  The helium abundance of stars is a strong driver of evolutionary timescales,
however it is difficult to measure in cool stars. We conduct an asteroseismic
analysis of NGC 6791, an old, metal rich open cluster that previous studies
have indicated also has a high helium abundance. The cluster was observed by
Kepler and has unprecedented lightcurves for many of the red giant branch stars
in the cluster. Previous asteroseismic studies with Kepler data have
constrained the age through grid based modeling of the global asteroseismic
parameters ($\Delta\nu$ and $\nu_{\mathrm{max}}$). However, with the precision
of Kepler data, it is possible to do detailed asteroseismology of individual
mode frequencies to better constrain the stellar parameters, something that has
not been done for these cluster stars as yet. In this work, we use the observed
mode frequencies in 27 hydrogen shell burning red giants to better constrain
initial helium abundance ($Y_0$) and age of the cluster. The distributions of
helium abundance and age for each individual red giant are combined to create a
final probability distribution for age and helium abundance of the entire
cluster. We find a helium abundance of $Y_0=0.297\pm0.003$ and a corresponding
age of $8.2\pm0.3$ Gyr.
