Gas Viscosity Measurement and Evaluation for High Pressure and High Temperature Gas Reservoirs

Gas viscosity is an important fluid property in oil and gas engineering due to its impact on hydrocarbon production and transportation, reservoir recovery, fluid flow, deliverability, and well storage. Existing gas viscosity correlations were derived using measured data at low to moderate pressure and temperatures. No measured gas viscosities at high pressure high temperature (HPHT) using reservoir sample are currently available, and using the extrapolation approach is not reliable. Therefore, this research paper presents laboratory measurement of gas viscosity at HPHT and comparative study of some existing gas viscosity correlations using the measured data. The capillary electromagnetic viscometer was used to measure gas viscosity for pressures between 6,000 psia and 14,000 psia; and temperatures of 270 oF and 370 oF. The comparative study shows that the gas viscosity models commonly used in the industry are not very reliable at HPHT conditions. Ohirhian and Abu (2008) performed better than other evaluated correlations with the mean relative error of -5.22 and absolute error of 8.752 for the temperature of 270oF while Dempsey (1965) came out the best for the temperature of 370oF with mean relative error of -16.88 and 16.88 for absolute mean error. Cross plots showed the poor performance of the evaluated correlations using the measured data at HPHT conditions. From the analysis, the oil and gas industry needs new gas viscosity correlations that can predict gas viscosity at HPHT region