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Experience and Impact of Measuring Permeability on Intact Samples at Reservoir Conditions for Unconventional Shales

Rosen, Richard; Kosanke, Tobi; Sharf-Aldin, Munir; Mickelson, William; Patterson, Robert; Mir, Faraz; Paiangle, Meghana; Kurtoglu, Basak; Ramirez, Benjamin; Baker, Tom

Physical properties of rocks are controlled by composition and texture. Texture can be considered the result of the many geologic processes imposed upon a rock throughout time. This includes the effects of deposition and diagenesis. Pore systems, and how they connect, are intimately related to these processes. The science of Petrology is devoted to understanding these influences and provides the critical link between the geosciences and engineering applications. As such, it is a commonly held belief throughout the history of petroleum science that laboratory core measurements need to be made at representative conditions. This has always been accepted for conventional reservoirs and is no less true for unconventional ones.

Apparatus have been developed for both steady- and unsteady-state methods for nano-Darcy (nD) range fine-grained shale material. The steady state method is based upon a dual pump system at high pressure using super critical fluids. Super critical fluids have the unique advantage of having low viscosity and low compressibility. Low viscosity allows measureable flow rates and low compressibility minimizes the amount of time to achieve steady-state equilibrium by reducing the length of time of unsteady-state transients. Specially designed and configured pump systems, seals and sleeves reduce leak rates to allow Darcy permeability determination below 1 nD. In this report we present a summary of over 200 such measurements and additionally document many of the same reservoir mechanisms long known in conventional reservoirs: stress dependency for both matrix and fractures, hysteresis, and rate dependent skin. Taken together for dual porosity reservoirs composed of matrix storage feeding fracture systems forms the basis of simulation models matching field data. Examples are presented from Woodford, Haynesville, Bakken and Eagle Ford formations.

 

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