Nanometer-Scale Authigenic Quartz Associated with Algal Bituminite and Intraorganic Nanoporosity in the Devonian Marcellus Shale: Observations and Hypotheses

The petroleum industry’s use of horizontal drilling and hydraulic fracturing technologies has changed organic-rich mudstones, like the Devonian Marcellus Formation, from conventional hydrocarbon sources and seals to unconventional ‘shale gas’ reservoirs. Organic-richness and formation brittleness are two principal components of reservoir quality assessment, as the former is indicative of the amount of hydrocarbons present [1] [2], and the latter is indicative of hydrocarbon accessibililty via hydraulic fracturing [1]. Interestingly, organic matter is associated with authigenic quartz [3] [FIG. 1], a primary brittle component within mudstone; therefore the nature of the organic-quartz association is critical to better understanding shale gas reservoirs.