HPHT viscosities measurements of mixtures of methane/nitrogen and methane/carbon dioxide

Gas production worldwide has been steadily increasing over the past 15 years. This growing demand for natural gas is driving the E&P industry to look for new resources in previously unexplored and deeper areas, where High Pressure High Temperature (HPHT) reservoirs may be encountered. These are reservoirs that exhibit pressures greater than 10,000 psia and temperatures over 300 °F. Thus, more attention must be paid to gas properties at HPHT conditions.Among all gas properties, viscosity is seldom measured in the laboratory and typically estimated through correlations. At HPHT conditions, the reservoir fluids will typically be very lean gases (e.g. methane with some degree of impurity) and therefore the gas properties may differ from those at lower pressures and temperatures. Consequently, the accuracy of gas viscosity correlations that are not experimentally validated at HPHT conditions may be doubtful.A review of a large database of published viscosity data for pure methane and mixed hydrocarbons revealed that they are limited in terms of both experimental conditions and quantity, and in some cases their accuracy is unknown.New HPHT gas viscosity correlations were derived using a set of viscosities of pure methane (CH4), mixtures of methane/nitrogen (CH4/N2) and mixtures of methane/carbon dioxide (CH4/CO2) measured using an oscillating piston viscometer at HPHT conditions.

► An oscillating piston viscometer was used as a HPHT viscometer for all the work.
► We provided a set of viscosities of mixtures of CH4/N2 and CH4/CO2 at HPHT.
► We developed an HPHT gas viscosity correlation for mixtures of CH4/N2 and CH4/CO2.
► Published viscosity data for methane and mixed hydrocarbons does not cover HPHT.
► Available gas viscosity correlations are not valid for HPHT.