Because of their fine-grained nature, shales exhibit substantially different reservoir properties than more conventional sandstone and carbonate reservoirs. New ideas and modified methods of reservoir characterization are required to reduce uncertainty in measuring volumetrics, drilling and stimulating a well, and gaining efficient production.
Over the past few years, our studies of unconventional gas shales in the U.S. mid-continent have led to establishing a workflow for stratigraphic characterization that addresses key issues in these unusual reservoirs. Proper characterization is multidisciplinary in nature. It includes (1) characterization of multi-scale sedimentology, litho- and sequence-stratigraphy, biostratigraphy, and geochemistry from cores, (2) relating stratigraphy to log response (including borehole image logs), (3) seismic response, (4) petrophysical and geomechanical properties, and (5) organic geochemistry. In addition, educational opportunities are being provided to university students who can then apply knowledge to petroleum industry careers. The result of this integration has led to better understanding of the evolution of shales and their contained gas, and regional to local mapping of key lithologic or stratigraphic intervals for improved drilling and production.