--> Abstract: Diagenesis and Porosity of Rodessa Limestone, Running Duke Field, Houston County, Texas, by Brian D. Keith; #90968 (1977).

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Abstract: Diagenesis and Porosity of Rodessa Limestone, Running Duke Field, Houston County, Texas

Brian D. Keith

The grainstone facies of the Rodessa at Running Duke field consists of ooids, Orbitolina, miscellaneous mollusk fragments, and a few peloids. Individual beds generally are made up of equally abundant Orbitolina grains and mollusk fragments or of abundant ooids and less abundant Orbitolina grains. The Orbitolina-mollusk grainstone has a rind cement coating all grains. In some places, the rind cement bridges between grains and fills finer intergranular porosity. A later sparry calcite cement partly fills the intergranular pore space. The ooid-Orbitolina grainstone has no rind cement coating the grains and has only isolated patches of sparry calcite cement among grains. This cement apparently is associated with skeletal grains. With compaction, individual grains in the Orbit lina-mollusk grainstone show interpenetration, fracturing, and spalling off of rind cement. The ooid grains in the ooid-Orbitolina grainstone reacted to compaction by deforming plastically and bending around adjacent grains.

Scanning-electron microscopy and mercury-injection analyses indicate that the Orbitolina-mollusk grainstone has a relatively course, unimodal pore system. The ooid-Orbitolina grainstone has a bimodal pore system with relatively large intergranular pores and relatively finer micropores within the ooid grains. Both types of grainstones have the same range of total porosity and permeability, but have undergone a different diagenetic history.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC