Prediction and Distribution Analysis of Marcellus Shale Productive Facies in the Appalachian Basin, USA

Wang, Guochang; Carr, Timothy R.

In hydrocarbon exploration and development of unconventional shale oil and gas reservoirs the emphasis is often placed solely on organiccontent, but the productivity of shale reservoirsis also highly dependent on the ability of the rock to respond effectively to hydraulic stimulation. As to the result of the typical extremely low matrix permeability, higher potential gas productivity requires not only sufficient gas-in-place, but also a brittle mineralogy amenable to hydraulic fracturing (lower clay and higher carbonate and/or silica).We propose a quantitative method to characterize shale reservoirs in terms of both the organic richness and rock geomechanical properties. In the Marcellus Shaleand related units of the Appalachian basin, we have identifiedand quantifiedseven shale lithofacies based on mineral composition, rock geomechanical properties and organic-matter richness.

We develop an artificial neural networkthat uses a set ofderived petrophysical parameters typical of shale analysis as input variables to calibrate and train conventional logs to predict previously defined shale lithofacies based on the integration of limited core data andpulsed neutron spectroscopy (PNS) log suites. Spatial geostatistical analysis isused to develop a series ofexperimental variogram models and vertical proportion of each lithofaciesin order to construct a 3-D shale lithofacies realizations and a final geocellular model for the Marcellus Shale across the Appalachian basin. The 3-D lithofacies geocellular model is used to map the organic-rich facies and brittle facies at both regional and local spatial scales, and to examine individual wells. The most productive areas and horizons of Marcellus Shale are dominated by both organic-rich facies and brittle facies, which can berelated to the regional and local geologic controls.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013