More Accurate Gas Viscosity Correlation for use at HPHT Conditions Ensures Better Reserves Estimation

Davani, E., Ling, K., Teodoriu, C., McCain Jr., W.D. and Falcone, G. (2009) More Accurate Gas Viscosity Correlation for use at HPHT Conditions Ensures Better Reserves Estimation. In: SPE Annual Technical Conference and Exhibition 2009, ATCE 2009, New Orleans, LA., United States, 4-7 Oct 2009, ISBN 9781615675753

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Abstract

High-pressure and high-temperature (HPHT) gas reservoirs are defined as having pressures greater than 10,000 psia and temperatures over 300°F. Modeling the performance of these unconventional reservoirs requires the understanding of gas behavior at elevated pressure and temperature. An important fluid property is gas viscosity, as it is used to model the gas mobility in the reservoir that can have a significant impact on reserves estimation during field development planning. Accurate measurements of gas viscosity at HPHT conditions are both extremely difficult and expensive. Thus, this fluid property is typically estimated from published correlations that are based on laboratory data. Unfortunately, the correlations available today do not have a sufficiently broad range of applicability in terms of pressure and temperature, and so their accuracy may be doubtful for the prediction of gas viscosity at HPHT conditions. This paper reviews the databases of hydrocarbon gas viscosity that are available in the public domain, and discusses the validity of published gas viscosity correlations based on their applicability range. A falling body viscometer was used in this research to measure the HPHT gas viscosity in the laboratory. The instrument was calibrated with nitrogen and then, to represent reservoir gas behavior more faithfully, pure methane was used. The subsequent measured data, recorded over a wide range of pressure and temperature, was then used to evaluate the reliability of the most commonly used correlations in the petroleum industry. The results of the comparison are presented here and suggest that at pressures higher than 8000 psia; the laboratory measurements drift from the National Institute of Standards and Technology (NIST) values by up to 7.48%. Finally, a sensitivity analysis was performed to assess the effect of gas viscosity estimation errors on the overall gas recovery from a synthetic HPHT reservoir, using numerical reservoir simulations. The result shows that a -10 % error in gas viscosity can produce an 8.22% error in estimated cumulative gas production, and a +10% error in gas viscosity can lead to a 5.5% error in cumulative production. These preliminary results indicate that the accuracy of gas viscosity estimation can have a significant impact on reserves evaluation.

Item Type:Conference Proceedings
Additional Information:Proceedings - SPE Annual Technical Conference and Exhibition, volume 5, 2009, pages 2954-2963.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Falcone, Professor Gioia
Authors: Davani, E., Ling, K., Teodoriu, C., McCain Jr., W.D., and Falcone, G.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
ISBN:9781615675753

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