Results from an Ongoing Study of TOC and Carbonate Content Analysis of the Ordovician Utica and Devonian Marcellus Shales, New York State
We are currently conducting extensive measurements from well cuttings of TOC and carbonate content from cuttings in wells in the Devonian Marcellus and Ordovician Utica Shale across New York State. The logs will have data points every ten feet starting above the organic rich interval and continuing into the clean limestone below organic-rich horizons. This poster will present the latest data in the form of cross sections and maps that show the vertical and lateral distribution of TOC and carbonate in these shale gas reservoirs. The goal of the research is to provide operators with hard data they can use to evaluate these plays.
The Marcellus Shale consists of organic-rich shale, with some thin organic-rich limestone beds overlain with organicpoor shale and underline by the Onondaga Limestone. Low organic gray shale occurs at the top of the Marcellus. The organic-rich section that is considered the play is a 50-300 foot-thick at the base of the Marcellus. The Cherry Valley Limestone, at the base of the Oatka Creek Formation, overlies the Union Springs Formation, and varies in thickness, organic content, and may consist of more than one significant limestone bed. The upper 20 feet of the Onondaga Limestone which underlies the Marcellus can commonly be organic-rich may contribute to reservoir volume.
The Utica Shale play actually consists of four different formations with varying amounts of calcium carbonate. The Lower I ndian Castle Shale is an organic-rich fissile black shale with a few limestone beds but relatively low carbonate content. The Dolgeville Formation is an inter-bedded limestone and shale with high carbonate content. The Flat Creek Shale is calcareous with moderate carbonate content. There are also organic-rich intervals within the Trenton Limestone that have very high carbonate contents.
The values for TOC and carbonate content from each sample will be used to make cross plots to determine if there is a relationship between the two for each formation.
AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009