Crisman Annual Report 2009 - Harold Vance Department of ...

Measurement of Gas Viscosity at High Pressures and High Temperatures
Introduction
Gas viscosity is an important fluid property in
petroleum engineering due to its impact in oil
and gas production and transportation where it
contributes to the resistance to the flow of a fluid
both in porous media and pipes. Although this
property has been studied thoroughly at low to
intermediate pressures and temperatures, there is a
lack of detailed knowledge of gas viscosity behavior
at high pressures and high temperatures (HPHT) in
the oil and gas industry.
The need to understand and be able to predict
gas viscosity at HPHT has become increasingly
important as exploration and production has moved
to ever deeper formations where HPHT conditions
are more likely to be encountered. Knowledge of
gas viscosity is required for fundamental petroleum
engineering calculations that allow one to optimize
the overall management of an HPHT gas field and
to better estimate reserves. Existing gas viscosity
correlations are derived using measured data at low
to moderate pressures and temperatures, i.e. less
than 10,000 psia and 300°F, and then extrapolated
to HPHT conditions. No measured gas viscosities at
HPHT are currently available, and so the validity of
this extrapolation approach is doubtful due to the
lack of experimental calibration.
Objectives
The National Institute of Standards and Technology
(NIST) has developed a computer program that
predicts thermodynamic and transport properties
of hydrocarbon fluids, which allows comparison
of its values with those from correlations and
gives an insight into the current understanding of
gas viscosity correlations. Note that Viswanathan
modified the Lee, Gonzalez, and Eakin correlation
by using NIST values. The above review of existing
gas viscosity correlations reveals that there are
no measurements available at HPHT conditions.
Correlations derived from data at low to moderate
pressures and temperatures should not be simply
extrapolated to HPHT conditions without validation
against experimental measurements.
Our objectives are to measure the viscosity of four
naturally occurring hydrocarbon gases at various
pressures and temperatures, with emphasis on high
pressures and temperatures; use the measured
viscosities to check and extend an existing correlation
proposed by Lee et al.; use gas compressibility
factors to check and extend the gas compressibility
correlation equation proposed by Piper et al.; and
develop a new correlation to predict viscosity as a
function of composition, pressure, and temperature.
Approach
Our facility consists of a gas source, a gas booster
system, a measuring system, and a data acquisition
system. The measuring system is the Cambridge
SPL440 High Pressure Research Viscosity Sensor
that is tailored to measure gas viscosities at
HPHT conditions. This technology is based on an
electromagnetic concept, with two coils moving a
piston back and forth magnetically at a constant
force. The piston’s two-way travel time is then
related to the fluid’s viscosity by a proprietary
equation. The viscosity range for the system is 0.02
to 0.2 cp, with a reported accuracy of 1% of full
scale. The maximum operating pressure is 25,000
psig. The Cambridge ViscoLab PVT software was
used to record the measurements.
(continued on next page)
Project Information
3.2.4 Measurement and Correlation of Gas Viscosities at
High Pressures and High Temperatures
Contacts
Gioia Falcone
979.847.8912
gioia.falcone@pe.tamu.edu
Catalin Teodoriu
catalin.teodoriu@pe.tamu.edu
Kegang Ling
CRISMAN INSTITUTE
Crisman Annual Report 2009
73