Core and petrographic sequential analysis of organic-rich Shale

In this work, different samples from the unconventional gas-producing Barnett Shale, Fort worth Basin, Texas, USA have been subjected to a variety of sequential petrographic analysis techniques. The primary goal of this work is to develop best analysis procedures for such type of organic-rich shale, since size and color are of little help. The sample types include core and thin sections. The analysis has been conducted sequentially from core description, thin section imaging, examination with transmitted and reflected polarizing lights, electron microprobe to scanning electron microscope. Through the core description, color, contacts, ripples, reworking, bioturbation and fractures were noted. The ratios of clay to silt, biogenic and detrital quartz, abundance of calcite, diagenetic dolomite and pyrite minerals, fossil content, and micro sedimentary structures have been identified using petrographic analysis. Three types of micro to nano-porosity in the Barnett Shale (intergranular, fossil and organic matter) have been identified and imaged through sequential resolutions from polarizing, electron microprobe to scanning electron microscopes.