--> ABSTRACT: Diagenetic History and Porosity Development of Triassic Arkosic Sandstones: Implications for Hydrocarbon Exploration, by Daniel G. Ziegler and Stephanie E. Kasza; #91038 (2010)

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Diagenetic History and Porosity Development of Triassic Arkosic Sandstones: Implications for Hydrocarbon Exploration

Daniel G. Ziegler, Stephanie E. Kasza

The Richmond basin of Virginia is one of several frontier Triassic basins of the Newark rift system of eastern North America currently being explored for hydrocarbons. There are numerous penetrations but limited core samples available for examination. In one well, however, 33 rotary sidewall cores have been collected and used for this study. Examination of these cores using thin section, X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques has revealed a complex diagenetic history for arkosic sandstones near potential hydrocarbon source beds. An atypical mineral assemblage has developed as a result of dissolution of feldspar, quartz, mafic silicate, and other minerals and subsequent precipitation of laumontite (a zeo ite), quartz, and trace amounts of clay. In thin section and with the SEM, these rocks have impressive intragranular and grain-moldic porosity and virtually no porosity-inhibiting clay. Consequently, a mechanism for creating significant secondary porosity in arkosic sandstones has been documented. This mechanism is probably related to the migration of hydrocarbons and associated fluids from source lithologies.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.