60th Annual Report on Research 2015

Characteristics of the Marcellus shale at high spatial resolution are the focus of this investigation. In particular, we document primary sedimentary characteristics and their relationships to today’s mechanical and chemical behavior of that unit. The scales of observation range from macroscopic features visible in New York State rock quarries and cores, to micron-scale features that require modern laboratory imaging. The observations are repeated for sedimentary columns separated by distances of hundreds of meters to tens of kilometers (hundreds of feet to tens of miles). The goal is to facilitate prediction of parameters that are important to efforts to minimize environmental impacts of fossil fuel production from shale. The availability of data has led to focus on the lower formation, the Union Springs, of the Marcellus Subgroup.

A Cornell University team containing the Principal Investigator, two geological sciences graduate students, and an undergraduate student participated in the study during 2014-2015, in collaboration with three faculty members and one graduate students from engineering disciplines. Growing collaborations with faculty members at two other colleges enabled access to additional core as well as to a deeper understanding of the relationships between faunal events and Marcellus paleo-environmental conditions. A core from southernmost New York, provided by a gas exploration company, was added to the quarry and core samples already in the process of analysis, such that we now have materials of varying resolution from 9 locations. An undergraduate has completed a preliminary investigation of these new materials in thin section, whereas the analyses by thin-section and SEM imaging of materials from the three quarry columns has been completed at a detailed level by one of the graduate students. Leaching experiments by the second graduate student progressed significantly, first mimicking the acid spear-heading stage of well completion. We are ready to conduct a second suite of leaching experiments, using simulated hydraulic fracturing fluid as the leachate. These experiments examine the relationships of primary sedimentary facies to leachate compositions.

We adopted a new focus on the distribution and types of microfossils, specifically dacryoconarid, a group of extinct zooplankton, in collaboration with a faculty member at Skidmore College. The objective is to tie the details of dacryoconarid diversity, first appearance, and last appearance data to the physical and chemical indicators of the environmental conditions of the Eifelian Appalachian epicontinental sea. In most of the Union Springs Formation of the distal basin margin, we have documented that the dominant mineral is calcite, and thus far work in progress leads to the working hypothesis that the dominant source of that calcite was dacryoconarid shells. Hence the focus on dacryoconarid not only ties our study of Union Springs properties to the behavior of the Devonian coupled biosphere – sedimentary facies, but also plausibly to the rock mechanical properties. In a series of preliminary experiments, the mechanical strength of the calcite comprising dacryoconarid shells has been compared to the mechanical strength of calcite in other types of fossils found within the Union Springs Formation as well as to calcite of diagenetic origin in the same rocks. This work continues.

Reports on results have been prepared for presentation at the 2015 Eastern Section AAPG meeting and at the 2015 Geological Society of America national meeting. A doctoral dissertation and a masters thesis are currently being written by the students based on this body of work.