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Researchers in Oklahoma Peering into Shale Pores

Gas and oil reside in the shales, but how much, and at what price, are questions researchers at the University of Oklahoma (OU) hope to answer at a new oil and gas "center of excellence."

Scientific instruments provider FEI and the OU Mewborne School of Petroleum and Geological Engineering (MPGE) are collaborating to create the FEI-OU Pore Scale Characterization Laboratory. Research will focus on development of routine quantitative methods to classify shales in the economic assessment of tight oil and gas plays.

"There has been tremendous growth in the development of oil and gas found in unconventional shale reservoirs," said MPGE professor Carl Sondergeld. "Unlike conventional reservoirs, the pores that hold the oil and gas in shales are very small and poorly connected -- hence the term 'tight.' Petroleum engineers would say they have low porosity and low permeability, making it difficult to extract any hydrocarbons that might be present.

"FEI's tools allow us to see the pores and organics directly, view the material they contain and actually reconstruct three-dimensional (3D) models of the pore network. The challenge now is to relate these nanometer-scale features to the large-scale geological and petrophysical characteristics that determine the economic potential of a particular reservoir."

FEI hopes to further develop its position as a supplier of high-resolution imaging solutions to the oil and gas industry by better defining and expanding its role in the characterization of unconventional reservoirs. Rudy Kellner, vice president of FEI's industry group said the company has much experience in the semiconductor manufacturing industry with process control and failure analysis.

"We would like to replicate that success as the leading provider of 'information from images' in the upstream oil and gas industry. Collaborating in the development of external resources, like this FEI-OU Pore Scale Characterization Laboratory, allows us to acquire a deeper understanding of the industry's challenges and our role in providing solutions."

Sondergeld said research will seek to link nano-scale observations to large-scale petrophysical parameters relevant to economic decision-making in the exploration and development of shale gas reservoirs.

Currently, predicting the potential value of tight gas discoveries is difficult, he said. "For example, hydraulic fracturing is largely a trial and error process. Better understanding of the parameters that govern fracturing may allow customization of materials and procedures based on the reservoir rock's microstructure and matrix composition to increase revenues and margins.

"As another example, initial production rates and decline rates are difficult to predict. Understanding the linkage between microscopic structure and petrophysical characteristics may support better choices of production sites and stage design."

Research into shale porosity has been ongoing at the university. Researchers at OU have been using a $2 million microscope to learn more about shale rock porosity. Sondergeld and his collaborators have found two kinds of pore space in the rocks. Besides inorganic pore space where one would expect to find gas, the research discovered pores the size of nanometers in the organic portion of the rock (see Shale Daily, Jan. 11, 2011).

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