlorite, quartz, feldspar, calcite, barite, ferroan dolomite, siderite, and kaolinite. The Stockholm Sandstone has undergone chemical and physical compaction and has intergranular volumes of 20 to 26 %.

Textural evidence indicates a significant portion of the porosity is secondary. There are moldic pores outlined by laminar clay drapes of infiltration origin. Intergranular porosity is partially of secondary origin, and originated by dissolution of carbonate cement. Direct evidence for this is carbonate cement riddled with holes. Indirect evidence involves preservation of replacement textures imprinted by carbonate on quartz. For example, quartz grain outlines are ragged and even deeply embayed, and crystal faces on quartz overgrowths, which formed before carbonate cement, are commonly irregular and pitted.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.