Gas viscosity is one of the gas properties that is vital to petroleum engineering. Its role in
the oil and gas production and transportation is indicated by its contribution in the
resistance to the flow of a fluid both in porous media and pipes. Although viscosity of
some pure components such as methane, ethane, propane, butane, nitrogen, carbon
dioxide and binary mixtures of these components at low-intermediate pressure and
temperature had been studied intensively and been understood thoroughly, very few
investigations were performed on viscosity of naturally occurring gases, especially gas
condensates at low-intermediate pressure and temperature, even fewer lab data were
published. No gas viscosity data at high pressures and high temperatures (HPHT) is
available. Therefore this gap in the oil industry still needs to be filled.
Gas viscosity at HPHT becomes crucial to modern oil industry as exploration and
production move to deep formation or deep water where HPHT is not uncommon.
Therefore, any hydrocarbon encountered there is more gas than oil due to the chemical
reaction causing oil to transfer to gas as temperature increases. We need gas viscosity to
optimize production rate for production system, estimate reserves, model gas injection,
design drilling fluid, and monitor gas movement in well control. Current gas viscosity
correlations are derived using measured data at low-moderate pressures and
temperatures, and then extrapolated to HPHT. No measured gas viscosities at HPHT are available so far. The validities of these correlations for gas viscosity at HPHT are
doubted due to lack of experimental data.
In this study, four types of viscometers are evaluated and their advantages and
disadvantages are listed. The falling body viscometer is used to measure gas viscosity at
a pressure range of 3000 to 25000 psi and a temperature range of 100 to 415 oF.
Nitrogen viscosity is measured to take into account of the fact that the concentration of
nonhydrocarbons increase drastically in HPHT reservoir. More nitrogen is found as we
move to HPHT reservoirs. High concentration nitrogen in natural gas affects not only the
heat value of natural gas, but also gas viscosity which is critical to petroleum
engineering. Nitrogen is also one of common inject gases in gas injection projects, thus
an accurate estimation of its viscosity is vital to analyze reservoir performance. Then
methane viscosity is measured to honor that hydrocarbon in HPHT which is almost pure
methane. From our experiments, we found that while the Lee-Gonzalez-Eakin
correlation estimates gas viscosity at a low-moderate pressure and temperature
accurately, it cannot give good match of gas viscosity at HPHT. Apparently, current
correlations need to be modified to predict gas viscosity at HPHT. New correlations
constructed for HPHT conditions based on our experiment data give more confidence on
gas viscosity.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-12-8739 |
| Date | 2010 December 1900 |
| Creators | Ling, Kegang |
| Contributors | Falcone, Gioia, Teodoriu, Catalin |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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