  The HELP project focuses on the data from ESA's Herschel mission, which
covered over 1300$deg^2$ and is preparing to publish a multi-wavelength
catalogue of millions of objects. Our main goal is to find the best approach to
simultaneously fitting SEDs of millions of galaxies across a wide redshift
range to obtain homogeneous estimates of the main physical parameters of
detected IR galaxies. We perform SED fitting on the UV/NIR to FIR emission of
42 047 galaxies from the pilot HELP field: ELAIS N1. We use the latest release
of CIGALE, a galaxy SED fitting code relying on energy balance, to deliver the
main physical parameters such as $M_{star}$, SFR, and $L_{dust}$. We implement
additional quality criteria to the fits by calculating $\chi^2$ values for the
stellar and dust part of the spectra independently. These criteria allow us to
identify the best fits and to identify peculiar galaxies. We perform the SED
fitting by assuming three different dust attenuation laws separately allowing
us to test the impact of the assumed law on estimated physical parameters. We
implemented two additional quality value checks for the SED fitting method
based on $M_{star}$ estimation and energy budget. This method allows us to
identify possible objects with incorrect matching in the catalogue and peculiar
galaxies; we found 351 possible candidates of lensed galaxies using two
complementary $\chi^2$s criteria (stellar and IR) and $z_{phot}$ calculated for
the IR part of the spectrum only. We find that the attenuation law has an
important impact on the $M_{star}$ estimate (on average leading to disparities
of a factor of two). We derive the relation between $M_{star}$ estimates
obtained by different attenuation laws and we find the best recipe for our
sample. We also make independent estimates of the total $L_{dust}$ parameter
from stellar emission by fitting the galaxies with and without IR data
separately.
